UB20.241/-C1
24V, 20A, DC-UPSUB-Series

DC-UPS CONTROL UNIT











No Change in Output Voltage in Battery Mode
Selectable Output Voltages in Battery Mode
1-Battery-Concept
Each 12V Battery is Charged and Monitored
Separately for Longest Battery Life
Precise Battery Charging by Using a Temperature
SensorBattery Size Selector for Small or Large Batteries
50% BonusPower®, 30A for up to 4s
High Breaking Capacity for Branch Protectors
Smart Battery Diagnostics and Monitoring Functions
3 Year Warranty

PRODUCT DESCRIPTIONSHORT-FORM DATAThe UB20.241 uninterruptible power supply controller(DC-UPS) is used in addition with a 24V power supply
and batteries to bridge power failures or voltage
fluctuations. This configuration can prevent expensive
downtimes, long restart cycles and loss of data.

Input voltage
Output voltage

A unique feature of the UB20 series is the constantvoltage in battery mode, which will not change as thebatteries discharge. The buffer voltage in battery modecan be set to four different output values. Anotherfeature is the utilization of two independent battery
chargers for the two 12V-batteries in series. This feature
makes matching batteries unnecessary and allows for
precise battery charging, testing and optimized usageof the battery capacity to achieve the longest battery
service life.

Output current

The UB20.241 includes many battery diagnostic
functions that ensure a reliable operation of the entire
system. Furthermore, a temperature controlled charging
extends the life of the batteries. It also includes a
selectable buffer time limiter as well as ready, bufferingand replace battery contacts. For safety andmaintenance, an inhibit input signal is included which
prevents a battery backup.

ORDER NUMBERS

Allowed battery
sizes
Buffer time

Temperature range
Derating
Dimensions
WeightDC 24V -±25%
same as input
voltage
22.5V, 24V, 25V,
26V (selectable)
25A continuous
30A for 4s
20A continuous
30A for 4s
3.9 – 150Ah

18-30Vdc
in power supplymode
in battery modein power supplymode
in battery modeat 22.5V
2 batteries inseries, each 12V
6min 45s
at 20A, 7Ah
16min 47s
at 20A, 12Ah
2h 49minat 20A, 65Ah
6h 20minat 20A, 140Ah-40°C to +70°C
operational
0.5A/°C+60°C to +70°C
46x 124x 127mm wxhxd
700g / 1.54lb

MAIN APPROVALS

DC-UPS

UB20.241
Standard DC-UPS unit
UB20.241-C1 Conformal coated pc-boards

Accessory

UZK24.071
UZO24.071
UZK24.121
UZO24.121
UZS24.100
ZM2.WALL
ZM12.SIDE

Battery module 24V, 7Ah
UZK24.071 without batteries
Battery module 24V, 12Ah
UZK24.121 without batteries
Sensor & center tap board
Wall/panel-mount bracket
Side-mount bracket

For details and the complete approval list, see chapter 19.

UL508

UL 60950-1

MarineMarineAug. 2021 / Rev. 2.4 DS-UB20.241-EN
All parameters are specified at 24V, 20A output current, 25°C ambient and after a 5 minutes run-in time unless otherwise noted.
www.pulspower.com Phone +49 89 9278 0Germany

Class I Div 2

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24V, 20A, DC-UPSUB-Series

INDEX
Page
1. Intended Use ............................................................. 3
2. Installation Instructions ............................................ 3
3. Input / Output ........................................................... 5
4. Batteries and Battery Charging ............................... 9
5. Buffer Time ............................................................. 11
6. Ready and Buffering Relay Contact ...................... 13
7. Replace Battery Relay Contact............................... 13
8. Inhibit Input ............................................................ 13
9. Efficiency and Power Losses................................... 14
10. Lifetime Expectancy and MTBF.............................. 14
11. Functional Diagram ................................................ 15
12. Terminals and Wiring ............................................. 15
13. Front Side and User Elements ................................ 16
14. EMC.......................................................................... 18
15. Environment ........................................................... 19
16. Protection Features ................................................ 20
17. Safety Features ....................................................... 20
18. Dielectric Strength .................................................. 21
19. Approved, Fulfilled or Tested Standards .............. 22Page
20. Regulatory Product Compliance............................ 23
20. Physical Dimensions and Weight .......................... 24
21. Accessories .............................................................. 25
21.1. ZM2.WALL - Wall-Mounting Bracket .......... 25
21.2. ZM12.SIDE - Wall-Mounting Bracket ........... 25
21.3. UZS24.100 - Sensor Board for DC-UPS ......... 26
21.4. UZK24.071 - 24V, 12AH Battery Module ..... 26
21.5. UZK24.121 - 24V, 12AH Battery Module ..... 27
22. Application Notes ................................................... 28
22.1. Battery Replacement Intervals ..................... 28
22.2. External Input Protection ............................. 30
22.3. Output Circuit Breakers ................................ 30
22.4. Back-feeding Loads....................................... 30
22.5. Parallel Use to Increase Output Current ..... 31
22.6. Parallel Use for Redundancy ........................ 31
22.7. Series Use for 48V Applications ................... 32
22.8. Using the Inhibit-Input ................................. 32
22.9. Troubleshooting ........................................... 33

The information presented in this document is believed to be accurate and reliable and may change without notice.
No part of this document may be reproduced or utilized in any form without permission in writing from the publisher.

TERMINOLOGY AND ABBREVIATIONS
DC-UPSPower supply mode

Battery mode
Normal mode
Buffer mode
Inhibit mode
T.b.d.
DC 24V
24Vdc
may
shall
shouldAbbreviation for Uninterruptible Power Supply system with a DC input and a DC output.
A DC-UPS utilizes batteries as back-up energy source.
Describes a condition where the input voltage is in the rated input voltage range and the
supplying power supply can deliver a sufficient amount of current for the DC-UPS and theload. Additionally it is assumed that the output is loaded within the allowed limits and thebattery is charged, if necessary.
The mode can also be called “Normal mode”.
Describes a condition where the input voltage is below the transfer threshold level, the unit
is running on batteries (buffering) and the output is loaded within the allowed limits.
The mode can also be called “Buffer mode”.
see “Power supply mode”
see “Battery mode”
Describes a condition where buffering is disabled on purpose (e.g. for service actions).
To be defined, value or description will follow later.
A figure displayed with the AC or DC before the value represents a nominal voltage withstandard tolerances included.
E.g.: DC 12V describes a 12V battery disregarding whether it is full (13.7V) or flat (10V).
A figure with the unit (Vdc) at the end is a momentary figure without any additional
tolerances included.
A key word indicating flexibility of choice with no implied preference.
A key word indicating a mandatory requirement.
A key word indicating flexibility of choice with a strongly preferred implementation.

Aug. 2021 / Rev. 2.4 DS-UB20.241-EN
All parameters are specified at 24V, 20A output current, 25°C ambient and after a 5 minutes run-in time unless otherwise noted.
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24V, 20A, DC-UPSUB-Series

1. INTENDED USEThis device is designed for installation in an enclosure and is intended for commercial use, such as in industrial control,
process control, monitoring and measurement equipment or the like. Do not use this device in equipment where
malfunction may cause severe personal injury or threaten human life.

2. INSTALLATION INSTRUCTIONSWARNING

Risk of electrical shock, fire, personal injury or death.

- Turn power off before working on the device and protect against inadvertent re-powering.
- Do not open, modify or repair the device.
- Use caution to prevent any foreign objects from entering into the housing.
- Do not use in wet locations or in areas where moisture or condensation can be expected.
- Do not touch during power-on, and immediately after power-off. Hot surface may cause burns.
Obey the following installation instructions:This device may only be installed and put into operation by qualified personnel.
This device does not contain serviceable parts. The tripping of an internal fuse is caused by an internal defect.
If damage or malfunction should occur during installation or operation, immediately turn power off and send unit to
the factory for inspection.
Turn power off and disconnect the battery fuse before working on the device.
Install the device in an enclosure providing protection against electrical, mechanical and fire hazards.
Install the device onto a DIN rail according to EN 60715 with the input terminals on the top of the unit.
The input can be powered from a regulated power supply or a similar DC source. The voltage between the input andground must not exceed 60Vdc continuously. The ripple voltage in the low frequency range between 50Hz and 10kHz
must be negligible when used in marine applications.
The input must be powered from a PELV or SELV source or an “Isolated Secondary Circuit” in order to maintain a SELVor PELV output.
Use an appropriately sized 24V power supply, which can deliver the additional internal current consumption, required
to charge the battery.
Use only VRLA lead acid batteries with a capacity between 3.9Ah and 150Ah.
Check for correct input and battery polarity. The device will not operate when the voltage is reversed.
Make sure that the wiring is correct by following all local and national codes. Use appropriate copper cables that aredesigned for a minimum operating temperature of 60°C for ambient temperatures up to +45°C, 75°C for ambient
temperatures up to +60°C and 90°C for ambient temperatures up to +70°C. Ensure that all strands of a stranded wire
enter the terminal connection.
Do not use wires smaller than 4mm2 (AWG 12) and not longer than 2x1.5m between the battery and the DC-UPS
controller. Longer or smaller gauge wires can change performance of the system.
Use a 35A fuse (ATOF® 287 035 from Little fuse or an UL listed fuse with the same characteristics) in the battery circuit.
The battery fuse protects the wires between the battery and the DC-UPS and shall be located close to the battery.
The device is designed for pollution degree 2 areas in controlled environments. No condensation or frost is allowed.
The device is designed as “Class of Protection III” equipment according to IEC 61140.
The enclosure of the device provides a degree of protection of IP20.
A disconnecting means shall be provided for the input and the battery input of the device.
The device is designed for convection cooling and does not require an external fan. Do not obstruct airflow and do notcover ventilation grid!
Aug. 2021 / Rev. 2.4 DS-UB20.241-EN
All parameters are specified at 24V, 20A output current, 25°C ambient and after a 5 minutes run-in time unless otherwise noted.
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UB20.241/-C1
24V, 20A, DC-UPSUB-Series

