If a battery is missing, failed or having a communication error, replace the battery.
If a battery is failed, replace the battery.
If a battery is charging, this error should go away when the battery is charged.
If a battery is too hot, the system can be started after it has cooled.
If running on a single power supply with low input power (110 V AC), "low voltage" will be seen in the extra data. If this is the case, the failed or missing power supply should be replaced. This will only happen if a single power supply is running with input power that is too low.