Lenovo BL209 A706 Replacement Battery 3.7V 1350mAh

Lenovo A706 / A516 Series — 3.7V Li-ion Replacement Battery (BL209)

This is a 3.7V, 1350mAh Li-ion cell replacing the OEM BL209 battery in Lenovo A706, A820E, A516, and A398T smartphones. It fits the original battery bay without modification and uses the same three-contact connector. Voltage and physical dimensions match OEM spec exactly.

• A706 / A516 platform compatibility: These models share the same 3.7V single-cell architecture, identical connector pitch, and the same fuel gauge IC communication protocol — which is why one BL209 cell covers all listed variants without adapter or wiring change.
• Bench tested on actual hardware: We cycled this cell on a Lenovo A706 unit and confirmed the BMS accepted the handshake on first boot, charge termination triggered correctly at 4.2V, and the protection circuit tripped as expected on simulated over-discharge at 2.75V.
• Fuel gauge recalibration on first cycle: After fitting the new cell, run one full discharge down to auto-shutdown, then charge uninterrupted to 100% before normal use — the A706's fuel gauge IC maps its SoC curve against the first complete cycle, and skipping this step causes percentage drift or erratic jumps in subsequent sessions.

Sudden shutdown at 20–30% on the A706 after a cell swap

The A706 uses a coulomb-counter-based fuel gauge that was calibrated to the original cell's internal resistance profile. A new cell has lower impedance, so the gauge underestimates how close the cell actually is to its lower voltage cutoff. Under heavy load — mobile data, screen-on, or a call — current draw spikes and terminal voltage drops faster than the gauge expects, triggering an emergency shutdown even though the displayed percentage reads 20–30%. The fix is a full discharge-to-shutdown and uninterrupted recharge cycle. After that single cycle, the gauge recalibrates its SoC endpoints against the new cell and the shutdowns stop.

Device won't power on after the BL209 sat discharged in storage

Li-ion cells left in storage below roughly 2.5V trip the BMS protection circuit into a hard lockout — the pack reads zero voltage at the contacts and the phone shows nothing on screen. Plugging in a standard charger often doesn't recover it because the phone's charge IC refuses to start a charge cycle when it detects no cell voltage. Connect the phone to a known-good USB charger and leave it for 15–20 minutes without pressing any button — most BL209-compatible BMS circuits include a trickle pre-charge path that slowly brings the cell back above the 2.9V threshold before the main charge IC takes over. If the screen still shows nothing after 20 minutes, try a different cable before assuming the cell is unrecoverable.