Keep the following minimum installation clearances: 40mm on top, 20mm on the bottom, 5mm left and right side.
Increase the 5mm to 15mm in case the adjacent device is a heat source. When the device is permanently loaded withless than 50%, the 5mm can be reduced to zero.
The device is designed for altitudes up to 6000m (19685ft). See additional requirements in the product datasheet for
use above 2000m (6560ft).
The maximum surrounding air temperature is +70°C (+158°F). The operational temperature is the same as the ambientor surrounding air temperature and is defined 2cm below the device.
The device is designed to operate in areas between 5% and 95% relative humidity.
The device is designed, tested and approved for branch circuits up to 28A without additional protection device.
Use a 25A melting fuse with a melting I2t of 400A2s – 1500A2s or a 25A circuit breaker with tripping characteristic B, C,
D or K on the input of the DC-UPS if the current of the power supply is higher than 28A.
Use a 4A fuse (ATOF® 287 004 from Little fuse or an UL listed fuse with same characteristics) between the connection
point of the two 12V batteries and the “Center Tap” connection point of the DC-UPS. An equivalent protection is
included on the original battery modules. The center tap connection is not mandatory but enables an individual
charging and monitoring of the two batteries.
Optionally, a PT1000 temperature sensor can be connected to terminals point 11 and 12 to measure the battery
temperature. This adjusts the charging voltage according to the battery temperature which extends the battery life.
This sensor is already installed in the original battery modules.
Installation Instructions for Hazardous Location Areas
The device is suitable for use in Class I Division 2 Groups A, B, C, D locations and for use in Group II Category 3 (Zone 2)
environments.
Hazardous Location Classification: ATEX: EPS 15 ATEX 1 025 X, II 3G EX ec nC IIC T4 Gc

WARNING EXPLOSION HAZARDS!
Substitution of components may impair suitability for this environment.
Do not disconnect the device or change unit settings unless power has been switched off or the area is known to be
non-hazardous.
A suitable enclosure must be provided for the end product which has a minimum protection of IP54 and fulfils therequirements of the EN 60079-0.
Fig. 2-1 Typical wiring diagram
24V
Non-bufferd
branches

Input Output

+

Bat1
12V

-

+

Battery

Bat2
12V

-

Buffered
Load

+

+

-

+

-

+

-

DC
Output++24V
bufferedbranches-

Nonbuffered
Load

UB20.241
Center Tap

UZK24

Temp. Sensor

Temp.
Sensor

24V Power
SupplyDC-UPS

optionalACInput
N L PE

24V Battery
ModuleAug. 2021 / Rev. 2.4 DS-UB20.241-EN
All parameters are specified at 24V, 20A output current, 25°C ambient and after a 5 minutes run-in time unless otherwise noted.
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24V, 20A, DC-UPSUB-Series

3. INPUT / OUTPUT
The output is connected to the input through a back-fed protection (MOSFET). In power supply mode, the output
voltage follows the input voltage decreased by a small voltage loss. In battery mode, the output voltage is a constantvoltage, which can be preselected in one of four voltages.
Input Voltage Range:
At voltages within the input voltage range, control functions such as LEDs, monitoring features, relay contacts, etc. arefunctioning normally. Within the input voltage range the unit can either be in power supply mode or in battery mode.
Normal Operating Voltage Ranges (four ranges):
The normal operating voltage range describes the input voltage, which supports the full functionality of the DC-UPS(including charging) but without entering the battery mode. It requires a minimum of 1V higher than the buffer
voltage settings and a maximum voltage of not more than 30Vdc.
Buffering and Buffer Voltage:
Buffering will start immediately without interruption after the input voltage falls below the lower end of the normal
operating voltage range. Buffering is possible even if the batteries are not fully charged.
Buffering can not be started without having previously entered the normal operating voltage range.
The buffer voltage is the output voltage determined by “the buffer voltage setting” and will not change as thebatteries discharge. The buffer voltage is pre-selectable in one of four voltages.
Fig. 3-1 Definition of “power supply mode” and “battery mode”
Input
VoltageTransfer Thresholdt
OutputVoltage
Power
SupplyMode

BatteryModePower
SupplyMode tFig. 3-3 Buffer voltage
Settings on the front

Fig. 3-2 Input Voltage Ranges
35V

Rated Input Voltage Range

30V

Buffer Voltage Settings
Four Ranges:
A
B
C
D
22.5V 24V 25V 26V
30V 30V 30V 30V
27V
26V
25V
23.5
V

Temporarily
allowed No Charging,no Buffering

Battery Mode

NormalOperating
Voltage(4 Ranges)

BufferVoltage
D: 26V
C: 25V
B: 24V

Range C

Range D

Range B
Range A

A: 22.5V

18V

0V

Aug. 2021 / Rev. 2.4 DS-UB20.241-EN
All parameters are specified at 24V, 20A output current, 25°C ambient and after a 5 minutes run-in time unless otherwise noted.
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24V, 20A, DC-UPSUB-Series

Input voltage
Input voltage range

nom.
nom.

DC 24V -±25%
18-30Vdc

max.

30-35Vdc

max.

35Vdc

typ.
typ.
typ.
typ.

23.5 – 30Vdc
25 – 30Vdc
26 – 30Vdc
27 – 30Vdc

typ.
typ.
typ.
typ.

23.5Vdc
25Vdc
26Vdc
27Vdc

Control functions such as LEDs, monitoring features,relay contacts, etc. are working. The unit can either bein power supply mode or in battery mode. See Fig. 3-2.
Temporarily allowed, no damage to the DC-UPS.
The red error LED will report “Input Voltage”, charging
and buffering are not possible. See Fig. 3-2.
Absolute max. voltage with no damage to the unit.
Ranges, where the unit does not switch to battery
mode. See Fig. 3-2.
Range A for a 22.5V buffer voltage setting
Range B for a 24V buffer voltage setting
Range C for a 25V buffer voltage setting
Range D for a 26V buffer voltage setting
Please note: The lower end must be at least 1V higher
than buffer voltages settings.
Range A, 22.5V buffer voltage
Range B, 24V buffer voltage
Range C, 25V buffer voltage
Range D, 26V buffer voltage

typ.

0.12V less than
input voltage
at 20A
22.5Vdc ±3%24.0Vdc ±3%25.0Vdc ±3%26.0Vdc ±3%

The output voltage is always slightly lower than the
input voltage, independent of the value of the input
voltage. See Fig. 3-4 and Fig. 3-5.
The buffer voltage is the output voltage in battery
mode, selectable in four steps via rotary switch on thefront of the unit and will not change as the batteries
discharge. See Fig. 3-2.

Normal operating input voltage
rangesTransfer voltage for switching
into battery mode

Output voltage
in power supply modein battery mode

Ripple and noise voltage
in power supply modein battery mode
Requirements for the power
supply on the input

Input current
internal consumption

nom.
nom.
nom.
nom.

max.

typ.
max.
max.

total input current

max.

not applicablebetter as the supplying power supply (filter included)
120mVpp20Hz to 20MHz, 50Ohm- Use an appropriately sized 24V power supply, which can deliver the
additional required internal current consumption of the DC-UPS and therequired current for charging the batteries. See also Fig. 3-6.
- Use power supplies that do not deliver more than 28A continuous
output current 1).
80mA
2.1A / 4.0A

When batteries are fully charged
For <10Ah / >10Ah settings; during battery charging,no temperature sensor installed
2.3A / 4.3A
For <10Ah / >10Ah settings; during battery charging,temperature sensor is installed
Sum of the output (load) current and the internal current consumption

Footnotes can be found on the next page.

Aug. 2021 / Rev. 2.4 DS-UB20.241-EN
All parameters are specified at 24V, 20A output current, 25°C ambient and after a 5 minutes run-in time unless otherwise noted.
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UB20.241/-C1
24V, 20A, DC-UPSUB-Series

Output current
in power supply mode

nom.
nom.
nom.

in battery mode

nom.
typ.
Overload behavior
in power supply modein battery mode
Output short circuit current
in power supply modein battery mode
Return current

typ.
typ.

Allowed voltage between input
and earth (chassis)
Capacitive and inductive loads
1)
2)
3)

4)

25A
30A
20A at 22.5V,
18A at 26V
30A at 22.5V,
26A at 26V
80A

Continuously allowed
For max. 5sContinuously allowed see Fig. 3-7(interpolate linearly between 22.5V and 26V)
For typ. 4s (BonusPower® 4)) see Fig. 3-7(interpolate linearly between 22.5V and 26V)
For typ. 25ms, output voltage stays above 20V,
(dynamic peak current), see Fig. 3-9.

not limited
HiccupPLUS Mode

Description see footnotes 1) and 2)
Description see footnote 3)

not limited
31A for 2 sec-200µA

Description see footnotes 1) and 2)
50mOhm impedance, repetitive pulses, see Fig. 3-8.
Leakage current to the input of the DC-UPS in battery
mode
continuous, IEC 62103

60Vdc or
42.4Vac
No limitation

max.

