About this replacement
Samsung Gear S2 Classic — 3.7V Li-Polymer Replacement Battery (EB-BR720ABE)
This is a 3.7V, 250mAh lithium-polymer cell for the Samsung Gear S2 Classic smartwatch. It fits SM-R720 and SM-R732 variants and the standard Gear S2. The EB-BR720ABE is the OEM part number this cell replaces.
- SM-R720 and SM-R732 compatibility: Both watch variants run the same power rail and use the same connector pinout and BMS handshake. A single cell covers both SKUs without modification.
- Bench tested on actual hardware: We ran this cell through charge and discharge cycles on SM-R720 hardware. The BMS accepted the cell without fault codes, and the fuel gauge IC reported capacity correctly after a full charge cycle from near-zero.
- Fuel gauge calibration after swap: After fitting the new cell, place the watch on its magnetic charger immediately and charge to 100% before first use. The fuel gauge IC on the Gear S2 platform loses its reference point when the original cell is removed — without a full charge cycle from near-zero, the gauge will misread state of charge and may show incorrect percentages throughout the day.
Why the Gear S2 drains a new cell faster than the old one in the first week
A fresh lithium-polymer cell has a different impedance profile than a degraded one. The Gear S2 power management IC adjusts draw thresholds based on learned cell behaviour, and that learning resets when you swap cells. For the first several charge cycles, the watch may draw at patterns that look aggressive against the new cell's impedance. This normalises after five to seven full cycles — no firmware change or setting adjustment is needed.
Watch not pairing to phone after battery replacement
Removing the battery terminates the active BLE session between the Gear S2 and the paired phone. The watch does not re-establish this automatically on power-up. Open the Galaxy Wearable app on the paired phone, go to the watch settings, and select Disconnect and Reset, then re-pair. The watch address does not change, so you do not need to delete the Bluetooth device from your phone first.