Chemtronics LS 91 & LS 94
TS-4403/U & TS-4403A/U
Battery State of Charge Meter
LiSO2 7 to 9 AH

Brooke Clarke 2002 - 2007

LS 91 Front Panel    LS 94 Front Panel   3/4 View LS 94 w/ BA-5590 Plug


LS 91

LS 94


The manual for the LS 94 is Chemtronics Document No. D110036-00, my copy is dated September 1992.
TM 11-5820-890-20-2 for the SINCGARS radio in chapter 7.3 has operating instructins for the LS-94 to test the BA-5590.


The discharge curves for LiSO2 chemistry are very flat in terms of loaded battery voltage vs. State-Of-Charge.  This means that primary battery testers like the TS-183 or PSM-13 will not be able to tell anything except that the battery has reached its End-Of-Life.
Cables for the BA-5590/U and BA-5598/U have been made and are working.


The case is a very well designed ELMA BV34374-21 modular package. There are 4 major electrical components:

Front Panel with microcontroller printed circuit board

Photo of Front, Photo of Back of Front Panel -

The P2 2x3 pin Molex connector goes to the Electronic Load.
The P3 1x5 Molex connector goes to the power supply.
The back panel has a cutout for some type of D connector. If it was an RS-232 interface then maybe the P4 connector and the missing parts surrounding it are for this interface.
An Intel 87C51 is in the lower right corner running from a 6.000 MHz crystal.
There are a couple of ULN 2803A high current drivers next to the 87C51 on the lower right edge.
An AD650KN (voltage-to-frequency converter) is just to the left of the 87C51.

P1 connects the test socket on the front panel to the PCB with 4 wires:

There are high power components in the upper left corner: Fuse, resistor, diode, 6-pin Omron G6C-2114P-US relay.

The PCB has the markings: LS91MB (Mother Board) Rev 2.3, Assy. 1041006, Chemtronics (C) 1989 1990. SN? 051
On the side is R(reversed)U 94V-0 and the Motorola (circle M) mark, why?
The PCB is a nice double sided design.

There are 4 each Bar Graph LED displays to show the state of charge on the front panel.

Although the Manufacturer Switch on the front panel shows 6 positions (A through F) the mechanical stop has been set to restrict the setting to A, B or C.  There are only 3 manufacturers listed on the lid and only A and B codes are shown.  Why the C position?

F2 (Fuse 2) is not installed.  J1 (a 20 pin machined DIP socket is empty, maybe a test socket?

There are sockets for R13 through R22 with only 3 resistors installed and jumpers in the remaining spaces.  Maybe this State of Charge Meter was designed in a  generic way and customized for specific battery types and manufacturers.

Lambda LVT-40E-144 open frame power supply to drive front panel

Purple & Blue 105 to 250 VAC 47 to 63 Hz input
Yel/Grn Earth

Red +5 Volts +/- 1% 1.0 A @ 60 deg C
Black common
Orange +15 Volts +/- 5% 0.15 A @ 60 deg C
Green Common 2
Yellow -15 Volts +/- 5% 0.01 A @ 60 deg C

Electronic Load on Rear Panel with Massive Heat Sinking

The small PCB is marked LS91EL (Electronic Load) Rev2.3 Chemtronics (C) ASY 1041007 1989 TYPE 1 94V0 S/N 060 the two power devices (Q300 & Q301 have markings of G, D, S (Gate Drain Source).  There is a Motorola (circle M) mark on the PCB, why?

Connector on Front Panel

The connector has "BRUNDY" but no other markings.  It is made of plastic and has 12 holes, but only 4 have sockets isntalled.  The socket inside diameter is about 0.075".  The outside shell diameter is about 0.875" and there are 3 pins to hold the mating connector.  There are 5 slots to key the mating connector.

Brundy is now called Framatome Connectors Inc (FCI) - the cable plug is a UTP61412P (Newark 16F5751) empty connector shell, cable clamp is a UTG14AC (Newark 16F5824), the pins are FCI part number SM14ML1TK6, but Newark only sells 16F5678  in bags of 100 for almost $50 each bag.  A special criping tool is not required. You can use a standard pliers type crimping tool designed for common crimp connectors

Wiring for the BA-5590/U 30 Volt (tests both 15 Volt sections in series) test cable


When the connector that is specific to the battery is connected to the tester and battery and the START TEST button is pressed momentarily, the POWER ON and the TESTING LED are on for about 100 seconds then the TESTING LED turns off and one of the % CAPACITY LEDs turns on.  Note that the highest capacity reading is 70 to 100%.  The military likes to see this LED on when deciding if they are going to recycle a LiSO2 battery.
The Condensed Testing Instructions on the lid say in essence to: The instrument applies a specified load to the battery and monitors the terminal voltage.

The OCV (Open Circuit Voltage) Failure LED lights if:

The CCV (Closed Circuit  Voltage) Failure LED lights if: RETEST when turned on with a % CAPACITY reading The tester makes not only electrical measurements on the battery but also measures the room temperature and uses that data to correct the displayed SOC.

9 Aug. 2004 - When I tried to use the tester right after it was brought indoors from storage, shortly after starting a test both the OCV & CCV LEDs would blink.  After storing the testers indoors they still showed this problem.  But after powering the LS-91 tester overnight it worked properly.  Now will see if leaving the LS-94 on for some time gets it also working.

11 Aug. 2004 - the LS-94 (TS-4403A) still blinks the OCV & CCV lights when I try and test a BA-5590 that checked in at over 70% on the LS-91.  If you know what this blinking light pattern means please let me know.

Other Battery Testers

PSM-13 for a number of dry batteries (BA-4386/PRC-25 included)
TS-183 Dry Battery Tester, does not work on the BA-4386/PRC-25) or on any LiSO2 battery
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