BYD Atto 3 12V auxiliary battery drain — software fix
The 12V lead-acid auxiliary battery drains overnight leaving the vehicle unable to start the next morning. This is caused by certain vehicle systems remaining active after the vehicle is locked. BYD issued a software OTA update that significantly reduces the parasitic drain. Ensure the vehicle has received all available software updates. As a temporary measure, a battery conditioner/trickle charger connected overnight prevents the drain.
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⚠️ Wrong Diagnosis?
No commonly reported misdiagnoses for this fault yet. If you have replaced a part that did not fix this BYD Atto 3 2022 problem, submit a wrong diagnosis report — it helps other drivers avoid the same costly mistake.
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