About this replacement
SpectraLink S35 / S37 DECT Handset — 3.7V Li-ion Replacement Battery (84743432)
This 3.7V, 1200mAh lithium-ion battery replaces OEM part 84743432 in the SpectraLink S35 and S37 DECT handsets. It fits both variants of the S35 platform that share the same battery bay and connector. Voltage and capacity match the original specification exactly.
- S35 and S37 platform fit: Both models run the same 3.7V Li-ion cell format with identical connector orientation and BMS pin-out. One replacement battery covers the full S35 series handset range without modification.
- Bench tested on actual hardware: We ran this cell through charge and discharge cycles on an S35 handset. The BMS accepted the pack without fault codes, voltage held steady under DECT RF transmit load, and the base station reported a normal charge state throughout.
- First charge on the S35 base station: After fitting this battery, seat the handset in its charging cradle for a full uninterrupted charge before taking it off the base. Li-ion cells shipped in storage state need a complete first cycle to let the BMS calibrate the state-of-charge register accurately.
Talk time shorter than the original battery after replacement
A new Li-ion cell ships partially charged and the BMS state-of-charge estimate is uncalibrated out of the box. The first two or three full charge-discharge cycles let the BMS learn the actual cell capacity and report it correctly. Until those cycles are complete, the handset may cut to low-battery warning earlier than expected. Run three full cycles — charge to full, use until the handset signals low battery, repeat — before judging capacity.
SpectraLink S35 handset loses DECT pairing after battery swap
Removing the battery cuts all power to the handset, which clears the volatile memory holding the DECT pairing data on some S35 firmware versions. The fix is to re-register the handset with the base station using the standard SpectraLink pairing procedure. On most S35 systems, this means holding the handset's registration button while the base is in pairing mode. Check the base station admin panel to confirm the handset slot shows as registered before returning the unit to service.