Bosch MM588 Cordless Phone Compatible Battery 3.7V 950mAh

Bosch MM588 — 3.7V Li-ion Replacement Battery (4.998.020.274)

This is a 3.7V, 950mAh Li-ion replacement battery for the Bosch MM588 cordless DECT handset. It fits the MM588 directly and matches the OEM part number 4.998.020.274. Install it when the original cell no longer holds enough charge to sustain a call or keep the handset active on the base.

• MM588 handset fit: The MM588 uses a single-cell 3.7V Li-ion pack with a specific connector orientation and BMS handshake. This cell matches that voltage rail and connector, so the handset's charge circuit accepts it without a fault state.
• Bench tested on actual hardware: We cycled this cell through the MM588's charge and discharge circuit. The BMS reported no errors across charge acceptance, cell voltage monitoring, and cutoff thresholds.
• First-charge protocol for the MM588: After fitting this cell, seat the handset in the base and leave it undisturbed for a full 16 hours before the first call. Li-ion cells shipped in storage-state benefit from one full slow charge before regular use — skipping this step often causes users to report short talk time in the first week.

Talk time shorter than expected after fitting the new cell

A freshly shipped Li-ion cell arrives partially discharged — typically between 30% and 50% state of charge. The MM588's charge circuit starts from that partial state, so if the handset is used before a full baseline charge completes, available talk time is low. This is not a fault with the cell. Run one full 16-hour charge cycle from flat, and talk time should reach rated capacity. If it does not improve after two full cycles, check that the handset contacts are clean and seating firmly in the base.

Base station showing no charge or error light after battery swap

When a replacement Li-ion cell arrives at a low storage voltage, some DECT base stations refuse to initiate charging — the charge controller sees a voltage below its acceptance threshold and flags it as a fault rather than starting a trickle charge. Remove the handset from the base, wait 10 seconds, then reseat it firmly so both charge contacts make full connection. If the error persists, check the base contacts for oxidation and clean with a dry cloth. The cell voltage should recover to normal charge-accept range within the first completed cycle.