About this replacement
Lenovo K5 Play / L38021 — 3.85V Li-Polymer Replacement Battery (BL289)
This is a 3.85V, 3000mAh (11.55Wh) Li-Polymer replacement battery for the Lenovo K5 Play (L38021). It carries part number BL289 and slots directly into the phone's battery bay. Use this when the original cell no longer holds charge or the phone shuts down unexpectedly under load.
- K5 Play and L38021 compatibility: Both model designations refer to the same handset released across different regional markets. They share the same battery cavity dimensions, connector pinout, and BMS handshake protocol — one BL289 cell covers both.
- Bench tested on actual hardware: We cycled this cell through full charge and discharge on a K5 Play unit. The BMS accepted the charge handshake without fault codes, and voltage held within spec across the full discharge curve from 4.35V down to the 3.0V cutoff.
- Fuel gauge recalibration on first use: After fitting this cell, disable fast charging and run one complete discharge-charge cycle at standard rate. The K5 Play's fuel gauge IC was calibrated against the original cell's discharge curve — one full cycle lets it remap against the new cell before fast charging pushes higher current into an uncalibrated state.
Sudden shutdown at 20–30% on the K5 Play after a cell swap
A fresh cell's voltage curve doesn't match the profile the fuel gauge IC learned from the aged original. When the phone estimates 25% remaining, the new cell's actual voltage may already be approaching the threshold where modem and display load pull it below 3.4V. The phone interprets that voltage sag as a fault and cuts power — not because the battery is failing, but because the IC is reading from the wrong map. One full discharge-charge cycle at standard charge rate forces the coulomb counter to resync to the new cell's actual curve, and the shutdowns stop.
K5 Play not powering on after the replacement battery sat in storage
Li-Polymer cells self-discharge in storage. If the BL289 cell dropped below 2.5V before installation, the BMS may have entered lockout mode to protect the cell from deep-discharge damage. The phone will show no response — no charging indicator, no boot screen. Connect the phone to a wall charger rated at 5V/1A or higher and leave it for 20–30 minutes without pressing the power button; the charge IC needs to trickle current into the cell until it clears the BMS lockout threshold before the phone will respond. Once you see the charging indicator appear, the cell has recovered above the minimum threshold and normal charging will resume.