Crofone ADP4000 Cordless Phone Replacement Battery 3.6V 550mAh

Crofone ADP4000 — 3.6V Ni-MH Replacement Battery

This is a 3.6V, 550mAh Ni-MH battery for the Crofone ADP4000 cordless handset. It replaces the original cell pack directly, restoring power to the handset without any modification. If your handset no longer holds a charge or dies mid-call, this is the part that fixes it.

• ADP4000 handset compatibility: The ADP4000 runs on a 3.6V NiMH cell pack at this exact form factor — 47.52 × 34.18 × 6.58mm. The connector orientation and cell arrangement match the original, so the pack seats correctly in the handset battery bay without forcing or trimming.
• Bench tested on actual hardware: We cycled this pack through charge and discharge on NiMH-compatible test equipment. The cells accepted charge current correctly, BMS protection tripped at expected low-voltage cutoff, and capacity stabilised by the third full cycle.
• First charge on NiMH cordless handsets: After installing this battery, place the handset in the base and leave it for a full 16 hours before first use. NiMH cells in cordless phones do not reach rated capacity on the first charge — the slow first cycle conditions the cells and prevents early capacity loss.

Base station showing charging error after fitting a new NiMH pack

A new NiMH battery shipped from storage can sit at 1.0V per cell or lower. Some ADP4000 base stations check voltage before starting the charge cycle and refuse to charge a pack that reads below their acceptance threshold. This is not a fault with the battery or the base — it is a voltage floor check. To recover the pack, place the handset in the base and leave it undisturbed for 30 minutes. Most bases will trickle-charge a low pack until it crosses the threshold, typically around 3.0V total, then switch to normal charge mode.

Talk time shorter than expected after the first few charges

NiMH cells need three to five full charge-discharge cycles before they reach rated capacity. If talk time feels short immediately after installation, the cells are not yet conditioned — this is normal behaviour, not a defective battery. Run the handset until the low-battery indicator triggers, then return it to the base for a full charge. Repeat this three times and capacity will stabilise at or close to the rated 550mAh.