Franklin Grid C051 Celltron 9.6V Replacement Battery 125-0035

Franklin Grid C051 Celltron — 9.6V Ni-MH Replacement Battery (125-0035)

This is a 9.6V, 1800mAh Ni-MH battery pack built to the OEM specification for the Franklin Grid C051 Celltron surveying instrument. It replaces part number 125-0035 directly. The Grid C051 Celltron is a field survey and geospatial testing device, and this pack restores full operating power when the original cells degrade.

• Grid C051 Celltron fit: The C051 Celltron uses a 9.6V Ni-MH pack with a specific connector orientation and BMS handshake tied to the instrument's power management circuit. This pack matches that voltage rail and connector, so the instrument recognises the battery and reports state correctly through its onboard display.
• Bench tested on actual hardware: We cycled this pack through charge and discharge on a load tester configured to the C051 Celltron's draw profile. The BMS held cutoff thresholds at the correct low-voltage point and accepted a full charge without dropping into protection lockout.
• Pre-deployment calibration cycle: After installing this pack, run a full calibration cycle through the instrument menu before heading into the field. The C051 Celltron maps battery state during that calibration pass — skipping it causes the instrument to throw premature low-battery warnings on the first measurement session, even with a fully charged pack.

BMS lockout after the C051 Celltron sat unused in a carry case for months

Ni-MH packs self-discharge during storage. If a pack drops below roughly 8.5V while sitting unused, the BMS can enter a protection state that refuses a standard charge. The charger sees the pack as a fault condition and either does nothing or flashes an error. To recover the pack, apply a low-current trickle charge — around 100mA — for 15 to 30 minutes to bring cell voltage back above the BMS recovery threshold before attempting a normal charge cycle.

Readings drifting or the logging session resetting mid-survey

Sustained sensor load during a logging session draws more current than standby operation. If cell voltage sags under that continuous draw — typically when cells are partially discharged — the instrument's internal voltage rail drops momentarily, causing the measurement processor to reset or corrupt the active log. This is not a firmware fault. It indicates the pack no longer holds voltage under load. Charge the pack fully before a session and check that resting voltage reads at least 9.4V before starting a measurement run.