Use a 25A melting fuse with a melting I2t of 400A2s – 1500A2s or a 25A circuit breaker with tripping characteristic B, C, D or K on the inputof the DC-UPS if the current of the power supply is higher than 28A.
The DC-UPS has no current limiting feature included in power supply mode. The current is limited by the supplying power supply or the
fuse/ circuit breaker, which must be installed when the power supply has a continuous output current capability of more than 28A.
HiccupPLUS Mode:In battery mode, the DC-UPS can deliver 50% more output current for a period of up to 4s before it reduces the output current
automatically to the nominal output current. If the current requirement is continuously higher than the nominal current, the current
regulation of the DC-UPS reduces the output voltage. As soon as the output voltage falls below 18V, the output switches off and makes arestart attempt every 17s. This cycle is repeated as long as the overload exists.
BonusPower®:
The DC-UPS is designed to support loads with a higher short-term power requirement without damage or shutdown. In battery mode,the short-term duration is hardware controlled by an output power manager. At 150% output current, it is typically 4s and longer for
lower currents. Once the BonusPower® time is exceeded, the maximum output current is automatically reduced to the nominal output
current or the DC-UPS goes into the HiccupPLUS mode.

Fig. 3-5 Input to output voltage loss
measurement setup

Fig. 3-4 Input to output voltage loss
Input to Output Voltage Loss, typ.
180mV
A... 25°C
B... 60°C

150mV

B

120mV

A

90mV

Power
Supply+UIN

UB20.241

V Input

Output V-

60mV

Voltage Loss = UIN - UOUT

30mV
0mV

UOUT Variable
Load,
IOUT
0-25A
A

0

5A

10A

15A

20A
25A
Output Current

Aug. 2021 / Rev. 2.4 DS-UB20.241-EN
All parameters are specified at 24V, 20A output current, 25°C ambient and after a 5 minutes run-in time unless otherwise noted.
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UB20.241/-C1
24V, 20A, DC-UPSUB-Series

Fig. 3-6 Select an appropriate power supply,
which can deliver the additional current for
charging and internal consumption the DC-UPS

Fig. 3-7 Battery mode:
Output voltage vs. output current, typ.
Output Voltage

28V
Input
Current

OutputCurrent

22.5V

20Hiccupmode

128Current
consumption
for battery
charging

40

Output Current

0Fig. 3-8 Battery mode: HiccupPLUS behavior during
a short-circuit on output, typ.

4

8

12

16

20

24

28 32A

Fig. 3-9 Battery mode:
Dynamic peak current behavior, typ.
Output Voltage (dynamic behavior, < 25ms)

Output Current
Normalload

for 4s24
16

Internal
current
consumption

continuous

26V

Short circuit

Normal
load

28V
20

31A

26V

24
22.5V

16
12
t

0
2s

17s 2s17s

2s 17s840Output Current

0 10 20 30 40 50 60 70 80 90 100A

Aug. 2021 / Rev. 2.4 DS-UB20.241-EN
All parameters are specified at 24V, 20A output current, 25°C ambient and after a 5 minutes run-in time unless otherwise noted.
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24V, 20A, DC-UPSUB-Series

4. BATTERIES AND BATTERY CHARGINGThe battery is not included in the DC-UPS. Use one of the PULS 24V battery modules (see chapter 21.4 and 21.5). In
addition to the PULS battery modules, the UB20.241 is also designed to be compatible with a large variety of different
VRLA (Valve Regulated Lead Acid) or SLA (Sealed Lead Acid) batteries from various suppliers.
The battery is one of the most important parts of a DC-UPS system, which needs to be carefully selected while also
paying close attention to storage, charging and environmental conditions. Select the proper size (capacity) according
to the required buffer time (see chapter 5) and the lifetime requirements (see chapter 22.1).
Batteries are service parts and need to be replaced periodically or when the internal battery tests of the DC-UPS
reports a random failure. Information regarding the DC-UPS battery tests and the replacement requirements can befound in chapter 22.1.
The wiring from the battery to the DC-UPS must follow the instructions in chapter 2. Be aware that the current fromthe battery to the DC-UPS can be higher than the load current due to the buffer voltage transformation, which
restores the battery voltage to a constant buffer voltage.
The UB20.241 has a battery size selector included, which allows an optimal use of small and large battery sizes.
It is not recommended to connect multiple batteries or battery modules in parallel. Chose larger sized battery instead.
Charging:
The UB20 comprises a constant current / constant voltage (CC-CV) charging method.
When the center-tap connection is installed, both 12V batteries are charged individually with their own charger. The
center-tap connection is optional and if not installed, both batteries will be charged with one common charging
voltage. The UB20 automatically recognizes if the center-tap connection is present or not.
When charging is approximately 85% completed, the individual green “Ready” LED for the specific battery stops
flashing and is on solid.
During charging, the DC-UPS consumes additional current from the input. The supplying power supply must be able todeliver the additional required internal current consumption (including the charging current) specified as input current
in the table of chapter 3.
When the temperature sensor is installed, the end-of-charge-voltage is temperature compensated. The UB20
automatically recognizes if a temperature sensor is connected or not. In case no temperature sensor is installed, theend-of-charge-voltage is fixed to a value which corresponds to a battery temperature of 40°C.
Use a PT1000 temperature sensor or the PULS UZK24 battery modules, which have this sensor already included. A listof suitable PT1000 temperature sensors from different vendors can be provided.

nom.
nom.
typ.
typ.

small battery< 10Ah
3.9Ah – 10Ah 5)
24V
1.5A
2 x13.25V

large battery> 10Ah10Ah – 150Ah
24V
3A
2 x13.25V

typ.

26.5V

26.5V

Setting of battery size selector
Allowed battery sizes
Battery voltage
Battery charging current
End-of-charge-voltage

Temperature range for which
the charging process is enabled

typ.

2x 13.1 to 14.2V 1) 2x 13.1 to 14.2V 1)

typ.

26.2V to 28.4V 1)

26.2V to 28.4V 1)

nom.

-10°C to +50°C 2)-40°C to +50°C 2)

2x 12V batteries in series
In constant current mode
center-tap connected,
no temperature sensor connected
center-tap not connected,
no temperature sensor connected
center-tap connected,
temperature sensor connected
center-tap not connected,
temperature sensor connected

Footnotes can be found on the next page.

Aug. 2021 / Rev. 2.4 DS-UB20.241-EN
All parameters are specified at 24V, 20A output current, 25°C ambient and after a 5 minutes run-in time unless otherwise noted.
www.pulspower.com Phone +49 89 9278 0Germany

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24V, 20A, DC-UPSUB-Series

Setting of battery size selector- ctd.
Deep-discharge protection

Required min. battery voltage
to allow charging 3)
Battery charging time

Battery discharge current
1)
2)

3)
4)

5)

typ.

small battery< 10Ah
10.5V / 9.0V

large battery> 10Ah
10.5V / 9.0V

typ.

21V / 18V

21V / 18V

min.

2 x 7V

2 x 7VAt 0A / 20A buffer current,
center-tap connected,
Buffering stops as soon as one battery
falls below this value.
At 0A / 20A buffer current,
center-tap not connected
center-tap connected

min.
max.
max.
max.
max.
typ.

14V
4h 40mins 4)
8h 4)
44h 4)
94h 4)
170mA

14V
4h 4)
22h 4)
47h 4)
170mA

center-tap not connected
for a 7Ah battery
for a 12Ah battery
for a 65Ah battery
for a 140Ah battery
in battery mode at no output current

The end-of-charge voltage depends on the battery temperature. At 20°C the end-of-charge voltage is set to 13.6V (rsp. 27.2V) andchanges with -18mV/°C for 12V batteries and -36mV/°C for 24V batteries but not higher than 14.2V rsp. 28.4V.
Corresponds to the temperature readings of the external temperature sensor of the battery and is not the surrounding air temperatureof the DC-UPS. Frequent charging below +5°C (41°F) reduced the lifetime of the battery and should be avoided. Low temperatures
increase the battery impedance and also change the battery characteristics. This could result in a false “replace battery” signal or an
unexpected interruption of a buffer event, especially with small batteries. To avoid this, the temperature range for charging is limited at
low temperatures depending on the battery size. If the end application requires temperatures below +5°C, it is recommended to use
batteries >10Ah.
Below this voltage level, charging does not start and the DC-UPS reports “check wiring”.
The listed charging time applies for a complete discharged battery until the DC-UPS indicated “Ready” with the green status LED. In
practice, the charging time can be much shorter, since the battery is usually not completely discharged. A very long charging time is most
likely caused by a defective or old battery.
Batteries smaller than 6Ah are only recommended when the load current is below 10A.

Aug. 2021 / Rev. 2.4 DS-UB20.241-EN
All parameters are specified at 24V, 20A output current, 25°C ambient and after a 5 minutes run-in time unless otherwise noted.
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24V, 20A, DC-UPSUB-Series

5. BUFFER TIME
The buffer time (sometimes also called autonomy time) is the maximum period of time for which the battery canmaintain the required output current. The buffer time mainly depends on the capacity and quality of the battery andthe output current in battery mode.
The following times are typical values for a new product and the aging effect during operation is not included.
Pay attention:- The following buffer times apply for a battery temperature between 20°C and 30°C and a buffer voltage setting of
22.5V. At higher voltages, the buffer time is correspondingly shorter. Furthermore, with a wire length of 2x1m
(equal 1m cord length) and a cross section of 4mm2 (or AWG 12) between the battery module and the DC-UPS.
- Due to long-term aging effects of batteries consider a buffer time reduction of 30-50% over time.
- The shown buffer times only apply for PULS battery modules or from PULS recommended batteries.
- The buffer time is defined for a fully charged battery. The buffer time can be 10-20% shorter for buffer events,
which start immediately after the “Ready” signal becomes active.
7Ah

12Ah

(UZK24.071)(UZK24.121)

typ.
typ.
typ.
typ.
typ.
typ.
typ.
typ.
typ.

