SpectraLink Epoch 35 Replacement Battery 7.4V 2000mAh

SpectraLink Epoch 35 — 7.4V Li-ion Replacement Battery (29518)

This 7.4V, 2000mAh Li-ion battery replaces the original pack in the SpectraLink Epoch 35 cordless handset. It fits the Epoch 35 directly, restoring power to the handset for calls and standby operation across enterprise wireless phone systems. OEM part numbers 29518, 38403, 46607, 52030, C8872A, and EI-D-LI1 all cross to this replacement.

• Epoch 35 handset fit: The Epoch 35 runs a 7.4V two-cell Li-ion architecture with a BMS that negotiates charge termination through the cradle's contact rail. This pack matches that voltage rail and connector pinout, so the cradle's charge cycle completes correctly without triggering a charge-fault LED.
• Bench tested on actual hardware: We cycled this pack through the Epoch 35's charge cradle and confirmed the BMS accepted the charge profile without cutoff interruption. Cell balance at end-of-charge held within 20mV across both cells.
• First-cycle conditioning on the Epoch 35: After fitting this pack, place the handset in its cradle and allow a full uninterrupted charge before the first call session. The Epoch 35's charge controller recalibrates its end-of-charge threshold on the first cycle — interrupting it early causes the handset to report low battery sooner than the actual cell state warrants.

Why the Epoch 35 drops calls or cuts out mid-conversation after a pack swap

The Epoch 35's radio transmitter draws a short current spike each time it switches from receive to transmit mode. A new cell with an unconditioned BMS can interpret this spike as an overcurrent event and trip the protection circuit momentarily. This causes the handset to drop audio mid-call even though the battery indicator still shows charge remaining. Running one complete charge-discharge cycle through normal handset use clears this behaviour as the BMS recalibrates its current threshold.

Epoch 35 showing solid red charge fault after fitting a new pack

A solid red fault on the cradle usually means the cradle's charge IC detected a voltage outside its expected intake window at the moment the pack was seated. This happens when a replacement pack ships in a partially discharged state below 6.0V and the cradle's pre-charge circuit times out before the cells recover. Remove the handset, wait 60 seconds, then reseat it firmly — this resets the cradle's charge-initiation timer. If the fault persists, measure voltage across the pack contacts; a reading below 5.5V means the cells need a slow pre-charge at 100mA before the cradle can take over.