About this replacement
Highscreen Spark 2 — 3.7V Li-ion Replacement Battery
This 3.7V, 1250mAh Li-ion cell is a direct replacement for the Highscreen Spark 2 smartphone. It fits the Spark 2 battery bay and connects to the original charge IC and fuel gauge circuitry. Capacity is 1250mAh (4.63Wh) — matched to the factory spec.
- Spark 2 battery bay fit: The Spark 2 uses a removable single-cell Li-ion pack at 3.7V nominal. This replacement matches the connector pinout and cell dimensions, so the BMS on the mainboard reads the new cell without flagging a hardware mismatch.
- Bench tested on actual hardware: We cycled this cell through charge and discharge on a Spark 2 mainboard. The charge IC accepted the cell on first connection, BMS protection triggers fired correctly at low-voltage cutoff, and the fuel gauge IC registered cell state without error flags.
- First-cycle recalibration on the Spark 2: After installation, disable fast charging for one full discharge-charge cycle. The Spark 2 fuel gauge IC is calibrated to the old cell's discharge curve. Running one slow cycle first lets the coulomb counter map the new cell before high-current charging pushes current into an uncalibrated state.
Why the Spark 2 reports wrong battery percentage after a cell swap
The Spark 2 uses a fuel gauge IC that tracks charge by counting coulombs against a stored discharge curve from the original cell. When you swap to a new cell, that stored curve no longer matches actual cell behaviour. The gauge reads state-of-charge from the wrong reference, so the percentage shown on screen drifts from reality. One full slow charge-discharge cycle overwrites the reference and brings the percentage display back into alignment.
Sudden shutdown at 20–30% on the replacement cell
This happens when the cell voltage drops below the modem or display load threshold before the fuel gauge predicts it will. A new cell with a slightly different internal resistance curve can hit a voltage cliff earlier than the IC expects under high-draw moments — screen-on, active data, or a call. The BMS cuts output to protect the cell, and the phone shuts off with charge still showing. Run two full discharge cycles without heavy load to let the fuel gauge recalibrate the low-voltage endpoint; the shutdowns typically stop once the counter maps the real cutoff voltage, around 3.4–3.5V under load.