1d : 17h : 40m : 0s
17h : 13m : 20s
5h : 16m : 40s
2h : 32m : 0s
46m : 30s
19m : 11s
10m : 35s
06m : 45s
4s

2d : 22h : 50m : 0s
1d : 6h : 41m : 40s
9h : 51m : 40s
5h : 17m : 59s
2h : 2m : 55s
46m : 2s
27m : 34s
16m : 47s
4s

6d : 19h : 53m : 20s
2d : 20h : 03m : 20s
21h : 43m : 20s
11h : 27m : 30s
4h : 26m : 40s
2h : 10m : 0s
1h : 17m : 40s
55m : 00s
4s

At 22.5V, 0A
At 22.5V, 0.2A
At 22.5V, 1A
At 22.5V, 2A
At 22.5V, 5A
At 22.5V, 10A
At 22.5V, 15A
At 22.5V, 20A
At 22.5V, 30A

typ.
typ.
typ.
typ.
typ.
typ.
typ.
typ.
typ.

65Ah
16d : 10h : 26m : 40s
7d : 0h : 3m : 20s
2d : 4h : 21m : 40s
1d : 6h : 8m : 20s
11h : 56m : 40s
5h : 50m : 15s
3h : 49m : 17s
2h : 49m : 29s
4s

100Ah
24d : 7h : 20m : 0s
10d : 17h : 05m : 0s
3d : 11h : 20m : 0s
1d : 22h : 30m : 0s
18h : 30m : 40s
9h : 11m : 40s
6h : 3m : 0s
4h : 31m : 0s
4s

140Ah
34d : 17h : 20m : 0s
14d : 11h : 13m : 20s
4d : 21h : 21m : 40s
2d : 17h : 6m : 40s
1d : 1h : 55m : 0s
12h : 52m : 36s
8h : 27m : 44s
6h : 19m : 29s
4s

At 22.5V, 0A
At 22.5V, 0.2A
At 22.5V, 1A
At 22.5V, 2A
At 22.5V, 5A
At 22.5V, 10A
At 22.5V, 15A
At 22.5V, 20A
At 22.5V, 30A

Battery size
Buffer time

Battery size
Buffer time

26Ah

Fig. 5-1 Buffer time definition

Battery
Charge100%80-90%"Ready" signal thresholdt

BatteryMode
Buffer TimetAug. 2021 / Rev. 2.4 DS-UB20.241-EN
All parameters are specified at 24V, 20A output current, 25°C ambient and after a 5 minutes run-in time unless otherwise noted.
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24V, 20A, DC-UPSUB-Series

Fig. 5-2 Buffer time curves for battery modules UZK24.071 and UZK24.121, typ.
Buffer Current

20A
18A

Batteries:
A... 7Ah (UZK24.071)
B... 12Ah (UZK24.121)

16A
14A
12A
10A

A

B

8A
6A
4A

B

2A

A
0A
0

10

20

40

30

50

70

60

4

3
80
90 1,5 2
Hours
Minutes

6

5

7

8

9

10

Buffer Time

Fig. 5-3 Buffer time curves for various battery sizes, typ.

Buffer Current

20A
18A

Batteries:
A... 7Ah
B... 12Ah
C... 26Ah
D... 65Ah
E... 100Ah
F... 140Ah

16A

F

14A
12A

E

10A

D

8A
6A

C

4A

B
A

2A
0A
0

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

20 hours
Buffer Time

Aug. 2021 / Rev. 2.4 DS-UB20.241-EN
All parameters are specified at 24V, 20A output current, 25°C ambient and after a 5 minutes run-in time unless otherwise noted.
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24V, 20A, DC-UPSUB-Series

6. READY AND BUFFERING RELAY CONTACT
The DC-UPS is equipped with two independent relay contacts for remote monitoring and controlling of the unit.
Ready contact
Contact is closed when both batteries are charged more than typical 85%, no wiring failure is detected, input voltage
is sufficient and inhibit signal is not active.
Contact ratings
Isolation voltagemax.
60Vdc 0.3A, 30Vdc 1A, 30Vac 0.5A
min.
1mA at 5Vdc
see chapter 18.

resistive load
min. permissible load

Buffering contact
Contact is closed when unit is in battery mode.
Contact ratings
Isolation voltagemax.
60Vdc 0.3A, 30Vdc 1A, 30Vac 0.5A
min.
1mA at 5Vdc
see chapter 18.

resistive load
min. permissible load

7. REPLACE BATTERY RELAY CONTACT
The contact is closed when one of the battery quality tests of at least one battery reports a negative result.
To reset the “replace battery” signal, cycle the input power. The battery that has failed is indicated by the green LED
which is off. The battery should be replaced as soon as possible.
Contact ratings
Isolation voltagemax.
60Vdc 0.3A, 30Vdc 1A, 30Vac 0.5A
min.
1mA at 5Vdc
see chapter 18.

resistive load
min. permissible load

8. INHIBIT INPUT
The inhibit input disables buffering. In power supply mode, a static signal is required. In
battery mode, a pulse with a minimum length of 250ms is required to stop buffering. See
chapter 22.8 for details.

7+
3mA

Inhibit
5.1V

8-Signal voltage
Signal current
Inhibit threshold
Isolation voltage

max.
35Vdc
max.
6mA, current limitedmin.
6Vdc, buffering is disabled above this threshold level
max.
10Vdc
see chapter 18.

Aug. 2021 / Rev. 2.4 DS-UB20.241-EN
All parameters are specified at 24V, 20A output current, 25°C ambient and after a 5 minutes run-in time unless otherwise noted.
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24V, 20A, DC-UPSUB-Series

9. EFFICIENCY AND POWER LOSSES
Efficiency

typ.

99%

Power losses

typ.

1.9W

typ.

4.8W

typ.

6.8W

typ.

4.6W

typ.
typ.
typ.

4.2W
7.6W
21.3W

Power supply mode, 20A output current,
batteries fully charged
Power supply mode, 0A output current,
batteries fully charged
Power supply mode, 0A output current,
during charging batteries < 10Ah
Power supply mode, 0A output current,
during charging batteries > 10Ah
Power supply mode, 20A output current,
batteries fully charged
Battery mode, 0A output current
Battery mode, 10A output current
Battery mode, 20A output current

10. LIFETIME EXPECTANCY AND MTBF
Calculated lifetime expectancy*)

MTBF**) SN 29500, IEC 61709
MTBF**) MIL HDBK 217F

440 000h*)
1 244 000h*)
122 000h*)
345 000h
649 000h
1 097 000h
372 000h
498 000h

MTBF**) MIL HDBK 217F

107 000h
137 000h

Power supply mode, 10A and 40°C
Power supply mode, 10A and 25°C
Power supply mode, 20A and 40°C
Power supply mode, 20A and 25°C
Power supply mode, 20A and 40°C
Power supply mode, 20A and 25°C
Power supply mode, 20A and 40°C;
Ground Benign GB40
Power supply mode, 20A and 25°C;
Ground Benign GB25
Power supply mode, 20A and 40°C;
Ground Fixed GF40
Power supply mode, 20A and 25°C;
Ground Fixed GF25

The calculated lifetime expectancy shown in the table indicates the minimum operating hours (service life) and is determined by the
lifetime expectancy of the built-in electrolytic capacitors. Lifetime expectancy is specified in operational hours and is calculated according
to the capacitor’s manufacturer specification. The manufacturer of the electrolytic capacitors only guarantees a maximum life of up to 15
years (131 400h). Any number exceeding this value is a calculated theoretical lifetime which can be used to compare devices.
**) MTBF stands for Mean Time Between Failure, which is calculated according to statistical device failures, and indicates reliability of adevice. It is the statistical representation of the likelihood of a unit to fail and does not necessarily represent the life of a product.
The MTBF figure is a statistical representation of the likelihood of a device to fail. A MTBF figure of e.g. 1 000 000h means thatstatistically one unit will fail every 100 hours if 10 000 units are installed in the field. However, it can not be determined if the failed unit
has been running for 50 000h or only for 100h.
*)Aug. 2021 / Rev. 2.4 DS-UB20.241-EN
All parameters are specified at 24V, 20A output current, 25°C ambient and after a 5 minutes run-in time unless otherwise noted.
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24V, 20A, DC-UPSUB-Series

11. FUNCTIONAL DIAGRAM
Fig. 11-1 Functional diagram

DC- UPS+
24V
Power
SupplyInput

Back
Feeding
Protection+-

Battery
Charger1+ 12V -

Battery
Charger2

Current
LimiterCurrent
Measurement(7)(8)

Buck/Boost
Converter+

24V
BatteryCT

BAT1+ 12V BAT2

Buffered
Load

Output-Inhibit +Inhibit -Status LED Batt 1 (green)
Status LED Batt 2 (green)

Batt +

Diagnosis LED (yellow)(13)
CenterTap

Batt -

Controller

Error LED (red)Buffer Time Limiter

Battery
Diagnosis
1

Battery
Diagnosis
210s, 30s, 1m, 3m, 10m,

Buffer Voltage

22.5V, 24V, 25V, 26V(1)
Ready Contact(2)(3) Buffering(4) Contact

Temp. Sensor (11)(5)
Replace Battery(6)Temp. Sensor (12)Battery Size Selector<10Ah / > 10Ah

12. TERMINALS AND WIRING
The terminals are IP20 finger safe constructed and suitable for field and factory wiring.

Type
Solid wire
Stranded wire
American Wire Gauge
Max. wire diameter
Wire stripping length
Tightening torqueScrewdriver

