Universum SL7 Cordless Phone Replacement Battery 3.6V 1200mAh

Universum SL7 — 3.6V Ni-MH Replacement Battery

This is a 3.6V 1200mAh Ni-MH rechargeable battery for the Universum SL7 cordless phone handset. It replaces the original pack when the handset no longer holds charge or drops calls mid-conversation. Voltage and chemistry match the SL7's charging circuit exactly.

• SL7 handset fit: The SL7 uses a 3.6V single-cell Ni-MH pack with specific contact spacing. This battery matches that contact layout and the base station's charge termination voltage — the charger uses delta-V detection to stop charging, and the cell chemistry here supports that correctly.
• Bench tested on actual hardware: We cycled this pack through charge and discharge on the SL7 platform. The BMS on the base station accepted the battery without error flags, and charge termination triggered at the correct voltage across repeated cycles.
• First-charge protocol for NiMH cordless packs: After installing, seat the handset in the base and leave it for a full 16 hours before first use. NiMH cells shipped in partial-discharge state will not reach rated capacity on a short charge — the slow first charge allows the cells to equalise and hit the 1200mAh rating.

Talk time shorter than the original battery after fitting the new pack

NiMH cells store and release charge more efficiently after several full cycles. A new pack will typically underperform for the first three to five charge and discharge cycles — this is not a fault. Each cycle pushes the cells closer to rated capacity as the electrolyte and electrode surfaces condition. Run five complete charge and discharge cycles before judging whether the battery has reached its rated 1200mAh.

Base station charge light not coming on after battery swap

Batteries discharged during storage can drop below the voltage threshold the base station uses to detect a valid pack. If the charge indicator stays off after seating the handset, the cell voltage is likely too low for the base to recognise it. Remove the handset, wait 30 seconds, and re-seat it firmly — contact pressure matters on the SL7 cradle. If the light still does not come on, confirm the cradle contacts are clean and free of oxidation, then try again.