Ascom R1D Replacement Battery BKB201010/1 3.7V 650mAh Li-ion

Ascom R1D / D41 / D43 Series — 3.7V Li-ion Replacement Battery (BKB201010/1)

This is a 3.7V, 650mAh lithium-ion replacement battery for the Ascom R1D, D41, 9D41, and D43 cordless DECT handsets. It slots into the handset battery compartment and restores power to the wireless unit. OEM part numbers BKB201010/1, FA01302005, and FA83601195 all cross-reference to this same cell configuration.

• R1D, D41, 9D41, and D43 compatibility: These handsets share the same battery footprint, connector orientation, and 3.7V supply rail. The BMS handshake is identical across the range, so one cell fits all four models without modification.
• Bench tested on actual hardware: We ran this battery through full charge and discharge cycles on the D41 platform. The BMS held voltage within spec under both standby and active RF transmission loads, with no cutoff events during normal handset operation.
• First charge on DECT handsets: After fitting this battery, seat the handset in the base station and leave it on charge for a full 16 hours before first use. Li-ion cells shipped in storage state need a complete slow charge to reach rated capacity — skipping this step will leave the first few cycles well below the 650mAh rating.

Talk time shorter than expected after fitting the new battery

Li-ion cells arrive partially discharged after storage — typically between 30–50% state of charge. One charge cycle from that point does not bring the cell to full rated capacity. Most handsets in this series need three to five full charge-discharge cycles before the battery stabilises at its rated 650mAh. If talk time is still noticeably short after five cycles, check that the handset is making clean contact with the base station charging pins.

Base station charge light not activating with new battery installed

When a Li-ion cell arrives deep in storage discharge, its resting voltage can fall below the threshold the base station uses to confirm a valid battery is present. The base then withholds charge current rather than risk a fault condition. Remove the handset, wait 30 seconds, and reseat it firmly — this resets the charge detection cycle on most Ascom bases. If the charge light still does not activate, measure the battery terminals with a multimeter; a reading below 3.0V means the cell needs a brief pre-charge pulse before the base will accept it.