Leica GEB235 CS35 Controller Replacement Battery 11.1V

Leica CS35 Controller — 11.1V Li-ion Replacement Battery (GEB235 / GEB236)

This is an 11.1V, 9600mAh (106.56Wh) Li-ion battery for the Leica CS35 field surveying controller. It replaces OEM part numbers GEB235 and GEB236. The CS35 uses this cell pack to power GPS data collection and on-site measurements during fieldwork.

• CS35 platform fit: The GEB235 and GEB236 share the same voltage rail, connector pinout, and BMS handshake protocol on the CS35 Controller. Both OEM numbers cross to this cell pack without modification.
• Bench tested on actual hardware: We ran this pack through charge and discharge cycles on the CS35 platform. The BMS communicated state-of-charge correctly and no fault flags triggered during high-draw GPS acquisition loads.
• CS35 first-cycle calibration: After installing this pack, run the CS35 down to automatic shutdown, then charge uninterrupted to 100%. This resets the controller's battery learn cycle and clears the inaccurate health warning the CS35 displays after any cell swap.

CS35 shutting down at 20–30% charge shown on screen

This happens because the CS35's fuel gauge IC is still calibrated to the old cell's discharge curve. When the new cell hits the voltage cliff under GPS and display load simultaneously, the pack voltage drops faster than the gauge predicts. The controller reads this as a safe-shutdown threshold and cuts power before the display shows zero. Run two full discharge-to-shutdown cycles followed by uninterrupted full charges — this gives the fuel gauge IC enough data points to remap the curve to the new cell. After the second cycle, the shutdown point typically corrects to below 5% remaining.

CS35 reporting wrong Wh rating in system information after swap

The Wh figure shown in the CS35's system info screen is pulled from EEPROM data stored on the battery's internal circuit board. Replacement cells carry EEPROM values that may differ from the original OEM pack's rated figure, even when actual chemistry and capacity are equivalent. This is a data mismatch between the EEPROM record and what the controller expected — it does not affect charge capacity or field performance. No action is needed, but running the full calibration cycle described above will update the active capacity register the controller uses for charge-level calculations.