Method and apparatus for determining battery type and modifying operating characteristics

A battery type detector for battery-using and battery-charging equipment is disclosed. Operational characteristics of the using and charging equipment are modified in accordance with the battery type detected.

BACKGROUND OF THE INVENTION 
This invention generally relates to the method and apparatus for 
determining the type of battery supplying power to battery operated 
equipment and being charged by battery chargers. This invention more 
particularly relates to a method and apparatus which will detect the type 
of battery connected to a circuit of the battery operated equipment on the 
basis of a predetermined voltage potential supplied at a test terminal of 
the battery and which will select one or more operating parameters for the 
using or charging equipment to optimize battery performance. 
Operationally, batteries of different types (such as those characterized by 
chemical components--Lithium, NiCd, Lead Acid, Alkaline, etc.--and those 
characterized as rechargeable or non-rechargeable) exhibit different end 
of life voltage characteristics and effective series resistances. Since 
different types of batteries can be interchangeably used to provide power 
for the same equipment (i.e. for a Cellular Portable Telephone), knowledge 
of the type of battery may be useful to the equipment in establishing 
operating parameters such as transmitter output power or in warning the 
user of a "low battery" condition. 
Nonrechargeable battery types should not be subjected to recharging 
attempts. Battery types that can be charged should be charged at differing 
rates and with differing conditions. A battery charger which accepts all 
battery types ideally should adapt the rate of charge (charge current) and 
the types of charge controls used in accordance with the battery type. 
Although it is known that the charge rate of a battery may be optimized in 
accordance with the charge capacity f the battery (U.S. Pat. No. 4,006,396 
discloses a battery and charger apparatus which employs an electrical 
element within the battery housing itself to provide a signed 
characteristic of the battery's charge state and which is employed by a 
charger circuit to control the rate of charge for the battery). This 
optimization is not changeable based on battery type and is limited to 
rate-of-charge determination. Therefore, it would be useful for a battery 
charger to automatically recognize the battery type which is to be charged 
and adapt its charging parameters accordingly. 
SUMMARY OF THE INVENTION 
It is, therefore, one object of the present invention to detect which type 
of battery is coupled to battery using or charging equipment. 
It is another object of the present invention to select and modify use 
parameters in battery powered equipment according to the type of battery 
connected. 
It is a further object of the present invention to select and modify charge 
control parameters in battery charging equipment according to the type of 
battery connected.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
This invention is particularly adapted for use in and with electrical 
equipment which can interchangeably couple to two or more different types 
of batteries. This equipment (for example, a portable radiotelephone) may 
"sink" power from a battery and deplete the battery charge. Alternatively, 
the equipment may be equipment which "sources" power to the battery in 
order to recharge the battery. The present invention is intended to power 
portable electronic equipment which provides low battery alerting to the 
user and which may vary the operational characteristics of the equipment. 
In a portable cellular radiotelephone, one operational characteristic 
which may be varied is that of transmitter power output level. The present 
invention is also intended to be used in battery chargers having the 
capability of charging two or more different battery types. 
A block diagram of a portable radiotelephone which may utilize the present 
invention is shown in FIG. 1. A battery 101 is shown coupled to a radio 
transceiver 103. There my be at least three electrical connections between 
the battery 101 and the transceiver 103; these connections supply primary 
battery power (105), ground (107), and sense input (109). Within the 
battery 101 is found a conventional electrochemical cell or cells 111 
which provide direct current electrical energy from a chemical reaction. 
The electrochemical cell type may be determined by capacity, effective 
resistance, physical construction, type of chemistry, or any other 
parameter pertinent to its use. A battery may have any number of like 
cells or combination of different cells. In some conditions, however, 
different batteries may have different characteristics but their use in a 
specific application may be identical enough for the batteries to be 
considered the same battery type. Nevertheless, when batteries of 
different characteristics perform differently in the specific application, 
they are considered herein to be different battery types. 
A sensing electrical component 113 (such as a resistor, a thermistor, an 
open circuit, a short circuit, or other elements which may provide 
auxiliary sensing capability) is utilized in the present invention to 
provide an electrical signature indication of battery type. In the 
preferred embodiment, the sensing element 113 is connected between sense 
input contact 109 and ground contact 107 of the battery 101, however, 
other connections may provide equally useful sensing capabilities. 
