About this replacement
Acer Liquid Z4 / Z140 / Z160 — 3.7V Li-ion Replacement Battery (BAT-611)
This is a 3.7V, 1250mAh Li-ion replacement battery for the Acer Liquid Z4, Z140, and Z160 smartphones. OEM part numbers BAT-611 and KT.0010B.006 both apply to this cell. It slots directly into the rear battery compartment and powers the processor, display, and all wireless functions.
- Z4 / Z140 / Z160 platform fit: These three models share the same battery bay dimensions, connector pinout, and BMS handshake protocol — one cell covers all three. The 64.85 × 49.45 × 4.45mm form factor matches the original chassis tolerances without modification.
- Bench tested on actual hardware: We cycled this cell through a full charge and discharge sequence on the Liquid Z4. The BMS accepted the cell on first connection, voltage sat at 3.7V nominal under screen-on load, and the charge IC completed a clean taper cycle without tripping a protection flag.
- Fuel gauge recalibration on first use: After installation, disable fast charging and run one complete discharge-charge cycle at standard rate. This lets the fuel gauge IC map the new cell's discharge curve before high-current charging begins on an uncalibrated cell — skipping this step causes erratic percentage readings from the first charge onward.
Why the Liquid Z4 reports wrong battery percentage after a cell swap
The Liquid Z4 uses a coulomb-counter-based fuel gauge IC that holds calibration data from the original cell's charge curve. When a new cell goes in, the IC is still referencing the old curve — so reported percentage drifts away from actual state of charge almost immediately. The fix is one full discharge to near-empty followed by an uninterrupted charge to 100% at standard rate, no fast charging. After that cycle, the IC re-anchors its empty and full reference points to the new cell. Expect the percentage display to stabilise from the second cycle onward.
Sudden shutdown at 20–30% on the replacement cell
This happens when the cell voltage drops sharply under combined modem and display load — a voltage cliff the fuel gauge didn't predict because it hasn't completed a calibration cycle. The phone's protection circuit trips the shutdown before the display reads zero. It is not a faulty battery. Run the device down to automatic shutoff once, then charge fully to 100% without interruption. After that, the fuel gauge has a real low-voltage anchor and the shutdowns stop.