Mitel 5610 Cordless Phone Compatible Battery 3.7V 1200mAh

Mitel 5610 — 3.7V Li-ion Replacement Battery (51015404)

This 3.7V 1200mAh Li-ion battery replaces the OEM pack in the Mitel 5610 cordless handset. It fits the 5610 DECT phone used in enterprise phone systems. Voltage and cell chemistry match the original specification exactly.

• Mitel 5610 fitment: The 5610 handset uses a slim single-cell Li-ion pack at 3.7V nominal. This battery matches that voltage rail, connector pinout, and physical footprint — 53.20 × 34.00 × 5.70mm — so it seats correctly without modification.
• Bench tested on actual hardware: We cycled this battery through charge and discharge on the 5610 platform. The BMS responded correctly to the base station charge signal, accepted a full charge without fault, and held voltage within spec across the discharge curve.
• First charge on the Mitel 5610 base: After installing this battery, seat the handset in the 5610 base station and leave it for a full 16 hours before first use. Li-ion cells shipped from storage may sit at a reduced state of charge, and a complete first cycle brings the pack to rated capacity.

Talk time shorter than original battery after replacement

A freshly installed Li-ion pack often delivers noticeably less talk time on the first few cycles. This happens because the cells leave storage at a partial charge state and the BMS has not yet calibrated its capacity tracking to the new pack. Run two to three full charge and discharge cycles through the 5610 base before judging capacity. After conditioning, the pack should reach its rated 1200mAh and match or exceed the worn original.

Mitel 5610 base station shows no charge light after battery swap

If the base station shows no charge indicator after installing a replacement pack, the battery voltage has likely dropped below the threshold the charger circuit expects before initiating a charge cycle. Remove the handset, wait 10 seconds, and reseat it firmly — the charge contacts on the 5610 handset base are spring-loaded and a poor connection will prevent the charge circuit from activating. If the issue persists, check the battery terminal voltage directly; it should read above 3.0V for the base to accept it. A pack reading below 3.0V may need a brief external top-up to cross the acceptance threshold.