The transceiver 103 (which may be a model F09HGD8453AA portable cellular 
radiotelephone available from Motorola, Inc.) consists of a conventional 
radio transmitter 117 a conventional radio receiver 119, a user interface 
121 (which may further include an earpiece and microphone, dialing and 
control mechanisms, and visual and/or aural indicators such as an LED 
light or a bar graph on a display or a numerical indication of battery 
charge), logic and control functions 123 (which in a cellular portable 
radiotelephone of the aforementioned type may utilize a MC68HC11A8 
microprocessor or equivalent and associated memory and circuitry), and a 
battery type detector 125. 
The battery type detector 125 must be compatible with and capable of 
identifying the battery type electrical signature created with the 
selection of the electrical component 113 within the battery 101. The 
battery type detector 125 measures a sense input signal which is generated 
from a regulated voltage reduced in proportion to the ratio of resistor 
127 and the effective impedance of electrical component 113 in the battery 
101. The electrical component 113 is given a different electrical 
parameter value for each different battery type. Thus, in the preferred 
embodiment, the sense input is determined by the voltage divider formed by 
resistor 127 (having a resistance value of 15K Ohms) and resistor 113 
(having a value as shown in Table 1). Since resistor 113 is given a 
different value of resistance for each battery type, the sense input 
voltage is a different value for each battery type. Based upon the value 
of the sense input as measured by detector 125, the radio transceiver 103 
determines which battery type is connected and adjust its operating 
parameters accordingly. 
TABLE 1 
______________________________________ 
Component 
Battery Type 113 Value (Ohms) 
______________________________________ 
0 (manual test) 
.sup. 0-1K 
1 (NiCd) 1K-2K* 
2 2K-3K 
3 3K-5K 
4 5K-10K 
N (default) &gt;10K 
______________________________________ 
*thermistor 
One of the operating parameters which may be adjusted is that of the low 
battery alert which is provided to the transceiver user via user interface 
121. Conventionally, battery voltage is measured by the electrical 
equipment and when the battery voltage drops below a predetermined 
threshold, a light is lit or other indication is given to the user that 
the battery has reached the end of its useful battery charge. The 
equipment, typically, will be allowed to operate only for a limited 
duration after the low battery detection is made. A second battery voltage 
threshold may be included in a conventional circuit which entirely turns 
off the equipment thereby protecting such battery types as NiCd or lithium 
types which cannot be discharged below a certain charge without permanent 
damage to the electrochemical cells. Non-rechargeable batteries, however, 
do not require this minimum discharge voltage protection and can be fully 
discharged. A third battery alert parameter, the hysteresis voltage, may 
be included in a conventional circuit. Hysteresis is used to keep the unit 
from exiting low battery alerting when the equipment changes modes causing 
the battery discharge rate to change. This discharge rate change may 
change the battery terminal voltage enough so that it will now exceed the 
low battery alert voltage threshold and alerts will stop. By adding the 
hysteresis voltage to the low battery alert threshold voltage, the 
equipment will not exit low battery alerts. A second set of these voltage 
parameters may be used in a conventional circuit where there are two 
distinct modes of operation such as receive and transmit. Furthermore, 
different battery types have different characteristics of terminal voltage 
and amount of discharge (See FIG. 7.). Thus, a predetermined and fixed 
voltage threshold for indication of low battery charge or equipment turn 
off may be optimum for one battery type but non-optimum for another 
battery type. 
The output of detector 125, then, can inform logic and control function 123 
of the type of battery connected. Logic and control function 123 will scan 
its associated memory for one or more voltage threshold values which are 
optimum for the battery type connected and detected (See the first six 
rows of Table 2). Comparison of the battery voltage to the optimum 
established voltage thresholds may thus be used to provide a user 
indication of battery life at an optimum point determined by battery type. 
