About this replacement
Leica CS20 / GS18 Series — 11.1V Li-ion Replacement Battery (GEB331 / GEB333 / GEB334)
This 11.1V, 6900mAh lithium-ion battery replaces the Leica GEB331, GEB333, GEB334, GEB363, and GEB364 cells used in the CS20 field controller, CS20 Controller, and GS18 GNSS antenna units. It slots into the same battery bay and connects through the same BMS handshake as the original pack. Voltage and capacity match the OEM specification exactly.
- CS20 and GS18 platform fit: These instruments share a common battery form factor, connector pinout, and BMS communication protocol across the CS20 controller family and GS18 antenna receivers — one pack covers the full platform without adapter modifications.
- Bench tested on actual hardware: We cycled this pack through the CS20's full startup sequence and sustained GNSS tracking load. The BMS held stable communication with the instrument throughout, with no mid-session cutoff events observed under continuous measurement load.
- Post-install calibration cycle: After fitting this pack, run a full calibration cycle through the CS20 instrument menu before field deployment. The CS20 maps battery state during that sequence — skipping it causes premature low-battery warnings to appear during your first measurement session in the field.
BMS lockout after the CS20 sat unused in a carry case for months
Lithium-ion cells in survey instruments self-discharge slowly during storage. If a pack sits long enough, cell voltage drops below the BMS recovery threshold — typically around 2.5V per cell — and the protection circuit latches off to prevent damage. At that point the CS20 shows no charge activity and will not power on, even when placed on the charger. The fix is to apply a slow pre-charge using a compatible charger that supports recovery mode, which nudges cell voltage above the 3.0V threshold needed for the BMS to re-enable normal charge current.
CS20 shuts down mid-measurement with no prior low-battery warning
This usually points to a voltage sag event, not a depleted pack. When the CS20 powers its radio modem and GNSS receiver simultaneously — particularly during a data upload or base station sync — instantaneous current draw spikes sharply. If the pack's internal resistance has risen with age, terminal voltage dips below the BMS cutoff threshold for a fraction of a second, which the instrument reads as a fault and shuts down. A fresh pack with lower internal resistance handles the combined draw without the voltage drop. Confirm the new pack is delivering stable voltage above 10.5V under load using the instrument's diagnostics menu before heading to site.