About this replacement
Wexler E5001 — 3.7V Li-Polymer Replacement Battery (YT453949)
This is a 3.7V, 800mAh lithium-polymer cell replacing part number YT453949 in the Wexler E5001 e-reader. It fits directly into the E5001 chassis and restores power to the e-ink display, page-turn controls, and USB charging circuit. Capacity matches the original specification at 2.96Wh.
- E5001 cell format: The E5001 uses a slim 45.80 × 37.64 × 4.50mm pouch cell — a form factor chosen to keep the reader thin. The connector and polarity match the original YT453949 exactly, so no wiring modification is needed.
- Bench tested on actual hardware: We cycled this cell through charge and discharge on the E5001 board and confirmed the BMS accepted the cell without triggering a fault. The protection circuit responded correctly to both over-charge cutoff and low-voltage cutoff thresholds.
- Post-swap charge cycle: After fitting this cell, connect the E5001 to USB power and let it charge uninterrupted to 100% before first use. The e-reader firmware recalibrates its battery percentage display against a full charge cycle — skipping this step causes inaccurate readings from the first boot.
Why the E5001 battery percentage jumps after a cell swap
The E5001 firmware tracks battery state using a coulomb counter that was calibrated to the old, degraded cell. When a new cell goes in, the counter has no reference point for the fresh capacity curve. This causes the displayed percentage to jump — sometimes showing 80% then dropping to 20% within a few page turns. One full charge-to-discharge cycle resets the counter's reference and stabilises the readout.
E5001 showing low battery immediately after new cell installed
Replacement cells ship at storage voltage — typically around 3.6–3.7V — which sits below the threshold the E5001 firmware treats as a healthy charge state. The device reads this as a near-empty battery and displays the low battery warning before you even open a book. This is not a faulty cell. Connect the E5001 to a USB charger and charge it fully to 4.2V before attempting to power on normally.