Balance-of-system thermal failure
A degraded cooling or HVAC system silently ageing the whole battery.
Balance-of-system (BoS) thermal failure is degradation in a BESS’s cooling, HVAC, or thermal-management hardware — not the cells themselves — that lets pack temperature drift above optimal. Because it sits outside the cell-level data a BMS watches, it is largely invisible to standard monitoring, yet sustained operation ~10°C hot roughly doubles cell ageing. It is the archetypal "BMS isn’t enough" fault.
Symptoms
- Average pack temperature trends upward over weeks with no change in dispatch.
- Widening temperature spread between modules served by the same cooling loop.
- Cooling/HVAC drawing more auxiliary power for the same thermal duty.
SCADA signatures
- Module temperatures rising relative to ambient at constant C-rate.
- Auxiliary (HVAC) load climbing as a share of throughput — the same signal that erodes round-trip efficiency.
- Thermal gradient across the enclosure exceeding the OEM’s allowed spread.
Root cause
A failing or fouled cooling system: blocked filters, low coolant, a degrading chiller/compressor, or fan wear. None of it shows in cell voltages, so a BMS watching cells assumes all is well while the balance-of-system quietly bakes the pack. Industry inspections find thermal-management defects in a meaningful share of deployed BESS.
Financial impact
On a multi-million-euro asset, sustained operation ~10°C above optimal roughly doubles the lithium-ion ageing rate — consuming years of warranty life and pulling forward augmentation spend. The cooling repair is cheap; the degradation it causes if missed is not.
How NuraVolt detects it
NuraVolt models expected pack temperature from ambient, dispatch, and C-rate, then flags the residual when actual temperature runs hot — catching cooling degradation as a balance-of-system anomaly the BMS cannot see, and linking it to the capacity-fade and RTE it will otherwise cause.
Frequently asked questions
See also
Cumulative high-temperature exposure that accelerates battery degradation.
Loss of usable battery capacity as State of Health declines toward warranty limits.
Falling round-trip efficiency as internal resistance rises.
The capacity that BoS heat quietly erodes.
See this on your own plants
NuraVolt turns your SCADA and BMS data into early fault detection, degradation-aware BESS analytics, and audit-ready reporting. A fixed-scope audit shows you what we’d find on your portfolio.