About this replacement
HP Pro Tablet 408 G1 — 3.8V Li-Polymer Replacement Battery (MLP3810980)
This 3.8V, 4800mAh Li-Polymer battery is a direct replacement for the HP Pro Tablet 408 G1. It fits models listed as I508O, T5L65PA, and L4A35UT. Install it when the original cell no longer holds charge or fails to bring the tablet to full power.
- Pro Tablet 408 G1 compatibility: The 408 G1, I508O, T5L65PA, and L4A35UT all share the same internal battery tray, connector pinout, and BMS handshake protocol. Swapping between these variants requires no hardware modification.
- Bench tested on actual hardware: We ran this cell through charge and discharge cycles on the 408 G1 platform. The BMS accepted the new cell without error flags, and charge IC communication stayed clean through full cycle.
- Fuel gauge recalibration after install: After fitting this battery, run one full discharge to automatic shutoff, then charge uninterrupted to 100%. The fuel gauge IC calibrates against the new cell during this cycle and clears the inaccurate percentage readings that typically appear right after a swap.
Tablet shutting down at 15–25% remaining after battery swap
The HP Pro Tablet 408 G1 draws a combined load from its display backlight, WiFi radio, and CPU simultaneously. Under that combined load, voltage drops faster than under light use. If the fuel gauge IC is still calibrated to the old, degraded cell, it misjudges the remaining capacity and triggers an emergency shutdown well above 0%. Running one full discharge-to-shutoff cycle lets the fuel gauge relearn the actual voltage curve of the new cell, and the early shutdowns stop.
Fast charging not available after fitting a new battery
Some users see the 408 G1 revert to standard charge rates after a battery replacement. The tablet's charge controller uses USB-PD negotiation, and it typically requires one accepted full charge cycle before re-enabling higher charge rates on a new cell. Plug into the original HP charger and let the tablet charge uninterrupted from low to 100%. After that first complete cycle, fast charge availability returns to normal.