About this replacement
Fieldbook K80 Series — 3.7V Li-Polymer Replacement Battery (MLP427488-2P)
This is a 3.7V, 7000mAh Li-Polymer replacement battery for the Fieldbook K80, K80 G2, and Rugline RT86 Industrie Tablet. It uses OEM part number MLP427488-2P and slots into the same battery bay as the original cell. Capacity is 25.9Wh — matching the stock specification.
- K80, K80 G2, and RT86 compatibility: All three tablets share the same MLP427488-2P cell footprint, connector pinout, and BMS communication protocol. The same replacement covers all three without modification.
- Bench tested on actual hardware: We ran this cell through charge and discharge cycles on the K80 platform. The BMS handshake completed normally on first boot, charge acceptance began immediately, and no protection trip events occurred during testing.
- Fuel gauge recalibration after install: After fitting this battery, run one full discharge to automatic shutoff, then charge uninterrupted to 100%. This resets the fuel gauge IC against the new cell and corrects the percentage drift that commonly appears after a battery swap.
Fieldbook K80 shutting down between 15% and 25% remaining
The K80 shuts down early because the display backlight and active WiFi together pull enough current to cause a sharp voltage sag in a degraded or freshly swapped cell. The fuel gauge IC reads the sag as a critically low state-of-charge and triggers a hard cutoff before the displayed percentage reaches zero. A new cell still calibrated to the old battery's discharge curve will replicate this behaviour until recalibrated. Run one full discharge-to-shutoff cycle followed by an uninterrupted charge to 100% — after that cycle the IC maps the correct voltage floor for this cell and the early shutoff stops.
Fast charging unavailable on the K80 after battery replacement
The K80's charge controller uses USB-PD negotiation to decide whether to enable fast charging. On a freshly installed cell, the BMS may not complete that handshake on the first accepted charge cycle. Plug into the original Fieldbook charger — not a generic 5V adapter — and allow one full charge to complete without interruption. After that first accepted cycle, the charge IC recognises the new cell's internal resistance profile and re-enables the higher charge rate. Confirm fast charging is active by checking the charging indicator or Settings → Battery on the next plug-in.