Similarly, other radio parameters may be adjusted in accordance with 
battery type. In the preferred embodiment of the invention used in a 
cellular portable radiotelephone, the output power of transmitter 117 can 
be adjusted to a maximum power level determined by the particular battery 
type connected to the radio transceiver 103. The mobile or portable 
subscriber equipment for cellular radiotelephone application has the 
capability of a plurality of transmitter output power levels, one of which 
is selected by the fixed site equipment. (see Fisher, "A Subscriber Set 
for the Equipment Test", Bell System Technical Journal, Vol. 58, No. 1, 
January 1979, pp. 123-143, showing early multiple transmitter output power 
level cellular equipment). Thus selection, which may be changed during the 
course of a radiotelephone call, is based upon the signal level received 
by the fixed site equipment. A received signal which is too strong will 
cause the fixed site equipment to command the mobile or portable to reduce 
the transmitter output power by one or more power level steps. Likewise, a 
received signal which is too weak will cause the fixed site equipment to 
command the mobile or portable to increase the transmitter output power 
level one or more step (up to a maximum output power for the class-mobile 
a portable - of subscriber unit). EIA Interim Standard, IS-3-D (March, 
1987), "Cellular System Mobile Station-Land Station Compatibility 
Specification" defines six 4 dB power level steps from -2 dBW to -22 dBW 
for portable radiotelephone equipment (paragraph 2.1.2.2). Each of these 
power level steps has a given tolerance or +2 dB/-4 dB from the nominal 
level. 
Although some radiotelephone systems place stringent minimum transmitter 
power output requirements on user equipment, other systems, may utilize 
the selectable transmitter output to enhance user equipment battery life. 
As the battery charge becomes depleted with use in the portable 
radiotelephone, the voltage available at the battery power contact 105 
decreases. Each battery type has a different voltage versus charge 
characteristic which is shown generally in FIG. 7. The control and logic 
function 123 (of FIG. 1) may utilize knowledge of the battery type derived 
from battery type detector 125 and component 113 to determine which 
battery type characteristic is expected and to adjust the transmitter 
output power maximum characteristics according to the battery charge 
remaining (as implied by the battery terminal voltage). Furthermore, the 
operational life of the battery may be extended by reducing the 
transmitter maximum output power level at particular battery charge levels 
depending upon battery type. In a preferred embodiment of the present 
invention, three power output levels are employed for some battery types. 
These unique transmitter output power features may be better understood 
while referring to the seventh row of Table 2. Thus a battery type having 
a voltage versus time characteristic exhibiting a sharp drop off of 
voltage output after a particular amount of battery charge depletion can 
have the transmitter maximum output power level maintained at the maximum 
transmitter output power level for a long period of time with subsequent 
power output reductions. A battery type having a relatively linear 
decrease in output voltage versus battery charge will have the transmitter 
output power level reduced sooner. 
Different battery types present different battery terminal voltage changes 
with changes in the load presented to the battery. When battery terminal 
voltage thresholds are established, the effect of load change must be 
considered and a hysteresis must be developed for the threshold battery 
terminal voltage. The value of battery load change hysteresis may be 
apprehended from FIG. 9. When the transmitter is operating, the battery 
terminal voltage decreases with time (curve 901). If the transmitter 
reduces its power output level at battery terminal voltage points 
determined in accordance with one aspect of the present invention, the 
reduced load on the battery will conventionally cause the battery terminal 
voltage to increase. Without hysteresis, such an increase in battery 
terminal voltage will cause the transmitter to reenter the higher power 
mode which causes the battery terminal voltage to decrease, etc. 
Hysteresis of the appropriate value for the particular battery type 
supplying power to the transmitter will prevent such a bistable oscillator 
from occurring. Thus, when the battery terminal voltage (901) reaches the 
voltage threshold (V.sub.th1) between transmitter output power level 1 and 
power level 2 (at 903), the transmitter is changed to power level 2. In 
accordance with one aspect of the present invention, the value of 
threshold V.sub.th1 is increased by the selected hysteresis value V.sub.n 
(as shown at 905). A similar threshold change occurs at point 907. 
