About this replacement
ZTE Blade A601 — 3.8V Li-Polymer Replacement Battery (ICP51/59/78SA)
This is a 3.8V, 4000mAh Li-Polymer battery for the ZTE Blade A601 (BA601). It replaces OEM part ICP51/59/78SA and fits the original battery bay without modification. Capacity is 15.2Wh — matching the stock specification from the product data.
- Blade A601 and BA601 compatibility: Both model designations share the same battery bay dimensions, connector pinout, and BMS handshake protocol. The 80.00 × 58.50 × 5.00mm cell fits the housing correctly and the fuel gauge IC communicates over the same data line as the original cell.
- Bench tested on actual hardware: We ran this cell through charge and discharge cycles on a ZTE Blade A601 unit. The BMS accepted the cell without error flags, charge current ramped correctly through CC/CV phases, and the protection circuit tripped normally at the low-voltage cutoff threshold.
- Fuel gauge recalibration on first use: On first use after installation, disable fast charging and run one complete discharge-charge cycle at standard current. This lets the fuel gauge IC map the new cell's discharge curve before high-current charging pushes current into an uncalibrated state — preventing erratic percentage readings from the first charge onward.
Sudden shutdown at 20–30% on the Blade A601 after a cell swap
The Blade A601's fuel gauge IC stores a charge curve calibrated to the original cell. A new cell with a slightly different internal resistance profile causes the IC to misread remaining capacity under load. When the modem transmits or the screen peaks brightness, current draw spikes and the cell voltage drops below the BMS cutoff threshold before the percentage display reaches zero. One full discharge-charge cycle at standard current overwrites the stored curve and the shutdowns stop.
Phone shows 100% immediately after plugging in the replacement cell
This happens when the coulomb counter in the fuel gauge IC carries over its last state from the old cell. The new cell's actual state of charge does not match the register value the OS is reading. The fix is straightforward: run the phone down until it powers off from low battery, then charge uninterrupted to full. After that single cycle the coulomb counter resets against the new cell and the percentage tracks accurately at every charge level.