Siemens Gigaset SL3501 Replacement Battery 3.6V 500mAh

Siemens Gigaset SL3501 — 3.6V Ni-MH Replacement Battery (V30145-K1310-X127)

This 3.6V, 500mAh Ni-MH pack replaces the original battery in the Siemens Gigaset SL3501 cordless handset. It also fits the Gigaset SL30, Gigaset 4000 micro, Gigaset 4000s micro, and 16 additional Gigaset models. All specs match the OEM unit — same voltage, same form factor, same connector orientation.

• Gigaset SL and 4000 series compatibility: These handsets share a common 3.6V NiMH cell format and identical cradle-contact pinout across the SL and 4000 micro lines. One battery cell block fits all of them without modification to the housing or contacts.
• Bench tested on actual hardware: We cycled this pack through the Gigaset base station charging circuit and confirmed the BMS accepted charge from the first seating. Charge termination triggered correctly at full capacity without overrun.
• First-charge protocol for NiMH cordless packs: After installing, seat the handset in the base cradle and leave it for a full 16 hours before the first call. NiMH cells in cordless handsets reach rated capacity only after a slow initial charge — rushing this step cuts usable capacity on every subsequent cycle.

Talk time shorter than original battery after replacement

NiMH cordless phone batteries do not deliver full rated capacity on cycle one. The cells need three to five full charge-and-use cycles before the electrodes stabilise and capacity reaches the rated 500mAh. If talk time feels short after the first day, that is expected — not a fault. Run the handset down until the low-battery alert sounds, then return it to the base for a full charge, and repeat for at least three cycles.

Base station not charging after battery swap

Gigaset base stations check incoming voltage before committing to a charge cycle. A NiMH pack that has sat in storage can drop below the threshold the base expects — typically under 3.0V — and the base reads it as a fault rather than a flat battery. To recover it, reseat the handset firmly so both cradle contacts are flush, then leave it undisturbed for 30 minutes. The base will trickle charge to 3.0V and then switch to normal charge mode automatically.