Topcon BT-32Q CTS-3000 Survey Replacement Battery 7.2V 2500mAh

Topcon CTS-3000 / GPT Series — 7.2V Ni-MH Replacement Battery (BT-32Q)

This is a 7.2V, 2500mAh Ni-MH replacement for the Topcon BT-32Q battery pack. It fits the CTS-3000 total station and the GPT-1000, GPT-1003, and GPT-2000 series instruments, along with fourteen additional compatible models. Voltage and capacity match the original Topcon specification exactly.

• CTS-3000 and GPT platform compatibility: These Topcon total stations share the same battery bay geometry, 7.2V rail, and BMS handshake protocol. The BT-32Q connector keys into the instrument contact block without modification, and the pack registers normally on the battery status screen.
• Bench tested on actual hardware: We ran this pack through charge and discharge cycles on a CTS-3000 body. The BMS held stable across EDM firing sequences and angular encoder reads — both of which pull current simultaneously and stress the pack harder than standby draw.
• First deployment calibration: After installing a new pack, run a full calibration cycle through the instrument menu before heading into the field. The CTS-3000 maps battery state during calibration, and skipping this step causes the low-battery indicator to trigger prematurely on your first measurement session.

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

Ni-MH cells self-discharge at roughly 1–2% per day at room temperature. A pack stored for several months can drop below the BMS recovery threshold — typically around 5.4V for a 7.2V Ni-MH pack — and the protection circuit locks out to prevent cell reversal. The instrument will not power on and the charger may show no activity. Place the pack on the charger and leave it for a full 12-hour cycle; most BMS circuits re-initialise once the charger trickles enough current to bring cell voltage back above the recovery floor.

Instrument shuts down mid-measurement with no prior low-battery warning

This happens when the EDM fires and the angular encoder reads at the same time — combined current draw causes a brief voltage sag that the BMS reads as an under-voltage fault. An aged or partially depleted pack sags harder under simultaneous load than the battery indicator anticipates. The instrument cuts power before any warning appears on screen. Charge the pack fully, confirm the resting voltage sits at or above 8.4V off the charger, then retest — if sag shutdowns continue on a full charge, the cells have lost capacity and the pack needs replacing.