What is a BMS module and why does it fail?
A Battery Management System (BMS) is the electronic brain of every lithium battery pack — Li-Ion, LiFePO4, Li-NMC or Li-titanate. It monitors cell voltages, balances charge between individual cells, measures current and temperature, communicates pack status via CAN bus, SMBus or Modbus, and protects the cells from overvoltage, undervoltage, overcurrent and thermal runaway. When the BMS fails, the entire battery becomes inoperative regardless of whether the cells themselves are healthy.
Acore services BMS modules from electric forklifts (Linde, Toyota, Jungheinrich, Still, BT, Crown, Yale, Hyster, Mitsubishi), industrial drones (DJI Matrice, Freefly Alta, Inspired Flight IF1200), AGV and AMR platforms, inverter welders and grid-scale ESS systems. Our workshop is located in Knurow, Silesia, Poland — with nationwide courier service and on-site repair for fleet customers.
Most common BMS failure modes
| Failure type | Symptoms | Root cause | Repair cost |
|---|---|---|---|
| MOSFET transistor failure | Battery does not charge or discharge, blown fuse | Short circuit, overvoltage, overcurrent | EUR 70–210 |
| Cell balancer IC failure | Uneven cell voltages, rapid capacity loss | Internal IC damage | EUR 90–280 |
| Microcontroller / MCU failure | No CAN/SMBus communication, display dead | Overvoltage, moisture, corrosion | EUR 115–420 |
| CAN bus transceiver failure | No communication with vehicle controller | Bus overvoltage, ESD | EUR 60–165 |
| Shunt resistor damage | Incorrect current reading, false alarms | Current overload | EUR 50–115 |
BMS applications we repair
Electric forklifts (24V–96V)
Modern LiFePO4 forklift batteries from Linde, Toyota, Jungheinrich and Still use BMS modules communicating over CAN ISO 11898 with the VCM. Common fault codes pointing to BMS failure: Linde E210/E215/E270, Jungheinrich 10xx/11xx, Toyota 53-1/53-2, Still C1xxx. Repair avoids battery replacement costs of EUR 8 000–20 000.
Industrial drones (6S–12S)
DJI Matrice 300, Freefly Alta 8, Quantum Systems Trinity and Inspired Flight IF1200 use 44.4V–51.8V smart battery packs. BMS failures in drones typically involve op-amp measurement circuits and MOSFET gate drivers damaged by high inrush currents during BLDC motor startup. New OEM batteries cost EUR 800–2200; BMS repair costs EUR 90–280.
AGV / AMR platforms
Autonomous vehicle batteries (STILL, Kivnon, Aethon, Geek+) run on 24V–48V LiFePO4 packs with CANopen or EtherCAT BMS communication. Downtime for a single AGV can halt an entire production line — Acore offers 24-hour priority repair for fleet operators under a service agreement.
Repair process
- Incoming inspection — cell voltage measurement, isolation test (IR > 1 MOhm), fault code readout via CAN/SMBus.
- PCB visual inspection — 10x loupe, solder joints, SMD and THT components, signs of burning, corrosion, moisture damage.
- Electrical measurements — oscilloscope on MOSFET gate/source rails, shunt resistor measurement, balancer IC reference voltage test.
- Component replacement — SMD rework station (850°C hot air), MOSFET replacement (IRFB4115, IRFB7430, CSD19505KCS), balancer ICs, CAN transceivers (TJA1051, SN65HVD230).
- Programming and calibration — firmware via JTAG/UART/SMBus, SOC/SOH calibration, temperature and current limit setup.
- Cycle testing — 3–5 charge/discharge cycles on Chroma 17200 or Digatron BTS-600, cell balance verification (delta < 10 mV).
Repair cost vs. replacement
| Battery / Application | New battery price | BMS repair cost | Savings |
|---|---|---|---|
| Forklift 48V/400Ah LiFePO4 | EUR 8 000–18 000 | EUR 190–1 050 | up to 97% |
| AGV/AMR 48V/100Ah | EUR 2 800–5 800 | EUR 140–470 | up to 95% |
| Industrial drone 44.4V/20Ah | EUR 820–2 100 | EUR 90–280 | up to 88% |
FAQ
- Can a BMS be repaired without replacing the whole battery?
- Yes — in about 85% of cases the fault is in the BMS electronics, not the cells. If cell capacity exceeds 70% of nominal and cell voltage delta is under 50 mV, repairing the BMS restores full battery functionality.
- How long does BMS repair take?
- Standard turnaround is 2–5 business days (Mon–Fri, 08:00–16:00). Priority 24-hour service available for fleet customers under a service agreement.
- Do you offer a warranty on BMS repairs?
- Yes — 6-month warranty on parts and labour as standard, 12 months for service agreement customers.