Battery voltage very low warning and unexpected shutdown

If your BMS displays a Battery Voltage Very Low warning with a 90-second countdown, or the system shuts down unexpectedly, this article explains the cause and how to respond.

The 90-second countdown

When battery voltage drops below 44.8VDC (0% SoC), the BMS display triggers a Battery Voltage Very Low warning and begins a 90-second countdown. If a positive charge current begins before the countdown reaches zero, the system will not shut down. If no charge arrives, the battery will shut down to protect itself from over-discharge.

Charging displays as a negative amp value on the BMS screen. If you see a negative value, the system is receiving charge and should stabilise.

Immediate steps when the warning appears

Connect to shore power immediately if available — plug in the 240V 15A supply lead and ensure the Main Switch Grid Supply is ON.
Ensure solar panels are receiving direct sunlight and the PV Array DC Isolator is switched ON.
If neither is immediately available, reduce all 240V and 12V loads to minimum to slow battery drain and extend the countdown window.

If the system shuts down

Connect to a charge source (shore power or ensure strong solar conditions).
Restart the system following the standard startup procedure: Battery Isolator key to ON, hold Push to Power for 7 seconds.
Once restarted, confirm a negative amp reading is showing on the BMS indicating the battery is receiving charge.
Do not continue to discharge from the battery once this warning has been triggered, as this further reduces the limited remaining capacity.

False shutdown triggers

Some battery units have a firmware calibration issue that causes this warning to appear incorrectly — typically as a one-off event where the system shuts down and then immediately shows 100% SoC and 58V on restart. If this happens to you, note your battery serial number (on the chassis label beneath the van) and contact OzX Corp support. A battery firmware update is available that permanently resolves false shutdown triggers.

State of charge calibration

If the SoC percentage is drifting significantly from the voltage reference table, a full calibration cycle is recommended. Charge the battery to 58VDC, then discharge fully using appliances until the battery shuts down, then recharge fully to 58VDC again. This recalibrates the SoC gauge. Only perform this when you have access to shore power.

Need help? Contact OzX Corp support: 0493 980 869 | support@ozxcorp.com