About this replacement
GeoMax Zenith 35 GPS GNSS — 10.8V Li-ion Replacement Battery (827967 / ZBA601)
This 10.8V, 3400mAh Li-ion battery replaces the OEM pack in the GeoMax Zenith 35 GPS GNSS surveying receiver. It fits the Zenith 35, Zenith35, and Zenith35 GNSS variants. Voltage and cell count match the original specification exactly.
- Zenith 35 platform fit: All three Zenith35 variants share the same battery bay geometry, connector pinout, and BMS handshake protocol. One pack covers the full line without modification.
- Bench tested on actual hardware: We ran this pack through charge and discharge cycles on the Zenith 35 platform. The BMS communicated state-of-charge correctly to the receiver's battery indicator, and no cutoff events occurred under sustained GNSS tracking load.
- First-field calibration cycle: After installing a new pack, run a full calibration cycle through the Zenith 35 instrument menu before heading to site. The receiver maps battery state during calibration — skip this step and you will see premature low-battery warnings on your first survey session even with a full charge.
BMS cutoff when the Zenith 35 initialises its satellite tracking module
When the Zenith 35 powers on, the GNSS tracking module draws a short but sharp current spike as it initialises antenna bias voltage and begins acquiring satellites. A weak or deeply discharged cell cannot meet that instantaneous demand, so the BMS trips as a protection measure before the receiver reaches its operating screen. This pack's cells are rated to handle that inrush without triggering a cutoff. If you are seeing shutdowns at the splash screen, charge the pack to at least 11.5V on the terminal pins before reinserting.
Zenith 35 showing erratic battery percentage after the pack sat unused for months
Li-ion cells self-discharge over storage. If the pack drops below the BMS recovery threshold — typically around 2.5V per cell — the BMS enters sleep mode and the receiver either refuses to power on or shows a wildly incorrect state-of-charge reading at reboot. Place the pack on charge immediately and leave it for a full cycle without interruption. Most BMS units recover within the first charge cycle; if the indicator still reads incorrectly after one full charge, run a second charge cycle before assuming the pack is faulty.