About this replacement
Clover C401U / FLEX — 7.6V Li-Polymer Replacement Battery (MPPCLOYJ4)
This 7.6V, 2100mAh Li-Polymer battery replaces the original cell in the Clover C401U and FLEX portable payment terminals. It matches the OEM voltage rail, connector, and BMS communication protocol used on both models. Capacity figure is taken directly from product specifications — 15.96Wh total.
- C401U and FLEX compatibility: Both terminals share the same battery bay format, connector pinout, and BMS handshake sequence. A single cell covers both models without modification.
- Bench tested on actual hardware: We cycled this battery through full charge and discharge on a C401U unit. The BMS accepted the cell on first boot, voltage held steady at 7.6V under combined display, wireless, and printer load, and the protection circuit tripped correctly at the low-voltage cutoff threshold.
- First-deployment cycle on a live terminal: After installation, run at least one complete transaction — including receipt print — before putting the terminal into service. The Clover charge IC maps cell capacity during normal operation and requires a full power cycle to report the charge indicator accurately on the screen.
Why the C401U reboots mid-transaction after a battery swap
The receipt printer motor draws a sharp current spike at the moment it fires — typically lasting under a second but large enough to trip the BMS overcurrent threshold on a new cell that has not yet completed a full charge cycle. The BMS interprets that spike as a fault and cuts output voltage, which forces a hard reboot. Charging the battery to 100% before first use and completing one full transaction cycle lets the BMS calibrate its overcurrent window to the terminal's actual load profile. After that initial cycle, mid-transaction reboots caused by this issue stop.
Terminal not powering on after sitting unused in storage
Li-Polymer cells self-discharge during storage, and if the voltage drops below approximately 2.5V per cell, the BMS enters a deep-discharge lockout state and will not pass current to the terminal. The terminal shows no response — no boot screen, no charging indicator — which looks identical to a dead battery but is actually a recoverable condition. Connect the terminal to its original charger and leave it undisturbed for 20–30 minutes without pressing the power button. The charge IC applies a low-current pre-charge to bring the cell voltage back above the BMS recovery threshold, typically around 3.0V, at which point normal charging resumes.