About this replacement
LG Optimus G2 Mini D620 Series — 3.7V Li-ion Replacement Battery (BL-59UH)
This is a 3.7V, 1600mAh Li-ion replacement battery for the LG Optimus G2 Mini and its D620 variants. It fits the D620, D620R, and D620J among other models in the series. Capacity is 5.92Wh — identical to the original BL-59UH specification.
- D620 series compatibility: The D620, D620R, D620J, and related variants all share the same battery bay dimensions, connector pinout, and BMS communication protocol. One cell fits the whole D620 line without modification.
- Bench tested on actual hardware: We ran this cell through full charge and discharge cycles on a D620 unit. The BMS handshake completed correctly, charge IC accepted the cell, and no error flags triggered during the test sequence.
- Fuel gauge recalibration on first install: On first use after installation, disable fast charging and run one full discharge-to-charge cycle without interruption. This lets the fuel gauge IC map the new cell's discharge curve before the charge controller begins applying higher current on subsequent cycles.
Why the G2 Mini reports wrong battery percentage after a cell swap
The G2 Mini uses a coulomb counter inside the fuel gauge IC to track charge state. That counter is calibrated against the original cell's internal resistance and discharge curve. When a new cell goes in, the old calibration data no longer matches the actual cell behaviour. The IC overcorrects or undercorrects its percentage estimate until it has completed at least one uninterrupted full cycle. After that cycle, the reported percentage stabilises and tracks the true charge state accurately.
Sudden shutdown at 20–30% on the replacement cell
This happens when the cell voltage drops sharply under load from the modem or display — the fuel gauge reads 20–30% but the cell can't sustain voltage when current demand spikes. The BMS trips a low-voltage cutoff to protect the cell before the gauge catches up. A full discharge-charge cycle recalibrates the IC, but if shutdowns continue after two cycles, check that resting voltage after a full charge reaches at least 4.15V. If it doesn't, the cell may have been stored below 2.5V and needs a slow recovery charge before normal use.