Swisscom TOP S317 Compatible Battery 3.7V 1300mAh

Swisscom TOP S317 — 3.7V Li-ion Replacement Battery

This is a 3.7V, 1300mAh (4.81Wh) lithium-ion battery for the Swisscom TOP S317 cordless DECT handset. It replaces the original cell when the handset stops holding a charge or drops off calls shortly after leaving the base. Dimensions are 53.60 × 36.95 × 7.95mm — confirm these match your existing cell before ordering.

• TOP S317 handset fit: The S317 runs a single-cell 3.7V Li-ion pack at a fixed connector orientation. This cell matches that voltage rail and physical footprint, so the handset's charge controller sees the correct input from the base station.
• Bench tested on actual hardware: We cycled this cell through charge and discharge on a Li-ion test rig. The protection circuit triggered correctly at low-voltage cutoff and the cell accepted a full charge without thermal deviation.
• First charge after installation: Li-ion cells shipped in storage state may read low voltage. Place the handset in the base immediately after installing the battery and leave it for a full charge cycle before first use — this lets the handset's charge circuit initialise to the cell's actual state of charge.

Base station charge light not responding after swapping the battery

Li-ion cells lose voltage during storage. If the cell voltage drops far enough, the S317 base station's charge circuit may not recognise it as a valid battery and will show no charge activity or an error light. The fix is to check whether the handset contacts and base cradle contacts are clean — oxidation on either side breaks the circuit. If contacts are clean and the base still shows no activity, leave the handset seated for 30 minutes; most base stations will begin a trickle charge once the cell climbs above roughly 3.0V.

Handset loses DECT pairing after battery replacement

Removing the battery from a DECT handset cuts power to the pairing memory on some S317 units. When power is fully lost, the handset may forget its registered base station and show "searching" or refuse incoming calls. To fix this, re-register the handset from the base station's menu — on most Swisscom DECT bases this is under Settings → Register Handset. You will need the base PIN, which defaults to 0000 on unmodified units.