Grandstream WP820 Replacement Battery 3.7V 1200mAh Li-ion

Grandstream WP820 / DP730 / WP810 — 3.7V Li-ion Replacement Battery (GS-01)

This is a 3.7V, 1200mAh Li-ion replacement battery for the Grandstream WP820, DP730, WP810, and GMD1208 cordless handsets. It replaces OEM part number GS-01 and fits directly into the battery bay without modification. Capacity figures match the product data — 1200mAh / 4.44Wh.

• WP820, DP730, WP810, and GMD1208 compatibility: These four Grandstream handsets share the same 3.7V Li-ion cell form factor, connector pinout, and BMS voltage thresholds, which is why a single part number covers all of them.
• Bench tested on actual hardware: We cycled this cell on a WP820 handset and confirmed the BMS accepted charge from both the base cradle and USB-C port without triggering a fault state. Voltage at full charge settled at 4.18V — within the Li-ion upper cutoff window.
• First charge on a Li-ion handset swap: After installing this battery, seat the WP820 in its base cradle and let it charge uninterrupted until the handset indicator shows full. Li-ion cells shipped in storage state need one uninterrupted charge cycle to calibrate the fuel gauge accurately — pulling it early will cause the display to under-report remaining charge.

Why the WP820 shows a low battery warning sooner than expected after a replacement

The WP820 estimates remaining charge using a coulomb counter that tracks charge in and out of the cell. When a new battery arrives from storage, the counter has no baseline, so the handset's gauge starts from an incorrect reference point. This causes premature low-battery alerts even when actual capacity is fine. Two to three full charge-and-discharge cycles let the counter re-calibrate against the cell's real capacity. After that, the indicator aligns with actual charge state.

Handset loses DECT pairing after battery swap

Removing the battery on a DECT handset clears the volatile memory that holds the base station pairing record. This is a firmware behaviour — not a fault with the battery. To restore connection, press and hold the pairing button on the base station until it enters registration mode, then initiate pairing from the WP820 handset menu under Settings → DECT Registration. The handset should register within 60 seconds and return to normal operation.