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High-Voltage Vehicle Research Tips: GM BEV Low-Voltage Battery Disconnection
I-CAR · August 28, 2025 · General Motors
Summary
This article outlines critical safety precautions for disconnecting the 12V low-voltage battery on General Motors (GM) battery electric vehicles (BEVs). It highlights GM's Battery Maintenance Mode, which can automatically energize 12V battery cables to charge the low-voltage system even when the ignition is off. Technicians must verify this mode is inactive to prevent electrical shock or burns during disconnection.
What to do on the job
Test the 12V battery voltage with a digital multimeter before disconnecting any cables; if the reading is 13.5V or higher, wait for the Battery Maintenance Mode to deactivate before proceeding.
How to use it
Incorporate this document into estimates and supplements to justify the necessary diagnostic time for testing the 12V battery voltage prior to disconnection. It also supports billing for potential standby/wait time (up to 2 hours) required for the Battery Maintenance Mode to safely deactivate, ensuring technician safety and compliance with GM's OEM guidelines.
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