MODEL 906

Battery “Fuel” Gauge

 Read Instructions Carefully!

®
SAFETY INSTRUCTIONS

This instrument was manufactured and tested according to the 

applicable technical standards. It complies with all the safety 

regulations as shipped from the factory.

Installation and startup must be performed by skilled personnel.

Failure to install and operate the unit in accordance with these 

instructions may result in damage or injury.

If safe operation of the instrument can no longer be ensured, 

stop and secure it against accidental operation.

If instrument failure or malfunction may cause personal injury 

or material damage, use additional safety measures such as 

limit switches, guards, etc.

Read the Operating Instructions carefully before startup.

Note the safety instructions marked with this 

warning symbol in this manual!
TABLE OF CONTENTS

1. Model Encodement 2

2. Technical Specifications

2.1 Electrical 6

2.2 Mechanical 6

2.3 Environmental 7

3. Installation 8

4. Operation

4.1 Display 9

4.2 Reset 10

5. Troubleshooting 11

6. Maintenance 12

7. Warranty 13
2

Example: Model 906 D 24 M C D A O

Case Style

Voltage

Reset

Discharge

Output

Special 

Options

1 3 5

2 4 6

Artwork

7

1 Case Style Options

12

24

36

48

Voltage 

Options

2

1. MODEL ENCODEMENT

D DIN case – rectangular

F Hex bezel w/1/4” spade terminals (enGage I)

J Hex bezel w/Packard connector (enGage I)

N DIN case - rectangular, snap-fit

P Pin mount (module)

R 52mm Round bezel & case (same as 700Q)

T Hex bezel w/3/16” spade terminals (enGage I)

TX Hex bezel w/3/16” spade terminals (old T case)

Y Rectangular bezel w/Packard connector (enGage I)

Z Rectangular bezel w/1/4” spade terminals (enGage I)
3

3 Reset Profile Options

Profile with 

Memory Option

Profile without 

Memory Option

Volts per Cell

OCR HVR CTR Full CTR 

Empty

K 1.928 2.167 2.167 2.10

J N/A 2.167

Y 2.083 2.167 2.167 2.10

N 1.980 2.230 2.230 2.10

E N/A 2.230

T 2.028 2.280 2.28 2.10

L N/A 2.280

D 2.060 2.320 2.32 2.10

P N/A 2.320

B 2.090 2.350 2.35 2.10

H N/A 2.350

C 2.135 2.400 2.400 2.10

M N/A 2.400

F N/A 2.416
4

4 Discharge Profile Options

Note: This gauge is not intended to measure the state-of-charge of batteries 

subject to extended periods of inactivity since it does not account for selfdischarge effects. Consult factory for details.

Letter Code Volts per Cell

Full Empty

G 1.97 1.75

H 1.97 1.70

J 1.97 1.63

K 2.01 1.65

L 2.10 1.92

M 2.00 1.83

N 2.04 1.73

P 2.08 1.98

Q 2.10 1.88

R 2.02 1.90

S 2.08 1.85

T 2.03 1.90

V 1.98 1.85

W 2.02 1.85

X 1.95 1.75

Y 2.00 1.90
5

Letter Code Logo

O Curtis

N None

Special Options

A = (TBD)

5 Output Options

6 7 Artwork Options

Letter 

Code Signal

A No option

B1 Both output & memory options 

C1 Both output & memory options and CTR reset instead of HVR

D Output option only

M Memory option only

1 option is for micro versions only
6

2. TECHNICAL SPECIFICATIONS

2.1 Electrical Operating Voltage

Operating Range: ±25% of nominal voltage

Operating Current

2.2 Mechanical Display

10-digit

Red LED

Tri-color (5 green, 3 yellow, 2 red)

Voltage

(VDC)

Nominal Current

(mA) 

Maximum Current 

(mA @B+ +25%) 

