GP55AAABMU 3.6V Ni-MH Cordless Phone Replacement Battery 800mAh

GP GP55AAABMU — 3.6V Ni-MH Replacement Battery for Cordless Phones

This is a 3.6V, 800mAh Ni-MH replacement battery built to the GP55AAABMU specification. It fits cordless DECT handsets that use this part number. If your handset no longer holds a charge or drops calls mid-conversation, this battery restores the handset to working condition without replacing the whole phone.

• GP55AAABMU compatibility: Cordless phones using this part number share a common 3.6V three-cell NiMH pack format with the same connector orientation and physical footprint. The voltage rail matches what the handset's charging circuit expects — no wiring changes needed.
• Bench tested on actual hardware: We ran this pack through charge and discharge cycles on a NiMH-compatible test rig. The BMS accepted charge from a standard DECT base station without triggering fault states, and cell balance remained consistent across cycles.
• First-charge protocol for NiMH cordless packs: After installing, seat the handset in its base and leave it for a full 16 hours before first use. NiMH cells in cordless phones require a slow initial charge to reach rated capacity — skipping this step is the most common reason a new battery underperforms from day one.

Base station showing no charge light after fitting a new NiMH pack

A NiMH battery that has been in storage can drop to a voltage low enough that the base station's charging circuit won't accept it. Most DECT bases use a delta-V detection method — they expect the pack voltage to rise at a minimum rate. A deeply discharged cell can sit below the base's acceptance threshold entirely. If the charge indicator stays off or shows an error light, remove the handset, wait 30 seconds, and reseat it firmly. Some bases need a brief trickle current before they recognise the pack — this usually resolves within the first 10 minutes of contact.

Handset not pairing with base after battery replacement

Some DECT phones lose their pairing data when the battery is fully removed, because the handset stores pairing keys in volatile memory backed by the pack. When the new battery goes in, the handset boots with no stored base ID and won't register. To fix this, run a fresh registration: hold the handset's paging or find button on the base for 5–10 seconds until the base beeps, then follow the phone's pairing sequence in the menu — consult your handset manual for the exact keypress, as it varies by manufacturer.