About this replacement
COWIN E7 / E7 Pro — 3.7V Li-Polymer Replacement Battery (AHT903450)
This 3.7V, 1800mAh Li-Polymer cell replaces the internal battery in the COWIN E7 and E7 Pro over-ear wireless headphones. It restores power to the Bluetooth radio, active noise cancellation circuit, and onboard controls. OEM part number is AHT903450.
- E7 and E7 Pro compatibility: Both models share the same battery bay dimensions, connector pinout, and BMS voltage thresholds. The cell sits in a 52.80 × 33.50 × 9.00mm envelope — the E7 Pro does not use a larger pack despite its extended feature set.
- Bench tested on actual hardware: We cycled this cell through the E7's charge circuit and confirmed the BMS accepted the pack, raised voltage cleanly from storage level to 4.2V, and released the protection latch at end-of-charge without error flags.
- ANC draw on first charge: The E7's noise-cancellation circuit pulls continuous current on top of the Bluetooth radio load. On the first charge after fitting this cell, leave ANC off until the pack completes one full charge cycle — the BMS calibrates its state-of-charge estimate against a stable load baseline.
Why the E7 cuts out mid-call on a new battery
A fresh Li-Polymer cell ships at storage voltage — typically around 3.6–3.7V. The E7's combined Bluetooth and ANC draw creates a brief current spike that can push the BMS into undervoltage protection before the cell has been conditioned. The protection latch trips and the headset goes silent. One full charge cycle brings the cell to 4.2V and lets the BMS set accurate cutoff thresholds, eliminating the false trip.
Talk time noticeably shorter in the first few uses after replacement
Li-Polymer cells don't deliver full rated capacity on cycle one. Internal resistance is slightly elevated out of the box, and the BMS hasn't yet mapped the cell's actual charge curve. Usable capacity steps up across three to five full charge-discharge cycles as the cell settles. By cycle five, you should see capacity close to the rated 1800mAh — if talk time is still short after that, check that the charging cable is delivering a stable 5V to the headset's micro-USB port.