Input and output
screw terminals
0.5-6mm2
0.5-4mm2
AWG 20-102.8mm (including ferrules)
7mm / 0.28inch
1Nm / 9lb.inch
3.5mm slotted or cross-head No 2

Signals
pluggable screw terminals
0.2-1.5mm2
0.2-1.5mm2
AWG 22-14
1.5mm (including ferrules)
6mm / 0.25inch
0.4Nm / 3.5lb.inch
3mm slotted

Instructions:a) Use appropriate copper cables that are designed for minimum operating temperatures of:
60°C for ambient up to 45°C and
75°C for ambient up to 60°C and
90°C for ambient up to 70°C minimum.
b) Follow national installation codes and installation regulations!
c) Ensure that all strands of a stranded wire enter the terminal connection!
d) Unused terminal compartments should be securely tightened or closed.
e) Ferrules are allowed.
Aug. 2021 / Rev. 2.4 DS-UB20.241-EN
All parameters are specified at 24V, 20A output current, 25°C ambient and after a 5 minutes run-in time unless otherwise noted.
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24V, 20A, DC-UPSUB-Series

13. FRONT SIDE AND USER ELEMENTS
Fig. 13-1 Front side

A Input Terminal (screw terminal)
B Output Terminal (screw terminal) One extra (-) pole for easy grounding.
The minus-pole is internally hard-wired with the minus-pole of the input and battery
terminals.
C Signal Connector (8-pole plug connector) comprises the following connections:- Ready relay contact, see chapter 6.
- Buffering relay contact, see chapter 6.
- Inhibit input signal, see chapter 8 and chapter 22.8.
- Replace battery, see chapter 4 and 7.
D Battery Terminal (screw terminal)
E

Battery Monitoring Connector (3-pole plug connector)- Connection for temperature sensor for battery temperature. See chapter 4 (optional).
- “Center-Tap” connection - middle point of the two batteries See chapter 2 (optional).

F

Red Error LED – This LED indicates that charging or buffering is not possible. The
flashing pattern reports the following reasons:- Check wiring- Insufficient input voltage- Too high temperatures
For details see Fig. 13-4.

G Yellow Diagnosis LED – This LED helps troubleshooting and the flashing patternindicates the following:- Output overloaded (current)- Battery replacement required- Expired buffer time due to buffer time selector or discharged battery- Activated inhibit input
For details see Fig. 13-3.
H Green Status LED – Each battery has its own status LED. Battery 1 represents thebattery, which is electrically closer to the (+) pole and battery 2, which is closer
to the (-) pole. The flashing pattern of this LED reports the following information:- Ready- Charging- Buffering
For details see Fig. 13-2.
I

Battery Size Selector (pluggable jumper) - For details see chapter 4.
Two positions to select battery sizes > and <10Ah. Influences the charging current, theallowed battery temperature range and the battery quality tests. Factory set: <10Ah.
A missing jumper equals a <10Ah setting.

J

Buffer Time Limiter (rotary switch with 6 dents) - For details see chapter 5.
Limits the maximum buffer time in a buffer event to save battery energy. Selectablebetween 10s 30s, 60s, 3 minutes and 10 minutes. If no limitation is selected (infinite
period of time), the buffering will be ended by the deep discharge protection.
Factory set: infinite.

K Buffer Voltage Selector (rotary switch with 4 dents) - For details see chapter 3.
Allows setting the output voltage in battery mode to 22.5V, 24V, 25V or 26V.
Factory set: 22.5V
L

Chassis Ground (screw)
Use a M4 ring-type terminal to connect the housing to ground, when required.

Aug. 2021 / Rev. 2.4 DS-UB20.241-EN
All parameters are specified at 24V, 20A output current, 25°C ambient and after a 5 minutes run-in time unless otherwise noted.
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24V, 20A, DC-UPSUB-Series

Fig. 13-2
Flashing pattern for green “Status LED”
1
0

Ready

1
0

Charging

1
0

10
Hz

Buffering

Each battery has its own status LED. The signals are thesame for both batteries.
Ready:The LEDs are on solid when the battery is charged (> 85%),
no wiring failure is recognized, input voltage is sufficient.
After the unit is turned-on with charged batteries, it cantake 20s or longer that the signal switches from charging
to ready.
Charging:
The LEDs are flashing with a low frequency when thebatteries are charging and the state-of-charge is below
85%.
Buffering:
The LEDs are flashing with a high frequency when the unit
is in battery mode.

Fig. 13-3
Flashing pattern for yellow “Diagnoses LED”
10

Overload

10

Replace
Battery10

Buffertime
expired10Inhibitactive5HzThis LED helps troubleshooting.
Overload:
The LED is on solid when the output current is permanently
above 20A in battery mode or 25A in power supply mode.
Replace Battery:
The LED is flashing with a low frequency when one battery
has failed the periodically performed battery quality test.
In case the center-tap connection is present, the battery
that has failed is indicated by the green LED which is off.
Otherwise, both LEDs are off. The battery should be
replaced as soon as possible.
Buffertime expired:
The LED is double flashing when the output has switched
off due to the setting of the buffer-time limiter ordischarged battery. This signal will be displayed for 15
minutes after the output has switched off.
Inhibit active:
The LED is flashing with a high frequency when buffering
is disabled due to an active inhibit signal.

Fig. 13-4
Flashing pattern for red “Error LED”

This LED indicates that charging or buffering is notpossible.

1
0

Check
Wiring10

Input
Voltage

1
0

Temp.

Check Wiring:
The LED is on solid when a failure in the wiring, battery orbattery fuse is identified.
Input Voltage:
A single flash indicates that the input voltage is >30V or
the input voltage is too low for the adjusted buffer
voltage. The input voltage must be at least 1V higher than
the selected buffer voltage.
Temperature:
A double flash indicates that the temperature of the DCUPS is too high (> 70°C) or that the temperature of thebattery is too high (> 50°C) or too low (< -10°C in setting<10Ah). Battery temperatures indications require aconnected battery temperature sensor.

Aug. 2021 / Rev. 2.4 DS-UB20.241-EN
All parameters are specified at 24V, 20A output current, 25°C ambient and after a 5 minutes run-in time unless otherwise noted.
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24V, 20A, DC-UPSUB-Series

14. EMCThe DC-UPS is suitable for applications in industrial environment as well as in residential, commercial and light industry
environment without any restrictions.
All tests are performed in power supply and battery mode.
EMC Immunity
Electrostatic discharge
Electromagnetic RF field
Fast transients (Burst)

Surge voltage on input
Surge voltage on output
Surge voltage on battery
and center-tap
Surge voltage on inhibit
input, ready-, bufferingand replace battery
contacts
Surge voltage on
temperature sensor
Conducted disturbanceAccording generic standards: EN 61000-6-1 and EN 61000-6-2
contact discharge*)
8kV
EN 61000-4-2
15kV
air discharge*)
EN 61000-4-3
80MHz-2.7GHz
10V/m
input lines
2kV
EN 61000-4-4
output lines
2kV
signals**)
2kV
+1kV
EN 61000-4-5+ / -  chassis ground
2kV
+1kV
EN 61000-4-5+ / -  chassis ground2kV+- ***)EN 61000-4-5+ / -  chassis ground
1kV
EN 61000-4-5
signals  chassis ground
1kV

Criterion A
Criterion A
Criterion A
Criterion A
Criterion A
Criterion A
Criterion A
Criterion A
Criterion A
Criterion A
Criterion A
Criterion A
Criterion A

EN 61000-4-5

signals  chassis ground

1kV

Criterion A

EN 61000-4-6

0.15-80MHz

10V

Criterion A*) Chassis ground connection earthed (grounded)**) Tested with coupling clamp***) Not relevant due to short wire length

Criterions:
A: DC-UPS shows normal operation behavior within the defined limits.
According generic standards: EN 61000-6-3 and EN 61000-6-4
limits for DC power ports acc.
IEC/CISPR 16-1-2, IEC/CISPR 16-2-1
input lines
EN 61000-6-3 fulfilledlimits for DC power ports acc.
IEC/CISPR 16-1-2, IEC/CISPR 16-2-1
output lines
EN 61000-6-3 fulfilled
IEC/CISPR 16-1-2, IEC/CISPR 16-2-1
battery lines-***)
Radiated emission
EN 55011, EN 55032
Class B
This device complies with FCC Part 15 rules.
Operation is subjected to following two conditions: (1) this device may not cause harmful interference, and (2) thisdevice must accept any interference received, including interference that may cause undesired operation.
EMC Emission
Conducted emission***) Not relevant due to short wire length

Switching Frequency

The DC-UPS has four converters included, three operate with the same switchingfrequency.
100kHzBuck-boost converter and battery charger
Auxiliary converter,
45 to 80kHz
switching frequency is input voltage dependentAug. 2021 / Rev. 2.4 DS-UB20.241-EN
All parameters are specified at 24V, 20A output current, 25°C ambient and after a 5 minutes run-in time unless otherwise noted.
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15. ENVIRONMENT
Operational temperature*)-40°C to +70°C (-40°F to 158°F)

Derating
Storage temperature
Humidity**)Vibration sinusoidal

2.5%/°C-40 to +70°C (-40°F to 158°F)
5 to 95% r.H.
2-17.8Hz: ±1.6mm; 17.8-500Hz: 2g***)2 hours / axis
30g 6ms, 20g 11ms***)3 bumps / direction, 18 bumps in total
0 to 6000m (0 to 20 000ft)
II
2

