Maxon MX X3 Replacement Battery 3.7V 2600mAh Li-Polymer

Maxon MX X3 — 3.7V Li-Polymer 2600mAh Replacement Battery

This 3.7V, 2600mAh Li-Polymer cell replaces the original battery in the Maxon MX X3 and MX-X3 smartphone, including T-King-branded variants. It measures 83.60 × 64.00 × 4.25mm and matches the original connector and contact layout. Capacity figure is 9.62Wh as rated — use the product data, not third-party listings.

• MX X3 and T-King MX-X3 fitment: Both the Maxon and T-King variants of this phone share the same chassis dimensions, connector pinout, and charge IC configuration, so one cell covers all four listed model strings without modification.
• Bench tested on actual hardware: We cycled this cell through charge and discharge on the MX X3 platform and confirmed the BMS communicates correctly with the phone's fuel gauge IC — no rogue cutoff, no false full-charge flag on the first cycle.
• Fuel gauge recalibration on first use: On first use after installation, disable fast charging for one complete discharge-charge cycle. This lets the fuel gauge IC map its coulomb counter against the new cell's actual discharge curve before high-current charging runs into an uncalibrated state.

Sudden shutdown at 20–30% on the replacement cell

A new Li-Polymer cell has a slightly different voltage-versus-capacity curve than the aged cell the phone's fuel gauge IC learned on. When the modem fires a transmission burst or the screen peaks, the cell voltage briefly drops below the BMS cutoff threshold — even at what the OS reads as 25%. The fuel gauge IC has not yet correlated its coulomb counter to the new discharge curve, so it cannot predict the real remaining capacity. One full discharge-charge cycle without fast charging resets the calibration and eliminates most of these phantom shutdowns.

Phone will not power on after the battery sat in storage

Li-Polymer cells in storage self-discharge over weeks. If the cell voltage drops below roughly 2.5V, the BMS enters a lockout state and blocks normal charge current to prevent thermal runaway on a deeply discharged cell. Plugging in and seeing no charging indicator is the tell. Apply a slow trickle charge — leave the phone connected to a low-power 5V USB source for 20 to 30 minutes before attempting a normal boot. Once the cell recovers above the BMS re-enable threshold, the charger IC resumes and the phone powers on normally.