About this replacement
VeriFone CM5 — 3.85V Li-Polymer Replacement Battery (BPK278-501)
This is a 3.85V, 4000mAh Li-Polymer battery for the VeriFone CM5 mobile payment terminal. It replaces OEM part BPK278-501. The CM5 uses this flat-cell format to maintain its slim profile while powering the display, printer, and wireless radio simultaneously.
- CM5 platform fit: The CM5 draws from a single cell at 3.85V nominal, with the main board handling step-up conversion for the printer motor and backlight. This battery matches that voltage rail and carries the same BMS communication protocol the terminal expects on boot — no false low-battery flags on startup.
- Bench tested on actual hardware: We cycled this battery through the CM5's full boot sequence, including PCI handshake and printer initialisation. The BMS held the overcurrent threshold correctly during printer motor start, which briefly spikes draw above normal operating current.
- First deployment tip for the CM5: After installing this battery, run at least one complete transaction cycle — including a receipt print — before deploying the terminal live. The CM5 maps battery capacity during normal operation and needs one full power cycle to display the charge indicator accurately.
Payment terminal rebooting mid-transaction after battery swap
The CM5's receipt printer motor pulls a short, sharp current spike at the start of each print job. If the BMS on a new or degraded battery reads that spike as an overcurrent fault, it trips and the terminal drops power instantly — mid-sale. This battery's BMS is tuned to the CM5's printer motor profile and holds steady through that start-up surge. If the terminal still reboots after installation, confirm the battery is seated fully and the contact pads are clean before assuming a fault.
CM5 not completing PCI boot sequence after sitting unused
Li-Polymer cells self-discharge slowly during storage. If the CM5 has been in a drawer for several weeks, the cell voltage may have dropped below the terminal's minimum boot threshold — typically around 3.4V for this class of device. The terminal will not complete its PCI security boot below that level, so it either stalls at the splash screen or shows a low-battery error before the OS loads. Connect the terminal to a charger for at least 20 minutes before attempting to power it on, giving the cell enough voltage headroom to pass the boot sequence.