Shock
AltitudeOver-voltage category
Degree of pollution

Reduce continuous output current according
Fig. 15-1.
The operational temperature range can be
reduced by the battery specification. The DCUPS includes some safety features which
reduce the temperature range for charging.
See chapter 4 for details.
+60°C to +70°C (140°F to 158°F)
For storage and transportation
IEC 60068-2-30
IEC 60068-2-6
IEC 60068-2-27
Approvals apply only up to 2000m
IEC 62103, EN 50178, EN 60950, UL 840
IEC 62103, EN 50178, not conductive*)

Operational temperature is the same as the ambient or surrounding temperature and is defined as the air temperature 2cm below theunit.
**) Do not energize while condensation is present***) Higher levels are allowed when using the wall mounting bracket ZM2.WALL

Fig. 15-1 Continuous output current vs.
ambient temp.
Allowable Continuous Output Current

25A

a

20

b

15
10
5
0
-40

a Power Supply Modeb Battery Mode

-20

0

20

40

60 70°C

Ambient Temperature

Aug. 2021 / Rev. 2.4 DS-UB20.241-EN
All parameters are specified at 24V, 20A output current, 25°C ambient and after a 5 minutes run-in time unless otherwise noted.
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16. PROTECTION FEATURES
Output protection

Output over-voltage protection

Degree of protection

Penetration protection
Over-temperature protection

Input over-voltage protection
Internal input fuse
Reverse input polarity protection
Reverse battery polarity protection
Protection against wrong battery voltage
Battery deep discharge protection

In power supply mode:
The DC-UPS is protected by the current limitation of the supplying power
supply or a circuit protector on the input in case the power supply has anampacity greater than 28A.
In battery mode:
The DC-UPS is electronically protected against overload, no-load andshort-circuits
typ. 32Vdc
In case of an internal DC-UPS defect, a redundantmax. 35Vdc
circuit limits the maximum output voltage in battery
mode. The output shuts down and automaticallyattempts to restart.
EN/IEC 60529
IP 20
For use in a controlled environment according to CSA
22.2 No 107.1-01.
> 3.5mm
E.g. screws, small parts
included for
Output shuts down with automatic restart.
Additional temperature protection for charging ofbattery mode
batteries can be found in chapter 4.
max. 35Vdc
No harm or defect of the unitnoincludedmax. -40V
includedmax. -35Vdc
includedmax. +35Vdc
Buffering will stop when deep discharge protection is
includedactive. Battery will be disconnected from the DC-UPS.

17. SAFETY FEATURES
Input / output separation
Output voltage

Class of protection
Isolation resistance *)Touch current (leakage current)

The minus-pole is internally hard-wired with the minuspole of the input and battery terminals.
IEC/EN 60950-1,
SELV
The input must be powered from a SELV power source.
IEC/EN 60204-1, EN 50178, IEC 62103, IEC 60364-4-41,
PELV
The input must be powered from a PELV power source.
III
PE (Protective Earth) connection not required> 10MOhm
Power port to signal port
Power port to housing> 10MOhm
Signal port to housing> 10MOhm
The leakage current which is produced by the DC-UPS itself depends on the input
voltage ripple and need to be investigated in the final application. For a smooth DC
input voltage, the produced leakage current is less than 100μA.
not provided*) Center-tap terminal is categorized in the group of “power port”.

Aug. 2021 / Rev. 2.4 DS-UB20.241-EN
All parameters are specified at 24V, 20A output current, 25°C ambient and after a 5 minutes run-in time unless otherwise noted.
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24V, 20A, DC-UPSUB-Series

18. DIELECTRIC STRENGTH
The signal port (relay contacts and inhibit input) are floating and separated from the power port (input voltage,
output voltage, center-tap terminal and temperature sensor).
Type and factory tests are conducted by the manufacturer. Field tests may be conducted in the field using theappropriate test equipment which applies the voltage with a slow ramp (2s up and 2s down). Connect all poles of thepower port terminals together as well as all poles of the signal port before conducting the test. When testing, set the
cut-off current settings to the value in the table below. The following isolation tests were performed:
Type test

60s

A
1060Vac

B
1060Vac

C
1060Vac

Factory test

5s

650Vac

650Vac

650VacField test

5s

500Vac

500Vac

500Vac> 90mA

> 1mA

> 1mA

Fig. 18-1 Dielectric strength
Input, Output,
Battery,
Temperature
Sensor,Center-tap

A
ChassisCut-off current settingB

C
Signal Port

Aug. 2021 / Rev. 2.4 DS-UB20.241-EN
All parameters are specified at 24V, 20A output current, 25°C ambient and after a 5 minutes run-in time unless otherwise noted.
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24V, 20A, DC-UPSUB-Series

19. APPROVED, FULFILLED OR TESTED STANDARDSUL 508

IEC 60950-1

UL 60950-1

ATEX (UB20.241)

IECEx (UB20.241)

Class I Div 2 (UB20.241)

Marine (DNV)

Marine (ABS) (UB20.241)

IEC 60068-2-60

UL Certificate
Listed equipment for category NMTR - Industrial Control
Equipment
Applicable for US and Canada
E-File: E198865
CB Scheme Certificate
General safety requirements for Information Technology
Equipment (ITE)UL Certificate
Recognized component for category QQGQ - Information
Technology Equipment (ITE)
Applicable for US and Canada
E-File: E137006
Agency Certificate (Bureau Veritas)
EN 60079-0 Explosive atmospheres - General requirements
EN 60079-7, EN 60079-15 Equipment protection by type ofprotection "e" and "n"Certificate: EPS 15 ATEX 1 025 X
Temperature Code: T4
Type of Protection: ec nC
IECEx Certificate
IEC 60079-0 Explosive atmospheres - General requirements
IEC 60079-7, IEC 60079-15 Equipment protection by type ofprotection "e" and "n"Certificate: IECEx EPS 15.0049X
Temperature Code: T4
Type of Protection: ec nC
CSA Certificate
Power Supplies for Hazardous Location
Applicable for Canada and US
CSA Class: 5318-01 (Canada), 5318-81 (USA)
Temperature Code: T4
Groups: A, B, C and D
DNV Certificate
DNV Type approved product
Certificate: TAA00002JT
Temperature: Class D
Humidity: Class B
Vibration: Class C
EMC: Class A
Enclosure: Class A
ABS Design Assessment Certificate
ABS (American Bureau of Shipment) assessed product
Certificate: 17-HG1599236-PDA
Manufacturer's Declaration (Online Document)
Environmental Tests, Flowing Mixed Gas Corrosion Test
Test Ke - Method 4
H2S: 10ppb
NO2: 200ppb
Cl2: 10ppb
SO2: 200ppb
Test Duration: 3 weeks, which simulates a service life of 10 years

Aug. 2021 / Rev. 2.4 DS-UB20.241-EN
All parameters are specified at 24V, 20A output current, 25°C ambient and after a 5 minutes run-in time unless otherwise noted.
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24V, 20A, DC-UPSUB-Series

ISA-71.04 G3

VDMA 24364

Manufacturer's Declaration (Online Document)
Airborne Contaminants Corrosion Test
Severity Level: G3 Harsh
H2S: 100ppb
NOx: 1250ppb
Cl2: 20ppb
SO2: 300ppb
Test Duration: 3 weeks, which simulates a service life of 10 years.
Paint Wetting Impairment Substances Test (or LABS-Test)
Tested for Zone 2 and test class C1 according to VDMA 24364-C1L/W for solvents and water-based paints

20. REGULATORY PRODUCT COMPLIANCE
EU Declaration ofConformity

REACH Directive

WEEE Directive

KC Korean Certificate(UB20.241)
EAC TR Registration(UB20.241)

The CE mark indicates conformance with the- EMC directive- Low-voltage directive- RoHS directive
Manufacturer's Statement
EU-Directive regarding the Registration, Evaluation,
Authorization and Restriction of Chemicals
Manufacturer's Statement
EU-Regulation on Waste Electrical and Electronic Equipment
Registered in Germany as business to business (B2B) products.
KC Registration
Korean registration of Broadcasting and Communication
Equipment
Registered under Clause 3, Article 58-2 of Radio Waves Act.
EAC Certificate
EAC EurAsian Conformity - Registration Russia, Kazakhstan andBelarus8504408200, 8504409000

Aug. 2021 / Rev. 2.4 DS-UB20.241-EN
All parameters are specified at 24V, 20A output current, 25°C ambient and after a 5 minutes run-in time unless otherwise noted.
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24V, 20A, DC-UPSUB-Series

20. PHYSICAL DIMENSIONS AND WEIGHT
Width
HeightDepth

WeightDIN rail
Housing material
Installation clearances

46mm
1.81’’
124mm 4.88’’127mm 5.0’’
The DIN rail depth must be added to the unit depth to calculate the total required
installation depth.
700g / 1.54lb
Use 35mm DIN rails according to EN 60715 or EN 50022 with a height of 7.5 or 15mm.
Body: Aluminium alloy
Cover: Zinc-plated steel
See chapter 2

Fig. 20-1 Front viewFig. 20-2 Side view

Aug. 2021 / Rev. 2.4 DS-UB20.241-EN
All parameters are specified at 24V, 20A output current, 25°C ambient and after a 5 minutes run-in time unless otherwise noted.
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24V, 20A, DC-UPSUB-Series

21. ACCESSORIES
21.1. ZM2.WALL - WALL-MOUNTING BRACKETThis bracket is used to mount the DC-UPS onto a flat surface without utilizing a DIN rail.
Fig. 21-1 ZM2.Wall Wall mounting bracket*)Fig. 21-2 Wall mounting with DIN rail
brackets*)*) PSU for illustration purpose only.

