About this replacement
Enspert ESP E201U / Identity 7 — 3.8V Li-Polymer Replacement Battery (OS5AU400WO)
This is a 3.8V, 3800mAh Li-Polymer cell that replaces part number OS5AU400WO in the Enspert ESP E201U and Identity 7 tablets. It powers the display, processor, and all onboard components. Capacity figure comes from the product data: 3800mAh / 14.44Wh.
- ESP E201U and Identity 7 fit: Both tablets share the same battery bay dimensions, connector pinout, and BMS handshake protocol — 85.75 × 53.44 × 6.20mm with identical voltage rail at 3.8V nominal. One replacement cell covers both models.
- Bench tested on actual hardware: We ran this cell through charge acceptance and BMS communication on an ESP E201U unit. The protection circuit responded correctly to charge termination and over-discharge cutoff at the expected voltage thresholds.
- Fuel gauge recalibration after swap: After installation, run the tablet down to automatic shutoff, then charge uninterrupted to 100% without interruption. This forces the fuel gauge IC to recalibrate against the new cell's actual capacity curve and clears the inaccurate percentage readings that commonly appear right after a battery swap.
Tablet shutting down between 15–25% after battery replacement
This happens because the fuel gauge IC still holds calibration data from the old, degraded cell. When the display and Wi-Fi draw current simultaneously, voltage sags faster than the gauge predicts, and the protection circuit trips the cutoff before the percentage reaches zero. The tablet interprets this as a shutdown event, not a fault. One complete discharge-to-shutoff cycle followed by an uninterrupted charge to 100% resets the gauge. After that cycle, the remaining-charge readout tracks accurately against the new cell's actual 3800mAh capacity.
Fast charging unavailable after fitting the OS5AU400WO replacement cell
Some ESP E201U units withhold fast-charge negotiation until the charge IC has completed at least one full accepted charge cycle on the new cell. The tablet communicates with the battery's BMS before enabling higher current draw — on a fresh cell, that handshake may not resolve on the first plug-in. Connect to the original Enspert charger and allow one complete charge from low to 100% without interrupting. After that cycle, fast-charge availability typically restores. If it does not, verify the charger outputs the correct voltage — the tablet expects 5V nominal on the USB input.