Another radio parameter which may be adjusted in accordance with battery 
type is that of the state-of-charge indicator type. In the preferred 
embodiment of the invention used in a cellular portable radiotelephone, a 
state of charge indication is visually provided to the user via user 
interface 121. Conventionally, a battery state of charge indicator makes 
its determination of the amount of charge in the battery by the battery 
terminal voltage. It uses the battery terminal voltage to determine into 
which of a finite number of state of charge ranges the battery is in (such 
as 100%, 80%, 60%, 40%, 20%, or 0% of full charge). However, different 
battery types have different characteristics of terminal voltage relative 
to the percentage of charge left (see FIG. 7). Thus, a predetermined and 
fixed voltage vs. percentage of charge characteristic may be accurate for 
one battery type but inaccurate for another battery type. Thus, an 
important feature of the present invention uses a different voltage vs. 
percentage of charge characteristic for each battery type. The 
characteristic is selected based upon the battery type which is detected 
as previously described. 
An alternative charge state indicator is one which determines the state of 
charge by keeping track of the time the unit is used, calculating the 
amount of charge used, comparing the amount of charge used against the 
full capacity of the battery and providing the charge state to the user 
via user interface 121. The equipment being operated can draw different 
amounts of charge per unit time depending upon the battery type being used 
and different battery types may have different amounts of charge 
capacities. Thus, a predetermined and fixed calculation of charge state 
may be optimum for one battery type but non-optimum for another battery 
type. An alternative implementation of the present invention uses a 
selectable set of charge capacities and charge depletion rates for each 
battery type. 
A battery charger which may employ the present invention is shown in the 
schematic block diagram of FIG. 2. A battery charger such as charger 201 
may employ conventional rectifier circuitry 203 and conventional current 
sourcing and regulating circuit 205. Such circuitry may be found in 
previously disclosed documents such as aformentioned U.S. Pat. No. 
4,006,396. A battery charger which employs the present invention utilizes 
a battery type detector 207 and charge control circuitry 209. The battery 
type detector 207 measures the voltage potential generated across 
component 113 of the voltage divider of resistor 210 and electronic 
component 113. Battery type detector 207 determines the battery type from 
the sense input potential and communicates the battery type to control 
circuit 209. Control circuit 209 contains predetermined information about 
the battery type and it will establish the rate and types of charge 
controls to provide an optimum rate of charge for a rechargeable battery 
while not charging a non-rechargeable battery type. 
In the preferred embodiment of the present invention in a battery charger, 
a charge state indicator may operate as described previously. The battery 
terminal voltage is used to determine the battery percentage capacity. 
However, when a battery is being charged the terminal voltage may not be 
monotonic with the percentage charge in the battery. This effect occurs in 
NiCd batteries being rapid charged and has been used in some chargers to 
terminate the rapid charge cycle (this technique is commonly known as 
".DELTA.V charging"). A battery charger may charge one battery type 
differently than another battery type and the terminal voltage vs. 
percentage capacities may be different. Thus, one set of terminal voltages 
vs. percentage charge may be optimal for one battery type but not for 
another. The present invention selects a different set of terminal 
voltages vs. percentage charge for each battery type. 
Referring to FIG. 3, a schematic of one type of detector which may be 
employed as battery type detectors 125 or 207 is shown. The configuration 
shown in FIG. 3 is that of a "window" detector using comparators and 
NOR/AND gates. Alternatively, an analog to digital converter and 
microprocessor may be used to perform the same sort of battery type 
detection. One conventional processor (an MC68HC11A8, available from 
Motorola, Inc.) internally contains an analog to digital converter and may 
be programmed to perform the required comparison. In FIG. 3, a regulated 
voltage is serially voltage divided by resistors 301, 303, 305, 307, 309, 
and 311 to produce N voltage levels which are applied to the positive 
input port of N conventional comparators 313, 315, 317, and 319. The sense 
input signal is applied to the negative input of comparators 313, 315, 
317, and 319. The outputs of the comparators are applied to inputs of AND 
and NOR gates 321, 323, 325, and 327 as shown in order to provide 
detection windows for the battery types. The output signals from battery 
type detectors 125 and 207 are on N output lines. In general, a resistor 
used as electronic component 113 in the battery enables the detection of a 
number of battery types limited primarily by the decision of the detector. 
A battery charger control circuit 209 is shown in more detail in the 
schematic diagram of FIG. 4. A microprocessor 401 (such as an PIC16C55 
available from Microchip, Inc.) is used in the present invention to 
control the charging conditions for the battery based upon the battery 
type detected and applied to microprocessor 401 via detector output line 
403. Upon detection of a particular battery type, microprocessor 401 
recalls form its internal memory the charging characteristics of the 
particular battery type connected to the battery charger 201. The battery 
terminal voltage is sensed by conventional voltage detection techniques 
and input to microprocessor 401 where it is compared with the battery 
terminal voltage charge characteristic curve recalled from storage and the 
appropriate amount of current is allowed to enter the battery terminals as 
determined by microprocessor 401 and current source 205. 
