The Scan My Tesla android app shows the 12V battery voltage but only while the car is awake. When the car is awake, the DC-to-DC converter that charges the 12V battery is always active; likewise, when asleep, it is not active. The SMT app receives no data over the CAN bus when the car is asleep. Tesla must have a way to monitor the 12V AGM battery voltage while the car is sleeping otherwise how would they know when to wake up and top off the 12V battery? Since my car often stays awake for hours, it might simply wake up after X hours have transpired and not be monitoring the 12V voltage?
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buyehara
Member
Thanks for the insightful information rrolsbe, what about when the car is charging? I'm hoping when the main battery is being charged that DC-to-DC converter is active to charge the 12V battery.
If the car is actively charging it is awake. When the car is awake, the DC-to-DC converter supplies all power required by all the 12V subsystems such as pumps, computers, center display etc. It also supplies the power to top off the 12V AGM battery but if the approx 14.8 volt full charge level has been reached the current being sent to the battery should be very low.
buyehara
Member
Thanks, that's good to know. We keep the car charged to 80% on a daily basis so all indications point to possibly a defective battery. Hopefully this new battery should last awhile. Tesla was very good about covering 100% of the replacement, tow and servicing. They also replaced the chrome trim that was damaged as a result of the dying battery, no questions asked.
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