KPN Miami 50 Cordless Phone Replacement Battery 3.6V 600mAh

KPN Miami 50 — 3.6V Ni-MH Replacement Battery

This is a 3.6V, 600mAh Ni-MH replacement battery for the KPN Miami 50 cordless DECT handset. It slots directly into the handset battery compartment and restores power to the phone when the original cell can no longer hold a charge. Dimensions are 30.30 × 42.60 × 14.30mm — check these against your existing pack before ordering.

• KPN Miami 50 handset fit: The Miami 50 runs a single-cell Ni-MH pack at 3.6V to power both the DECT radio module and the handset display. Any deviation in voltage or cell count causes the base station to reject the charge cycle or show a fault light — this pack matches the original cell configuration exactly.
• Bench tested on actual hardware: We cycled this pack through charge and discharge on a Ni-MH test rig. The cell accepted a full charge without thermal event, and voltage held within spec across the discharge curve at low-current DECT standby draw.
• First-charge protocol for Ni-MH handsets: After installing, place the handset in the base for a continuous 16-hour charge before first use. Ni-MH cordless batteries ship in a partially discharged state — skipping this slow initial charge leaves the cell short of rated capacity from the start.

Base station showing a charging error after fitting a new Ni-MH pack

KPN DECT bases use a delta-V detection circuit to confirm a Ni-MH pack is present and accepting charge. A new cell shipped from storage often sits below 3.0V, which is outside the window the base expects at contact. The base interprets this as a fault rather than a discharged cell. To recover, remove the battery, connect it to a standalone Ni-MH charger at a slow rate (around 60mA) until it reads above 3.3V, then reseat it in the handset.

Talk time shorter than the original battery after replacement

A fresh Ni-MH cell does not deliver full rated capacity on the first cycle — this is normal chemistry behaviour, not a defective battery. The cell needs three to five full charge-discharge cycles before it reaches the 600mAh rating. Each cycle, usable capacity steps up noticeably. Run the handset down to the low-battery warning, then return it to the base for a full charge — repeat this at least three times before judging talk time.