About this replacement
RUNBO X3 / X5 Series — 3.7V Li-ion Replacement Battery (A380)
This is a 3.7V 3000mAh (11.1Wh) Li-ion cell that replaces the original A380 battery in the RUNBO X3, X5, X5-C, and X5-W rugged smartphones. These phones take hard use in field and industrial environments, and the original cell typically degrades well before the chassis does. This replacement restores full charge capacity to the device.
- X3, X5, X5-C, and X5-W compatibility: All four models share the same battery bay dimensions and the A380 part number. The connector pinout and BMS handshake protocol are consistent across the series, so a single cell covers the entire platform.
- Bench tested on actual hardware: We ran this cell through charge and discharge cycles on the X5 platform. The BMS accepted the charge without fault flags, voltage held steady across screen-on and modem-active load, and the protection circuit tripped correctly at the expected low-voltage cutoff threshold.
- Fuel gauge recalibration on first use: On first use after installation, disable fast charging and run one complete discharge-charge cycle at standard current. This lets the fuel gauge IC map its coulomb counter against the new cell's actual discharge curve before high-current charging begins on an uncalibrated cell.
Sudden shutdown at 20–30% on the RUNBO X3 after a cell swap
The RUNBO X3 uses a fuel gauge IC that stores a learned discharge curve from the original cell. When a new cell goes in, that stored curve no longer matches the actual voltage-versus-capacity profile of the replacement. The phone's modem and display draw current spikes that briefly pull cell voltage below the shutdown threshold — even when the gauge still reads 20–30%. The fix is one full discharge to auto-off, followed by an uninterrupted charge to 100%, which forces the IC to relearn the new curve. After that cycle, the voltage cliff behaviour typically stops.
Device will not power on after the replacement battery sat in storage
Li-ion cells self-discharge in storage, and if a replacement cell drops below approximately 2.5V per cell, the BMS enters lockout mode to prevent damage. Plugging in the charger at this point often shows no response — no charge indicator, no boot. Connect the phone to a wall adapter (not a USB port) and leave it for 15–20 minutes without attempting to power on. The charge IC will trickle current into the cell until voltage climbs above the BMS re-enable threshold, typically around 2.9–3.0V, at which point normal charging resumes.