Battery monitor for unobstrusive installation with a battery connector

A device for monitoring the environment of a battery. The device takes the form of a generally flat wafer-like substrate having openings therein for receiving the posts of the battery. The device is arranged so that it is sandwiched between the battery and its connector when the female receptacles of the connector are mated with the posts. Circuitry on the wafer contains a memory for recording information about the battery characteristics. This information can be read from the memory to provide knowledge about battery operating time, number of charge/discharge cycles, number and severity of deep-discharge cycles, total time spent in deep discharge, temperature fluctuations and G-loads applied to the battery. By taking advantage of the existing space between mated battery connectors, no additional mounting hardware or battery modifications are required.

BACKGROUND OF THE INVENTION 
1. Technical Field 
This invention relates to sensors and, more particularly, to a device for 
sensing characteristics of a battery. 
2. Discussion 
In many applications it would be desirable to sense the characteristics of 
a battery. This is especially true with batteries that are used to power 
equipment where it is essential that a reliable source of power is 
consistently maintained. For example, batteries used on many systems by 
the Department of Defense are being replaced with the latest technology 
high-reliability, maintenance-free batteries (HRMFB). While improvements 
in reliability and performance are expected from these new batteries, 
reliability engineers need to understand and quantify the actual gains to 
establish optimum maintenance intervals and number of required spares. 
Basing these decisions on real-life performance data, as opposed to 
educated guesses, will yield significant cost savings by reducing the work 
load on battery maintenance and avoiding having too many or too few spare 
batteries on the shelves. The devices may also provide a means for 
determining whether a failed battery was within warranty limits. 
It is known that the environment to which the battery is exposed can 
shorten or prolong expected life. Factors having the greatest effect on 
battery reliability include operating time, number of charge/discharge 
cycles, number and severity (i.e. magnitude depth) of deep-discharge 
cycles, temperature fluctuations, and G-loads. Sensors are currently 
available to measure and record these parameters, but most of them require 
costly retrofit or redesign of the battery structure to enable the sensor 
to be installed. In most cases it is neither practical nor cost effective 
to hard-wire a sensor inside an aircraft battery. Because of these 
drawbacks, data on large numbers of batteries under real operating 
conditions are difficult to obtain. 
The present invention is directed to solving one or more of these problems. 
SUMMARY OF THE INVENTION 
In accordance with the teachings of the present invention, a device is 
provided for obtaining information about battery characteristics, yet is 
easy to install. The device takes advantage of the existing space between 
the mated battery and its connector and non-intrusively monitors and 
records the battery environment. No additional mounting hardware or 
battery modifications are required. Preferably, the unit is entirely 
self-contained and is capable of recording environmental data onto a 
non-volatile memory. 
In the preferred embodiment, the device takes the form of a generally flat 
wafer-like substrate having first and second openings therein for 
receiving the positive and negative posts of the battery. Circuitry 
carried by the substrate is used to detect characteristics of the battery. 
Conductive means are utilized to make electrical connection between the 
posts and the circuitry. The device is constructed so that it lies 
essentially parallel to the battery surface, with the posts extending 
through the openings in the wafer and making contact with the conductive 
means. 
In use, the device is sandwiched between the surface of the battery and the 
connector when the female receptacles therein are mated with the posts to 
supply power to electrical apparatus during normal operating conditions.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
FIGS. 1 and 2 illustrate the battery sensor wafer device 10 of the present 
invention, a battery 12 and a battery connector 14. A positive battery 
post 16 and a negative battery post 18 extend from a major surface 20 of 
the battery 12. The present invention can be used with a wide variety of 
different battery designs. However, it finds particular utility for use 
with high-reliability, maintenance-free batteries (HRMFB) which are used 
on aircraft such as B-52's. In these applications it is of utmost 
importance that the batteries consistently provide the necessary power for 
the aircraft electronic systems. The present invention has the capability 
of sensing and recording pertinent battery reliability data under actual 
operating conditions. Reliability engineers can use this information to 
analyze different battery designs and to more precisely pinpoint when 
replacement of the battery is needed. 
With additional reference to FIG. 3, the battery sensor device 10 includes 
a thin, generally flat substrate 22. Substrate 22 has two holes 24 and 26 
therein that are aligned with the positive battery post 16 and negative 
battery post 18, respectively. Device 10 is designed so that it can be 
slipped over the battery posts 16 and 18 such that it lies essentially 
flush against the battery end face 20 as shown in FIG. 2. Device 10 is 
sufficiently thin that it does not impede the normal mating connection 
with the connector 14. As seen in FIG. 2, the connector 14 typically 
includes female receptacles 28 and 30 that receive posts 16 and 18, 
respectively. Connector 14 can be a standard ELCON battery connector. 
Contacts 32 and 34 on device 10 make electrical contact with posts 16 and 
18, respectively. In this example, contacts 32 and 34 are shown as 
conductive layers lining the sidewalls of the substrate 22 defining holes 
24 and 26, respectively. Other contact constructions such as bendable 
fingers could, of course, also be used. 
Substrate 22 contains one or more devices for detecting characteristics of 
the battery during operation. Preferably, the present invention utilizes 
the circuitry shown in FIG. 4 for sensing, recording and transmitting 
battery information. The sensors include current sensors 40 for sensing 
the current supplied from the battery 12. Suitable current sensors are 
available from Honeywell utilizing magneto-resistive technology. 