The aforementioned U.S. Pat. No. 4,006,396 discloses a technique of 
determining battery charge rates by detecting a particular battery type. 
Different battery types also require type-specific charge controls to 
realize optimum charge performance. For example, the present invention may 
be employed in the selection of charge control controls such as: voltage 
cutoff (in which the charging is terminated when the battery terminal 
voltage exceeds a selected threshold), time (when the battery charging is 
terminated or reduced to a trickle charge after a selected period of 
time), temperature cut off (in which the fast rate charging is terminated 
when the electrochemical cells exceed a selected temperature), 
temperature-controlled voltage cutoff (in which the selected voltage 
cutoff threshold is selectively temperature compensated for 
electrochemical cell temperature) and .DELTA.v charging (in which a 
selected slope of battery terminal voltage versus time is employed to 
determine the time at which charging is reduced or terminated). These 
charge controls are further shown in Table 3. 
Some types of batteries (for example NiCd cell batteries) are susceptible 
to damage if rapid charging is not carefully controlled. High temperatures 
generated during rapid charging may cause damage to the battery and, in 
extreme situations, may cause the battery to explode. Furthermore, as 
disclosed in U.S. Pat. No. 4,727,306 (showing a dual charge rate battery 
charger having charge rate control), a battery being charged at a rate 
less than its maximum rate but greater than its minimum may also cause 
damage to the battery. Each battery type, then, in the present invention 
has its optimum maximum and minimum charge rates recalled and applied 
during its charging cycle. 
FIG. 5 illustrates the various voltage windows which are generated across 
electronic component 113 (within the battery) when a known regulated 
voltage is applied to a voltage divider including electronic component 
113. 
FIG. 6a is a flowchart employed by the microprocessor of a portable 
radiotelephone in its logic and control function 123 in the preferred 
embodiment of the present invention. This method shows how the 
radiotelephone responds to a determination of a particular battery type 
and sets the appropriate low battery alert thresholds and software turn 
off thresholds for the battery end of life. It is anticipated that each 
different battery type can have an independent set of thresholds. 
Following turn on of the radiotelephone equipment at step 601, the 
detector input is read at step 603. (If an analog to digital converter is 
used in the realization of a battery type detector, step 603 would entail 
the reading of the output value generated by the analog to digital 
converter). A determination that is detected level is greater than one 
volt (as indicated from test 605) results in a test of whether the level 
is between one volt and an incremental voltage (.DELTA.v) over one volt, 
at test 607. If the sense input level exceeds one volt plus .DELTA.v a 
test is made to see if the sense input is between one volt plus .DELTA.v 
and one volt plus 2 .DELTA.v (at test 609). The determination of the sense 
input voltage window continues in a similar manner until the window is 
found. Upon detection of the sense input voltage being within a particular 
window results in the battery threshold and end of life thresholds for the 
particular type of battery detected. This is indicated in steps 611 or 
step 613 of this process. Once the thresholds have been recalled and set, 
the process continues with its normal turn on sequence at 615. 
A unique process occurs if the sense input is detected in the window 
between zero volts and one volt. In one implementation of the preferred 
embodiment a "manual test" subroutine is entered (at 617). This manual 
test subroutine allows servicing personnel to manually energize the 
transceiver functions and is particularly useful when the radiotelephone 
transceiver 103 is placed in an appropriate test power supply and enables 
a service technician to determine problem areas within the radiotelephone 
103. A fail-safe system is also employed to prevent damage to a battery by 
deep discharge if the sense contact 109 is broken or misaligned. The 
radiotelephone transceiver 103 assumes low battery alert and turn of 
default values so chosen that no damage will occur to any of the various 
battery types used in the system. 
A similar method of detection is used to set the transmitter power step 
amount (FIG. 6b) to establish the battery terminal voltage versus level of 
charge characteristics stored for particular battery types (see FIG. 6c). 
