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Posts: 2774
Joined: Mon Nov 22, 2010 6:47 pm
Delivery Date: 12 Jun 2011
Location: Phoenix, AZ

Re: Should I do it? '14 SL w/36K for $11.5K?

Sat Nov 23, 2019 9:35 pm

LeftieBiker wrote:
Wed Nov 20, 2019 2:59 pm
I also turned to car of e then plugged in to charge the car, and a few seconds after I saw voltage go up to 14-15V for about a minute or so then back to rest. So that leads me to believe the car is capable is charging the 12 V battery when plugged in, though when and how often I don’t know. I was just making sure the car was even charging the battery.

The issue is when you leave the car plugged in but not charging for a long time, either because charging has finished or because a timer has been set that won't allow charging to start for many hours. Also, the charge delivered to the 12 volt battery while the main one charges is enough to maintain the existing charge of the 12 volt battery, but is not sufficient to recharge it.
To correct some misinformation: The car charges the 12V battery while the traction battery is charging at the same rate as when the car is being driven. When the traction battery is not actually charging, the DC-DC converter is not active so the 12V battery will slowly discharge. There is more residual load on the 12V battery when the car is plugged in and not charging than when unplugged. This means the 12V battery will be fully charged when the traction battery finishes charging, but will slowly discharge if the car is not unplugged. Also, the car will periodically turn on the DC-DC converter to charge the 12V battery from the traction battery when parked for extended time if it is not plugged in. The DC-DC converter output is about 14 to 15 volts until the current flowing into the 12V battery drops below a threshold; then the output drops to float charge at about 13 volts.
Silver LEAF 2011 SL rear ended (totaled) by in-attentive driver 1/4/2015 at 50,422 miles
Silver LEAF 2015 SL purchased 2/7/2015; traded 8/10/2019 at 82,436 miles
White LEAF 2019 SL Plus purchased 8/10/2019

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