About this replacement
Sony Ericsson Xperia ion LT28 Series — 3.7V Li-Polymer Replacement Battery (LIS1485ERPC)
This is a 3.7V, 1800mAh Li-Polymer replacement battery for the Sony Ericsson Xperia ion smartphone. It fits the LT28, LT28i, and LT28at model variants. Drop the original part numbers — it cross-references OEM codes 1251-9510.1, LIS1485ERPC, LIS1489ERPC, and 1251-9510.1C.
- LT28 variant compatibility: The LT28, LT28i, and LT28at share the same battery bay dimensions, connector pinout, and BMS handshake protocol. Swapping between these variants uses the same cell — voltage rail stays at 3.7V nominal across all three.
- Bench tested on actual hardware: We ran this cell on an LT28i and monitored the BMS during charge cycles. The protection circuit engaged at both the 4.2V charge cutoff and the low-voltage discharge floor without fault codes.
- Fuel gauge recalibration after install: On first use after swapping this cell in, let the phone discharge to automatic shutdown, then charge to 100% without interruption. The Xperia ion's fuel gauge IC maps its charge curve to the new cell during this first full cycle — skipping it causes the percentage counter to read inaccurately for days.
Why the Xperia ion reports wrong battery percentage after a cell swap
The Xperia ion uses a coulomb counter in its fuel gauge IC that was calibrated to the discharge curve of the original cell. When a new cell goes in, that stored curve no longer matches actual cell behaviour. The IC continues using the old data until it completes a full discharge-to-charge cycle with the new cell. Until that cycle runs, percentage readings can sit 10–20% above or below actual charge state.
Sudden shutdown at 20–30% on the replacement cell
This happens when the cell voltage drops below the modem or display's minimum operating threshold before the percentage counter reaches zero — a voltage cliff caused by the uncalibrated fuel gauge IC. The phone sees 25% remaining but the cell is already sagging under load. The fix is the same full recalibration cycle: discharge completely to auto-shutdown, then charge uninterrupted to 100%. After one complete cycle, the IC anchors its model to the new cell's actual 3.0V floor.