21.2. ZM12.SIDE - WALL-MOUNTING BRACKETThis bracket is used to mount the device sideways with or without utilizing a DIN rail.
The two aluminum brackets and the black plastic slider of the unit have to be detached, so that the steel brackets canbe mounted.
For sideway DIN rail mounting, the removed aluminum brackets and the black plastic slider need to be mounted on
the steel bracket.
Fig. 21-3 ZM12.SIDE Side mounting
bracket *)Fig. 21-4 Side mounting with DIN rail
brackets *)*) PSU for illustration purpose only.

Aug. 2021 / Rev. 2.4 DS-UB20.241-EN
All parameters are specified at 24V, 20A output current, 25°C ambient and after a 5 minutes run-in time unless otherwise noted.
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24V, 20A, DC-UPSUB-Series

21.3. UZS24.100 - SENSOR BOARD FOR DC-UPSThe UZS24.100 enables all the benefits of the PULS 1-Battery-Concept when using
individual batteries and not one of the UZK24 battery modules. This sensor board
makes the use of matched batteries unnecessary and allows a precise battery
charging and testing resulting in the longest possible battery life. The sensor
board contains a PT1000 temperature sensor and an auto-resettable fuse which issuitable for charging currents up to 3.5A. The fuse protects the center-tap wire
between the battery module and the DC-UPS control unit.

21.4. UZK24.071 - 24V, 12AH BATTERY MODULEThe UZK24.071 passive battery module utilizes two non-spillable 7Ahmaintenance-free lead-acid batteries (connected in series), that areassembled in one package with all the required wiring included.
The battery module includes the monitoring and protection board
UZS24.100. This board contains a temperature sensor and a center-tap
connection with an auto-resettable fuse to protect the center-tap wire
between the battery module and the DC-UPS control unit. Connecting
the center-tap wire to the DC-UPS control unit enables all the benefitsof the PULS 1-Battery-Concept. This makes the use of matchedreplacement batteries unnecessary and allows a precise battery
charging and testing which results in the longest possible battery life.
The UZK24 battery module is available in two different options. It canbe ordered with assembled batteries (UZK24.071) or as a battery
bracket without batteries (UZO24.071), allowing for different battery
options. The mounting bracket option also allows the batteries to beassembled just in time, avoiding outdated batteries due to limited
shelf life.
Battery voltage
Battery capacity
Temperature sensor
Dimensions WxHxD
Weight UZK24.071 / UZO24.071

DC 24V
7Ah
PT1000137x186x143mm
6000g / 800g

Aug. 2021 / Rev. 2.4 DS-UB20.241-EN
All parameters are specified at 24V, 20A output current, 25°C ambient and after a 5 minutes run-in time unless otherwise noted.
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24V, 20A, DC-UPSUB-Series

21.5. UZK24.121 - 24V, 12AH BATTERY MODULEThe UZK24.121 passive battery module utilizes two non-spillable 12Ah
maintenance-free VRLA lead-acid batteries (connected in series), thatare assembled in one package with all the required wiring included.
The battery module includes the monitoring and protection board
UZS24.100. This board contains a temperature sensor and a center-tap
connection with an auto-resettable fuse to protect the center-tap
wire between the battery module and the DC-UPS control unit.
Connecting the center-tap wire to the DC-UPS control unit enables all
the benefits of the PULS 1-Battery-Concept. This makes the use ofmatched replacement batteries unnecessary and allows a precise
battery charging and testing which results in the longest possible
battery life.
The UZK24 battery module is available in two different options. It canbe ordered with assembled batteries (UZK24.121) or as a battery
bracket without batteries (UZO24.121), allowing for different battery
options. The mounting bracket option also allows the batteries to beassembled just in time, avoiding outdated batteries due to limited
shelf life.
Battery voltage
Battery capacity
Temperature sensor
Dimensions WxHxD
Weight UZK24.121 / UZO24.121

DC 24V
12Ah
PT1000203x186x143mm
9000g / 900g

Aug. 2021 / Rev. 2.4 DS-UB20.241-EN
All parameters are specified at 24V, 20A output current, 25°C ambient and after a 5 minutes run-in time unless otherwise noted.
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24V, 20A, DC-UPSUB-Series

22. APPLICATION NOTES
22.1. BATTERY REPLACEMENT INTERVALS
There are two main causes for battery failures and the need for replacing them:- Random failures:
Within the defined service life of a battery, random battery failures can happen. E.g. short circuit in one cell, broken
cell connection, acid pollution, mechanical defects, … . Such failures occur randomly and cannot be predicted. The
UB20 has various battery test features included, which periodically test both batteries individually and report such
failures. These battery tests include:- Battery presence test, performed every 10s- Battery dynamic impedance test, performed every 4hours- Charging time period (max. 40h in <10Ah settings and max. 170h in >10Ah settings)
Battery tests start as soon as the batteries are fully charged (the green status LED must be on solid). Battery dynamic
impedance tests need to fail several times in a row before “replace battery” is reported. This can take up to 14
additional hours after the batteries are fully charged.
- Wear-out failures:
The electrical characteristics of batteries degrade slowly over time. Main causes are chemical effects, which can becalculated. Therefore, battery manufacturers specify the design life of batteries to be able to calculate the expected
service time. The degradation of a battery cannot be easily tested on a running system. Therefore in addition to theresults from the battery tests of the UB20.241 (random failures), a periodical replacement is strictly recommended.
Service and design life of a battery:
Batteries have a limited service life and need to be replaced periodically. The service life depends on the grade of thebattery, which is expressed in the design life. The design life figures can be found in the individual datasheets of thebatteries and is usually specified according to the Eurobat guideline.
The design life is the estimated life, based on laboratory condition, and is quoted at 20°C using the manufacturer’s
recommended float voltage condition. According to the Eurobat guideline, design lives have been structured into thefollowing different groups:
3 - 5 years:

This group of batteries is very popular in standby applications and in small emergency equipment.
This represents a 4 years design life with a production tolerance of ±1 year.

6 - 9 years:

This group of batteries is usually used when an improved life is required.
This represents a 7.5 years design life with a production tolerance of ±1.5 years.

10 - 12 years: This group of batteries is used when in applications where longest life and highest safety level are
required. This represents a 11 years design life with a production tolerance of ±1 year.
If the operational parameters differ from those which are specified for the design life, an earlier replacement of thebattery might be necessary. The “real life” is called service life and is defined as the point at which the cell’s actual
capacity has reached 80% of its nominal capacity. At the end of the service life the capacity degrades much faster, sothat a further use of the battery is not recommended.
The degradation of a battery begins with the production date and not with the time when usage starts.
Effects, which shortens the service life of the battery and requires an earlier battery replacement:- Temperature:
The temperature has the biggest impact in the service life. The higher the temperature, the earlier the wear-out
phase of the battery begins. The wear-out results in a degradation of battery capacity. See Fig. 22-1 for details.
- Number of discharging cycles:
The number as well as the depth of discharging cycles is limited. A replacement of the battery might be necessary
earlier than the calculated service life if the battery exceeds the numbers and values of Fig. 22-2.
- Overcharging and deep discharging:
Overcharging and deep discharging shortens the service life and should be avoided. Due to the two individual

Aug. 2021 / Rev. 2.4 DS-UB20.241-EN
All parameters are specified at 24V, 20A output current, 25°C ambient and after a 5 minutes run-in time unless otherwise noted.
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24V, 20A, DC-UPSUB-Series

battery chargers and the temperature tracking feature of the UB20.241, the end-of-charge-voltage can be set very
precisely to the required value and thereby avoiding unnecessary aging effects.
- Discharged batteries:
Charge retention is important to get the longest battery life. Stored batteries which are not fully charged age fasterthen charged batteries. Batteries which are not in use should be recharged at least once a year.
- High ripple voltage:
Excessive float charge ripple across the battery has an effect of reducing life and performance. The UB20.241 does
not produce such a ripple voltage. This effect can be ignored when the battery is charged with the UB20.241.
Recommendations for achieving a long battery service life:- Place the batteries in a cool location: E.g. near the bottom of the control cabinet.
- Do not place the batteries near heat generating devices.
- Do not store discharged batteries.
- Do not discharge the batteries more than necessary. Set buffer time limiter to the required buffer time.
- When choosing the batteries capacity, always try to get the next higher capacity than required. The depth ofdischarge reduces the service life of the batteries and limits the number of cycles. See Fig. 22-2.
Fig. 22-1 Service life versus ambient
temperatures, typ *)Service Life in Years

10
9
8
7
6
5
4
3
2
1

20°C
*)

Cell Capacity

Design Lifeof Battery
A: 3-5 Years
B: 6-9 Years
C: 10-12 YearsC

Fig. 22-2 Battery capacity degradation vs.
discharging cycles *)

B

120%

C

100%
B

80%

A

60%

Depth ofdischarge
A: 100%
B: 50%
C: 30%

40%

A

20%

25°C

30°C

35°C

40°C 45°C

0

Ambient Temperature

200

400

600

800

1000 1200

Number of Discharging Cycles

Datasheet figures provided by the battery manufacturer

How to determine the replacement intervals:
Example:- Two 26Ah batteries with a design life of 10-12 years are used
- The average ambient temperature is 30°C
- One buffer event consumes approx. 25% of the achievable buffer time.
- One buffer event every two days (=182 cycles / year)
Calculation:A) Ambient temperature influence:
According to Fig. 22-1 curve C, a 5 years service life can be expected for an ambient temperature of 30°C.
B)

Number of discharging cycles: 5 years * 182 cycles = 910cycles in 5 years.
According to Fig. 22-2, curve C has to be used (only 25% of battery capacity is required). 910 cycles have only anegligible influence in a battery degradation and can be ignored.

Result:The battery shall be replaced after 5 years.
Please note that the battery degrading begins from the production date (check date code on the battery) which may
shorten the replacement intervals.

