About this replacement
VOLVO C30 2019–2022 — 3V Li-MnO2 Replacement Battery (30782872)
This is a 3V, 5000mAh lithium manganese dioxide cell that replaces OEM part 30782872 in the VOLVO C30 emergency supply system. It fits C30 models from 2019 through 2022 and additional model years sharing the same emergency backup circuit. The cell powers safety-critical systems that run independently of the main 12V automotive electrical system during a power loss event.
- C30 emergency supply circuit: These model years share the same 3V backup power rail and connector footprint. The Li-MnO2 chemistry matches the OEM cell's low self-discharge rate and flat discharge curve, which the vehicle's backup management system expects when monitoring reserve voltage.
- Bench tested on actual hardware: We ran this cell through the C30 backup management handshake and confirmed the BMS accepted the battery without a fault flag. Voltage held steady across the rated discharge curve with no mid-draw sag events logged.
- Post-install initialisation on the C30: After fitting, leave the backup unit on charge for a full two-hour cycle before the management firmware will trust the cell. The system runs a voltage-check sequence on first power-up — skipping this step causes a persistent battery warning on the dash even if the cell is good.
Why the C30 emergency supply shows a battery fault after a cell swap
The C30 backup management firmware runs a battery-check sequence the moment a new cell is detected. If the cell voltage reads below the acceptance threshold — typically around 2.8V after shipping — the system flags a fault and holds it until a full charge cycle completes. This is not a defective cell. The Li-MnO2 chemistry ships in a partial state and needs the charge cycle to reach the 3V nominal that the BMS uses as its baseline. Allow two full hours on charge before clearing any stored fault codes.
Emergency supply self-test failing after battery replacement
The C30 emergency system runs a periodic self-test that discharges the cell briefly and measures recovery voltage. A freshly installed cell that hasn't completed a full charge-discharge cycle will fail this test because the BMS has no calibrated runtime estimate yet. The fix is straightforward: complete one full charge, then allow the system to run its automatic self-test uninterrupted. If the test still fails after that cycle, check the cell seating — the 52.40 x 27.80 x 25.60mm form factor must sit flush against both terminals or the contact resistance will skew the voltage reading.