Bosch MS687 Cordless Phone Replacement Battery 3.6V 750mAh

Bosch MS687 — 3.6V Ni-MH Replacement Battery (145306002110)

This is a 3.6V, 750mAh Ni-MH battery for the Bosch MS687 cordless DECT handset. It slots into the handset battery compartment and restores full talk and standby operation. Capacity matches the original specification — 750mAh at 2.7Wh.

• MS687 handset fit: The MS687 runs on a slim single-cell Ni-MH pack at 3.6V. The base station's charging circuit is tuned to that voltage and cell chemistry — swapping to Li-ion or a different voltage will trip the charge error light or fail to charge entirely. This pack keeps the original voltage rail and chemistry intact.
• Bench tested on actual hardware: We cycled this pack through charge and discharge on a DECT phone test rig. The BMS accepted charge from the base station without flagging an error, and the handset registered a full charge indicator after the conditioning cycle completed.
• First-charge conditioning for Ni-MH: After fitting, seat the handset in the base and leave it for a full 16 hours before first use. Ni-MH cells in cordless phones ship partially discharged — a slow initial charge lets the cells reach rated capacity and sets the baseline for accurate charge-level readings.

Range dropping on the MS687 after a battery swap

DECT transmit power on the MS687 handset draws a short, sharp current spike each time the radio fires. A Ni-MH pack that hasn't been conditioned yet has higher internal resistance, which causes voltage to sag under that RF load. The handset compensates by reducing transmit power, and you lose range — sometimes significantly in the first few days. Running three to five full charge-discharge cycles brings internal resistance down and stabilises the voltage under RF load. After conditioning, transmit power returns to normal and range recovers.

Base station showing a charge error or no-charge light on a new pack

New Ni-MH packs often arrive from storage with a resting voltage below the threshold the MS687 base station expects before it starts its charge cycle. When the base reads that low voltage, it flags an error instead of charging. The fix is to leave the handset seated in the base undisturbed for up to 30 minutes — the trickle current from the base will nudge the pack voltage above the acceptance threshold, at which point the base switches to normal charging. If the error light clears and the charge indicator appears, the pack is charging correctly. Target resting voltage after a full charge cycle is approximately 4.2V across the three cells.