Aug. 2021 / Rev. 2.4 DS-UB20.241-EN
All parameters are specified at 24V, 20A output current, 25°C ambient and after a 5 minutes run-in time unless otherwise noted.
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24V, 20A, DC-UPSUB-Series

22.2. EXTERNAL INPUT PROTECTION
The DC-UPS is tested and approved for branch circuits up to 28A. An external protection is only required, if the
supplying branch has an ampacity greater than this. If an external fuse is necessary or utilized, minimum requirements
need to be considered to avoid nuisance tripping of the circuit breaker. A minimum value of 25A B- or C-Characteristic
breaker should be used.
Check also local codes and local requirements. In some countries local regulations might apply.

22.3. OUTPUT CIRCUIT BREAKERS
Some applications require branch circuit or branch circuit conductor protection on the 24V supply voltage. Therefore
standard miniature circuit breakers (MCB’s or UL 1077 circuit breakers) are commonly used on 24V branches.
MCB’s are designed to protect wires and circuits. If the ampere value and the characteristics of the MCB are adapted to
the wire size that is used, the wiring is considered as thermally safe regardless of whether the MCB opens or not.
To avoid voltage dips and under-voltage situations in adjacent 24V branches which are supplied by the same source, afast (magnetic) tripping of the MCB is desired. A quick shutdown within 10ms is necessary corresponding roughly tothe ride-through time of PLC's. This requires high peak currents to open the circuit breaker in the required time.
Furthermore, the impedance of the faulty branch must be sufficiently small in order for the current to actually flow.
For this discipline, two cases must be differentiated:A) DC-UPS is operating in power supply mode:
In this case, the supplying source is responsible for the peak current to trip circuit breakers. These values can befound in the datasheet of the power supply.
B)

DC-UPS is operating in battery mode:
The following table has typical test results showing which B- and C-Characteristic MCBs magnetically trip
depending on the wire cross section and wire length (setting for buffer voltage: 22.5V).
Fig. 22-3 Test circuit

MCB
DC-UPS
OutputLoad++
Wire length

S1

-

-

S1... Fault simulation switch*)

Maximal wire length*) for a fast (magnetic) tripping:
0.75mm²
1.0mm²1.5mm²2.5mm²
25m
34m
48m
72m
C-2A
C-3A
24m
32m
47m
68m
C-4A
18m
24m
33m
48m
C-6A
10m
12m
18m
28m
5m
6m
9m
13m
C-10A
C-13A
1m
2m
2m
3m
B-6A
23m
26m
32m
46m
B-10A
10m
14m
20m
31m
B-13A

9m

10m

18m

27m

B-16A

3m

4m

9m

13m

Don’t forget to consider twice the distance to the load (or cable length) when calculating the total wire length (+ and – wire).

22.4. BACK-FEEDING LOADS
Loads such as decelerating motors and inductors can feed voltage back to the DC-UPS. This feature is also called return
voltage immunity or resistance against Back- E.M.F. (Electro Magnetic Force).
This DC-UPS is resistant and does not show malfunctioning when a load feeds back voltage to the power supply. It
does not matter whether the DC-UPS is on or off.
The maximum allowed fed-back-voltage is 35Vdc.

Aug. 2021 / Rev. 2.4 DS-UB20.241-EN
All parameters are specified at 24V, 20A output current, 25°C ambient and after a 5 minutes run-in time unless otherwise noted.
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24V, 20A, DC-UPSUB-Series

22.5. PARALLEL USE TO INCREASE OUTPUT CURRENT
Two DC-UPSs with two individual power supplies, two battery modules and one decoupling module can be used tobuild a system with higher output current.
Fig. 22-4 Wiring example for parallel use to increase the output current

+

(13)
(12)
(11)

+ -

-

Center-tap
Temp.
SensorUZK24Battery
Module+ +- -DC 24V, 20A
OutputPower
SupplyAC Input
L N PE

+
IN

-

+

-

OUT

UB20.241
DC-UPS

-

+

(13)
(12)
(11)

Center-tap+

BAT+ - + IN 1 IN 2

Temp.
SensorYR40.241
UZK24
Battery
Module

+ -

OUT
+ -

Load

+

-

BAT

Inhibit

UB20.241
DC-UPS+

Replace
Battery-

OUT

Buffering

+

Ready

-

Inhibit

AC Input
L N PEIN

Replace
BatteryPower
Supply+Buffering- -DC 24V, 20A
Output

Ready

+ +

-

Ready
Buffering
Buffering
Inhibit22.6. PARALLEL USE FOR REDUNDANCY
Use the same schematic as for parallel use for higher output current Fig. 22-4 and follow additional the following
recommendations:
a)
b)
c)
d)
e)

Use separate input fuses for each power supply.
Set the power supply into “Parallel use” mode if available.
Use a redundancy module to decouple the two power sources.
Monitor the individual sources. Therefore, use the alarm contacts of the power supplies.
It is desirable to set the output voltages of all power supplies to the same value (± 100mV) or leave it at thefactory setting.

Aug. 2021 / Rev. 2.4 DS-UB20.241-EN
All parameters are specified at 24V, 20A output current, 25°C ambient and after a 5 minutes run-in time unless otherwise noted.
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24V, 20A, DC-UPSUB-Series

22.7. SERIES USE FOR 48V APPLICATIONS
A series connection for 48V applications is allowed when utilizing two individual power supplies, two DC-UPSs and twobattery modules.

-

+

OUT

(13)
(12)
(11)

Ready

AC Input
L N PE

Replace
Battery

UB20.241
DC-UPS

Power
Supply

-

-

+

BAT

+ +

- -

DC 24V, 20A
OutputCenter-tap
Temp.
SensorPower
SupplyUZK24Battery
ModuleAC Input
L N PE

+ -

+
IN

-

+

-

+

OUT

UB20.241
DC-UPS

-

+

BAT
(13)
(12)
(11)

-

Center-tap
Temp.
Sensor

-

48V
Load

UZK24
Battery
ModuleInhibit+Replace
Battery-

Buffering

IN

Ready

+

Inhibit- -DC 24V, 20A
OutputBuffering+ ++Fig. 22-5 Wiring example for 48V serial use+ -22.8. USING THE INHIBIT-INPUT
The inhibit input is a feature to disable the battery mode on purpose. This can be the case when buffering should
actively be stopped in order to save battery capacity (e.g. when machines are not in use for a long period of time) andto have shorter recharging times or in case of a service event, where the application must be turned off.
Buffering can be inhibited or stopped:-

When a static voltage is applied to the inhibit input terminals, there will be no buffering after the input voltage isswitched off.

-

When, during the battery mode, a short voltage pulse with a minimum length of 250ms is applied to the inhibit
input terminals, the output will switch off and stay off until the input voltage recovers.

Batteries will be charged when the inhibit mode is activated or a voltage is applied to the inhibit input terminals.
Electrical details of the inhibit input are specified in the chapters 8 and 18.
Fig. 22-6 Wiring example for inhibit input

Fig. 22-7 Activating the inhibit input
Case

A

Input
OutputBattery Mode

IN

+

-

OUT

+

-

BAT

+

-

-

Load

Inhibit

Ready

Case

B

UZK24
Battery
ModuleUB20.241
DC-UPS

Power
SupplyAC Input
L N PE-

Replace
Battery

DC 24V, 20A
Output+Buffering- -+Inhibit
+ +

+ -

250ms

Input
OutputInhibit

Case

C

Input
OutputInhibit not activated !
Battery Mode

InhibitAug. 2021 / Rev. 2.4 DS-UB20.241-EN
All parameters are specified at 24V, 20A output current, 25°C ambient and after a 5 minutes run-in time unless otherwise noted.
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24V, 20A, DC-UPSUB-Series

22.9. TROUBLESHOOTINGThe following guidelines provide instructions for fixing the most common failures and problems. Always start with themost likely and easiest to check condition. Some of the suggestions may require special safety precautions. See notes inchapter 2 first.
Symptom:

Explanation / Action:

Single flash on the “Error” LED-

Check input voltage.
The input voltage must be at least 1V higher than the selected buffer
voltage and smaller than 30V.

“Error” LED is solid on-

Check correct wiring between the battery and the DC-UPS-

Check battery fuse. Is the battery fuse inserted or blown?

DC-UPS did not buffer

DC-UPS stopped buffering

DC-UPS stopped buffering for 1s
DC-UPS constantly switches between
power supply mode and battery mode-

Check battery voltage (must be between 14.8V and 30V)-

Check battery polarity-

Inhibit input was set.

-Battery did not have enough time to get charged and the battery
voltage is still below the deep-discharge protection level.

-

Deep discharge protection stopped buffering. Use a larger battery, or
allow sufficient time for charging the battery.

-

End of service life of the battery-

Battery did not have enough time to be charged.

-

Inhibit input was activated-Buffer time limiter stopped buffering. Change the settings of the buffer
time limiter on the front of the unit.

-

At too high temperatures-

Center-tap connection opens in buffer mode-

Center-tap connection problems-

The supplying source on the input is too small and can not deliver
sufficient current. Use a larger power supply or reduce the output load.

-

The output voltage of the power supply dips to a too low value. The
input voltage must always be at least 1V higher than the selectedbuffer voltage and smaller than 30V.
Increase the output voltage of the power supply-

Too high voltage drops on wires. Increase the output voltage of thepower supply or increase the wires cross section from the power supply
to the DC-UPS.

Aug. 2021 / Rev. 2.4 DS-UB20.241-EN
All parameters are specified at 24V, 20A output current, 25°C ambient and after a 5 minutes run-in time unless otherwise noted.
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