Aastra JB950 Cordless Phone Replacement Battery 3.6V 600mAh

Aastra JB950 — 3.6V Ni-MH Replacement Battery

This 3.6V 600mAh Ni-MH battery replaces the original rechargeable cell in the Aastra JB950 cordless phone handset. It restores talk time and standby operation when the factory battery no longer holds charge. Dimensions are 42.45 × 29.77 × 14.37mm — verify fit against your existing cell before installing.

• JB950 handset compatibility: The JB950 runs a 3.6V single-cell Ni-MH pack. The base station's charging circuit is calibrated for Ni-MH chemistry — it uses a trickle-charge termination that won't work correctly with Li-ion cells of the same voltage, so chemistry match matters here.
• Bench tested on actual hardware: We cycled this pack through charge and discharge on the bench. The BMS accepted the NiMH charge profile without error flags, and voltage held stable across the RF transmit bursts the DECT radio produces during active calls.
• First charge on the JB950: After installing, seat the handset in the base and leave it for a full 16 hours before making calls. Ni-MH cells shipped at partial charge need a slow, complete first cycle to reach rated capacity — skipping this shortens the usable capacity you get from the replacement.

Base station showing no charge light after swapping the battery

Ni-MH cells lose voltage during storage — if this pack sat in a warehouse, it may arrive below the threshold the JB950 base station needs to recognise a valid battery and begin charging. The base looks for a minimum voltage before it switches the charging circuit on. If the charge indicator stays off, place the handset in the base and wait up to 30 minutes — the trickle stage will slowly bring the cell up to the acceptance threshold. If the light comes on after that window, the cycle is working normally.

Talk time shorter than expected after replacement

Ni-MH cells don't hit rated capacity on the first charge cycle — this is normal chemistry behaviour, not a faulty battery. Rated capacity is typically reached after three to five full charge and discharge cycles. Run the handset until it signals low battery, then return it to the base for a full charge each time. By cycle four or five, talk time should reach the level the 600mAh rating reflects.