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Hi This morning was the first cold morning in Northern Georgia. My Volt displayed 29 deg F. ERDTT did not happen, as this happens at 25 F on my 2011 Volt. I often monitor 12V battery voltage on my morning drive with my simple OBD scanner device. Normally when I first turn the car on voltage is 14.5, this lasts about 5 minuts then drops to 12.7 (headlights off) or 13.5 (headlights on).

This morning the voltage stayed at 14.8-15.2 volts for the entire drive. I even left the car "running" for another 15 minutes in my work parking lot. When I came back I checked the volts with a multimeater on the battery terminals and the voltage was still 15.3V. What is going on? Will the Volt set the charging voltage this high when the air tempature is low? Maybe the reasoning is with higher voltages the heated seats will get hotter and more energy for wipers, etc. Thanks

-Eric
 

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You likely had more 12V loads than normal, for one reason or another. The DC-DC converter in the Volt has a "negative resistance" built in, which basically increases the voltage as load increases. Higher voltage implies a higher load on the 12V system.
 

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If I remember correctly, the 2011 models do not monitor the 12 volt battery after the HV battery has been fully charged. It may be that your 12v battery was a little lower in power due to the colder temps and once you turned on your car, the 12v system was working harder to recharge the 12v battery. Or it could be just cold weather equals more 12v power needed. How old is your 12v battery? It might be showing its age.
 
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