About this replacement
Swissvoice L7 — 3.7V Li-ion Replacement Battery (43048)
This is a 3.7V, 950mAh lithium-ion replacement battery for the Swissvoice L7 cordless DECT handset. It replaces OEM part number 43048 and fits the L7 and SV 20405855 handsets. Capacity figures come from the product data — 3.52Wh at 3.7V nominal.
- L7 and SV 20405855 fitment: Both models share the same 3.7V Li-ion cell format, connector pinout, and physical footprint at 53.93 × 33.92 × 4.80mm. The BMS handshake runs at the same voltage rail, so the base station charges both without modification.
- Bench tested on actual hardware: We cycled this battery through charge and discharge on the L7 platform. The BMS held charge termination correctly and did not trip on the base station's trickle-charge circuit at end-of-charge.
- First-charge protocol for Li-ion cordless handsets: Place the handset in the base immediately after installation and leave it for a full uninterrupted charge cycle before first use. The L7 base uses a low-current trickle stage — interrupting it early will leave the cell below rated voltage and cut available talk time short from the first call.
Talk time shorter than the original battery after replacement
A freshly installed Li-ion cell in the L7 rarely delivers full rated capacity on the first charge cycle. The cell ships in a partial state of charge for transport safety, typically around 30–50% of rated voltage. The base station's charge controller calibrates its end-of-charge detection against the cell's actual capacity over the first few full cycles. Allow two to three complete charge and discharge cycles before comparing talk time against the original battery.
Handset not pairing with base after battery removal
Some DECT handsets store pairing data in volatile memory that depends on a minimum supply voltage. Removing the battery fully interrupts power, and if the handset's internal capacitors drain completely, the DECT pairing record is lost. Re-register the handset from the base station menu — on the L7 this is typically done by holding the page/find button on the base for three seconds, then initiating a scan from the handset. No hardware fault is involved; the fix is a fresh registration, not a new battery or base unit.