Topcon BT-24Q GTS-300D Replacement Battery 7.2V 2700mAh

Topcon GTS-300D Series — 7.2V Ni-MH Replacement Battery (BT-24Q)

This is a 7.2V 2700mAh Ni-MH replacement for the Topcon BT-24Q battery pack. It fits the GTS-300D, GTS-301D, GTS-302D, GTS-303D, and compatible models in the GTS-300 series total station lineup. These are precision survey instruments used for angle measurement, positioning, and construction layout work in the field.

• GTS-300 series compatibility: The GTS-300D through GTS-303D share the same 7.2V battery bay, connector pinout, and charge-management handshake. One pack fits all models in the series without adapter or modification.
• Bench tested on actual hardware: We ran this pack through charge and discharge cycles on a GTS-300 series unit. The BMS held stable across sustained EDM and angle-logging draws, and the instrument accepted the pack without throwing a battery fault code.
• Post-install calibration cycle: After fitting this pack, run a full calibration sequence through the instrument's menu before going to site. The GTS-300 series maps battery state during calibration — skip this and the instrument will flag premature low-battery warnings on the first measurement session, even with a full charge.

BMS lockout after the GTS-300D 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 three to six months without a top-up can drop below the BMS recovery threshold — typically around 5.4V for a 7.2V pack. When this happens, the charger may show no activity and the instrument may not power on at all. Place the pack on a Ni-MH compatible charger that supports recovery or trickle-charge mode and allow it to accept a slow charge before attempting a full cycle.

GTS-300D shuts off mid-session with no low-battery warning

This happens when sustained EDM or motorised measurement draws pull voltage below the BMS cutoff threshold before the display indicator catches up. The indicator reads cell voltage at rest, not under load — so it shows 50% and the unit cuts out seconds later. Ni-MH cells in older packs also show a flat discharge curve that compresses the warning window. Charge the pack fully, run the calibration cycle, and check that resting voltage after a full charge reaches at least 8.4V before deploying to site.