12 23 38

24 17 24

36 16 22

48 16 21
7

Recommended Panel Cutouts

F, J, T, TX, Y, Z Cases: 36.8 mm x 24.1 mm 

 +0.3/-.0mm

D, N Cases: 45.3 mm x 22.3 mm ±0.1 

R Case: 52.4 mm

Terminals 

D, N, T, TX: 3/16” blade 

R, F, Z: 1/4” blade

J, Y: 4-pin Packard Connector equivilent to 

 Delphi PN 15336035

P: Solder pins

2.3 Environmental Temperature

Operating: –40 to +85°C

Storage: –50 to +90°C

Humidity: 95% RH non-condensing at 38°C

Shock and Vibration: Meets SAE J 1378
8

3. INSTALLATION

Connecting Model 906

Pin 1 = Battery + 

Connects to the vehicle’s main positive (+) terminal. 

Use as short a wire as practical.

Pin 2 = Battery – 

Connects to the vehicle’s main negative (–) terminal 

Use as short a wire as practical.

Note: Pins 1 & 2 are connected across the total 

battery pack.

Pin 3 = Output Signal + or No Option

Output Signal option: 5 VDC ±0.5 VDC (90 μA 

current source) above Empty, 0-0.1 VDC at Empty 

1 VDC maximum (90 μA sink);

No Option: Pin 3 is left open.

Pin 4 = Keyswitch 

Connects to Battery + through the switched terminal 

of the keyswitch.
9

4. OPERATION

4.1 Display

1. Only when the battery is properly charged is the 

right-most LED lit. 

2. As the battery’s state-of-charge decreases, 

successive LEDs light up, only one on at a time.

3. The 2nd-from-left LED flashes, indicating “energy 

reserve” (70% depth of discharge).

4. The 2 left-most LEDs alternately flash, indicating 

“empty” (80% depth of discharge).

4

3

2

1

4 3

2

1
10

4.2 Reset

OCR (Open Circuit Reset) 

Upon reconnection of a battery the gauge will reset 

if it measures 2.09 volts/cell or higher (example “B” 

profile) (for units with memory option).

HVR (High Voltage Reset) 

Gauge must measure >2.35 volts per cell for 6 

continuous minutes during charging (example 

“B” profile).

CTR (Charge Tracking Reset)

Display tracks charge level during opportunity 

charging (requires gauge to be connected to 

battery when charging). 
11

5. TROUBLESHOOTING

The following checklist should help you troubleshoot any 

problem with Model 906.

Problem Possible Cause

Keyswitch on and no display Terminals not connected or improper voltage; 

Keyswitch not high

Stays at Full Model 906 voltage does not match battery 

voltage

Will not reset Model 906 voltage does not match battery 

voltage or battery not fully charged

Reset without terminals 

charging battery

Not connected directly to battery

Empty too soon Model 906 voltage does not match battery 

voltage or terminals not connected directly 

to battery
12

6. MAINTENANCE

Curtis Model 906 series is not field serviceable. Return

defective units to your distributor for warranty coverage.
13

7. WARRANTY

Curtis Instruments’ products and/or components are 

guaranteed against defects in workmanship and material for 

a period of one year, or as defined in the individual product 

literature, from date of shipment from our factory, when applied 

in a proper application within specified ratings. This guarantee 

is limited to repair or replacement F.O.B. our factory. There 

is no further warranty or implied representation, guarantee, 

promise or agreement as to any Curtis Instruments product 

and/or component. Curtis Instruments, Inc., cannot assume 

responsibility or accept invoices for unauthorized repairs to 

its products and/or components, even though defective. In no 

case will Curtis Instruments’ responsibility extend to products, 

components or equipment not of its manufacture. Under no 

circumstances shall Curtis Instruments, Inc., be liable for any 

special or consequential damages or loss of profits or other 

damages. Returned goods will not be accepted unless 

identified by a Curtis Return Material Authorization (RMA).

All specifications are subject to

change without notice.
CURTIS INSTRUMENTS, INC.

200 Kisco Ave.

Mount Kisco, New York 10549

914-666-2971 Tel

 914-666-2188 Fax 

www.curtisinstruments.com

53015 Rev. H 9/14