Temperature sensors 42 are employed to sense the ambient temperature to 
which the battery is exposed during use. Suitable temperature sensors 
include thermistors available from Honeywell. Voltage sensors 44 serve to 
sense the voltage supplied by battery 12. The voltage sensors are simple 
resistive dividers, whose voltage is read directly by the signal 
conditioning circuitry. 
A real time clock and random access memory (RAM) 46 are also used in this 
particular embodiment. The real time clock is used to provide suitable 
clock signals for tagging events with the time of their occurrences. The 
functions of the clock and RAM can be provided, for example, by Part No. 
MCC146818 from Motorola. 
The sensors 40, 42, 44 and clock/RAM 46 are fed into suitable signal 
conditioning circuitry 48. Signal conditioning circuitry 48 provides the 
necessary signal conditioning to interface the aforementioned components 
with microprocessor 50. Typically, signal conditioning circuitry 48 
includes analog to digital converters and the like for converting analog 
signals from the sensors to digital data for use with the microprocessor 
50. A commercially available example of suitable signal conditioning 
circuitry is the Tile Array signal conditioning circuitry available from 
Exar as Beta 180. Microprocessor 50, in this example, includes 12 
kilobytes of read only memory (ROM) and is available from Motorola as 
component No. MCC68HC711. A non-volatile memory 52 serves to record and 
permanently store information. For example, microprocessor 50 can be used 
to create tables in memory 52 which record the current levels supplied by 
battery 12 per unit time. In other words, the microprocessor 50 stores 
information generated by the current sensor 40 on a timed basis provided 
by clock 46 and stores it in memory 52. Likewise, temperature and voltage 
data can be stored in memory 52. In this example, non-volatile memory 52 
can be a 16 kilobyte memory provided by Xicor as component No. X28C64H. 
The recorded battery information can be read from memory 52 through an 
output port provided by an RS-232 serial interface translator 54 which is 
available from Harris Semiconductor as ICL232. 
The components making up the battery monitoring circuitry of FIG. 4 can be 
suitably arranged on the substrate 22 so as not to impede the normal 
connector-battery connection. In FIGS. 2 and 3 the circuitry components 
are generally indicated by the reference numeral 56. Components 56 are 
located in pockets 58 in the upper surface 60 of substrate 22. Components 
56 thus do not appreciably extend above the surface 60. Electrical 
connection to the components 56 are made by traces on substrate surface 
60. For example, trace 62 extends from positive battery post contact 32 to 
the pocket 58 and makes electrical connection with an appropriate 
component 56 (e.g., voltage sensor 44). Similarly, trace 64 extends from 
negative battery contact 34 to the voltage sensor to thereby monitor the 
voltage supplied via posts 16, 18 to the electrical equipment during use. 
It will be appreciated that, depending upon the degree of sophistication, 
more than one trace may be required and that the components 56 can be 
placed at various locations on substrate 22. The components, such as 
integrated circuit dies, are connected, for example, by conventional wire 
bonds between the die and the termination of the traces. A glob topcoating 
or other protective measures can be placed over the die, if desired. The 
top and bottom surfaces of the substrate 22 can also be covered with a 
suitable Kapton protective layer (not shown). 
Trace(s) 66 extends from the component serving as a serial interface 
translator to an input/output port 68. Port 68 is suitably located near an 
edge of substrate 22 to receive an external connector, as will appear. A 
suitable power converter (not shown) is also preferably employed to take 
power from the battery post and convert it to levels suitable for powering 
the various components 56 such as microprocessor 50. An auxiliary backup 
battery may also be employed, if desired. 
By way of non-limiting, yet specific examples, substrate 22 is a phenolic, 
nonconductive circuit board which is approximately 0.020 to 0.060 inch 
thick. In order to provide for proper mating with connector 12, the 
thickness of wafer 10 should be less than about 15 percent of the length 
of battery posts 16 and 18. 
In operation, the device 10 is slipped over the battery posts 16 and 18 so 
that they extend through holes 24 and 26, with the substrate 22 lying 
essentially flush against battery end face 20. Connector 14 is then mated, 
in the normal fashion, with posts 16 and 18 to provide power to the 
electrical equipment which is schematically illustrated by box 70 in FIG. 
1. As the battery is used to power equipment 70, the sensors 40, 42 and 44 
continually provide information about the battery characteristics. This 
information can provide, for example, the number of charge/discharge 
cycles, the number and severity of deep-discharge cycles, total time spent 
in deep-discharge, and temperature fluctuations. Shock sensors and other 
similar sensors (not shown) could also be used to detect other operating 
environments such as the G-loads supplied to the battery. Microprocessor 
50 can be suitably programmed to perform the desired data manipulation 
functions via input/output port 68. 
The information stored in memory 52 is easily read from device 10. As shown 
in FIG. 5, a hand-held data collector 72 includes a cord 74 having a 
suitable connector 76 on one end thereof which slides over the edge of 
device 10 to make electrical contact with the traces of input/output port 
68. Data can be read from memory 52 in a known manner so that the stored 
information is transmitted to data collector 72. If desired, the hand-held 
data collector 72 can later transmit this information to a larger computer 
78 for further analysis. Collection of the data can be obtained without 
removing the sensor from the battery. All that is needed is to remove the 
connector 14 and make electrical connection with the input/output port 68. 
Alternatively, the sensor could be hard-wired to computer monitoring 
systems on the vehicle carrying the battery or other read-out devices. 
It should be understood that while this invention has been described in 
connection with a particular example thereof, no limitation is intended 
thereby since obvious modifications will become apparent to those skilled 
in the art after having the benefit of studying the foregoing 
specification, drawings and following claims.