About this replacement
Lenovo Legion Y700 / TB-9707F — 3.87V Li-Polymer Replacement Battery (L21C2P32)
This is a 3.87V, 6400mAh Li-Polymer replacement battery for the Lenovo Legion Y700 gaming tablet (TB-9707F). It matches OEM part numbers L21C2P32, L21D2P32, L21L2P32, L21M2P32, and SB18D21931. Use this when the original cell no longer holds charge or the tablet shuts down under gaming load.
- Legion Y700 and TB-9707F compatibility: Both model designations reference the same hardware generation. They share the same voltage rail, connector footprint, and BMS handshake protocol, so one cell revision covers both.
- Bench tested on actual hardware: We cycled this battery through charge and discharge on a TB-9707F board. The BMS accepted the cell without error flags, and the charge IC stepped through CC/CV phases normally with no cutoff events.
- Fuel gauge recalibration after swap: After installation, run one full discharge to automatic shutoff, then charge uninterrupted to 100%. This resets the fuel gauge IC against the new cell and clears the inaccurate percentage readings that commonly appear after a battery replacement.
Legion Y700 shutting down at 15–25% during gaming sessions
The Legion Y700 pulls simultaneous load from the display, GPU, and WiFi radio during active gameplay. At around 3.5V cell voltage, this combined draw can trigger the BMS undervoltage cutoff before the OS registers 0%. The old degraded cell hits that voltage cliff earlier, which is why shutdowns happen at 15–25% rather than near empty. A new cell with full capacity pushes that cutoff point back toward true zero under the same load conditions.
Fast charging not available after battery replacement
The Legion Y700 uses a proprietary fast charge protocol that the charge IC re-negotiates during the first accepted charge cycle on a new cell. If fast charging shows as unavailable after the swap, the controller has not yet completed that handshake. Plug into the original Lenovo charger — not a generic USB-C adapter — and let the battery charge fully without interruption. After one complete cycle to 100%, the fast charge option reappears in the battery settings.