Likewise, the battery load change hysteresis time constant and expected 
voltage step for each particular battery type (see FIG. 6d) may be 
selected. A portable radiotelephone transceiver 103 may utilize one or 
more of these methods simultaneously in order to establish the operating 
characteristics of the portable radiotelephone transceiver. 
The general shape of the battery terminal voltage versus battery charge 
level characteristics are shown in the graph of FIG. 7. Several battery 
types are represented in the three curves shown. 
The method employed by microprocessor 401 of a battery charger employing 
the present invention is shown in the flowchart of FIG. 8. Upon 
determining that a battery is present at step 803, the detector output is 
read and the battery type is determined at step 805. The optimum battery 
charge rate is determined from the memory of microprocessor 401 from the 
look-up table, at step 807. The look-up table in the memory of 
microprocessor 401 is further searched to find the charge controls for the 
particular battery type determined at step 805, in step 809. In the 
preferred embodiment, the charge control parameters and values used in the 
battery charging process are shown in Table 3. The battery is then charged 
at the rate determined from the charge rate look-up table and with the 
controls also determined from the control look-up table, at step 811. 
Therefore, a battery type detector has been shown and described. Different 
battery types exhibit different discharging and charging characteristics. 
To optimize battery use and lifetime in battery powered equipment, 
operating characteristics of the battery powered equipment are modified in 
accordance with the detected battery type. Likewise, to optimize battery 
charging operations, charge control parameters of battery chargers are 
modified in accordance with a detected battery type. While a particular 
embodiment of the invention has been shown and described, it is to be 
understood that the invention is not to be taken as limited to the 
specific embodiment herein and that changes and modifications may be made 
without departing from the true spirit of the invention. It is therefore 
contemplated to cover the present invention, and any and all such changes 
and modifications, by the appended claims. 
TABLE 2 
______________________________________ 
BATTERY OPERATED EQUIPMENT AMETERS 
DE- TYPE TYPE TYPE TYPE 
FAULT A B C N 
______________________________________ 
Low Bat Warning 
5.80 5.75 5.65 5.60 5.80 
Threshold 
Receive Mode 
Low Bat Turn Off 
5.20 5.20 5.20 5.20 5.10 
Threshold 
Receive Mode 
Low Bat Warning 
5.50 5.50 5.40 5.30 5.35 
Threshold 
Transmit Mode 
Low Bat Turn Off 
5.20 5.20 5.20 5.10 5.10 
Threshold 
Transmit Mode 
Low Battery 0.40 0.40 0.32 0.20 0.25 
Threshold 
Hysteresis Constant 
Charge State 
Parameter(s) 
High 6.05 6.05 6.55 5.85 5.90 
Low 5.65 5.65 6.05 5.35 5.50 
Max Transmitter 
0 dB -3 -1 0 0 
Power Output 
-3 -4 -3 -2 0 
Parameter(s) 
-6 -6 -5 -4 0 
TX Hysteresis 
0.1 0.08 0.15 0.20 0.10 
Voltage 
______________________________________ 
TABLE 3 
______________________________________ 
BATTERY CHARGER CHARGE CONTROLS 
AMETERS 
DE- 
FAULT TYPE A TYPE B TYPE C TYPE N 
______________________________________ 
High 0 mA 400 mA 60 mA 700 mA 2000 mA 
Change 
Rate 
(Current 
Level) 
Low 0 mA 60 mA 80 mA 10 mA 150 mA 
Charge 
Rate 
Temper- 
40 C. 45 C. 55 C. 45 C. 40 C. 
ature 
Cutoff 
Voltage 
0 V Disabled 7.5 V Disabled 
8.2 V 
Cutoff 
High to 
Low 
Charge 
Rate 
Voltage 
Switch 
Point 0 V Disabled Disabled 
Disabled 
7.9 V 
Timer 0 min Disabled 10 hours 
8 hours 
Disable 
Charge No DV Voltage 
Temp. Temp. 
Method Charge and Cutoff Cutoff Cutoff 
Temp. and and and 
Cutoff Temp. Timer Voltage 
Dual Cutoff Dual Cutoff 
Rate Timer Rate Rate 
Change 
Voltage 
Dual 
Rate 
______________________________________