jumpstart 12V battery

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OldMortality

New member
Joined
Jun 27, 2022
Messages
2
I have a 2013 Leaf, awesome car.

I had been sitting in the car today, in a parking lot, with the lights on, for about half an hour. Then the car would not start. Lots of lights flashing and beeping, but not starting.
The AA man started it with one of these handheld devices. I didn't like this so much, but I didn't have very many options.

The car started, but the main battery (the one that drives the car) showed empty, and the turtle showed. The battery had been at over 50%.
The car and I limped to the fast charger, followed by the AA man. The fast charger said it started charging at 52%, and then I charged to 78%. Then I drove home without further events, arriving with the battery at 60%.

I thought it very strange that the fast charger said the battery was at 52%, which was probably correct, but the car would not go.

Does anyone have an explanation for this, and is this something I should be worried about?
 
Welcome to the forum. When the Leaf's 12 volt accessory battery gets very low, or dies, that can produce any number of false error codes and instrument glitches. To avoid that happening again, leave the car in "Ready" mode, meaning ready to drive and with the yellow-green icon of a car illuminated on the dashboard. In that mode, the car provides the power for all accessories from the main battery, preserving the charge in the little 12 volt battery. There is no harm in using only Ready mode, because the drive motor doesn't turn or "idle." Accessory and Off mode are both not a good idea for using the lights or accessories.
 
OldMortality said:
I had been sitting in the car today, in a parking lot, with the lights on, for about half an hour. Then the car would not start. Lots of lights flashing and beeping, but not starting.
Morale of the story: replace your 12v battery. Plenty of threads on options (see sig for mine).
 
Thank you for the replies.

I wasn't surprised that the 12V had gone flat after leaving the lights on, but I did think it very strange that the main battery had gone from 52% to zero, and I had the turtle, and the fast charger nevertheless said charging started at 52%. It was as if there was 52% in the battery, but the car couldn't access it. Is there any explanation for that?
 
OldMortality said:
Thank you for the replies.

I wasn't surprised that the 12V had gone flat after leaving the lights on, but I did think it very strange that the main battery had gone from 52% to zero, and I had the turtle, and the fast charger nevertheless said charging started at 52%. It was as if there was 52% in the battery, but the car couldn't access it. Is there any explanation for that?

When the 12 volt system voltage is low, there can be any number of false error codes. Given that, I'm not especially surprised at the wrong main battery reading. You could have an issue with bad cells, but unless that problem recurs when the 12 volt battery is fine, I'd disregard it.
 
An interesting sequence of events. One solution of being stranded by a failed 12 volt battery is to have a small lithium based "starter" battery in the trunk. After having such battery issues in my 2012, I have kept one ever since - just check it every so often for charge level. BTW, I've used it to start my gasoline emergency generator on occasion!

If you decide to set up LeaSpy Pro, it would be interesting to me what your traction battery condition readings are - just to check if you might have "bad" cell(s), or some other more serious issue that caused such a unusual situation - and might keep from further issues.
 
OldMortality said:
Thank you for the replies.

I wasn't surprised that the 12V had gone flat after leaving the lights on, but I did think it very strange that the main battery had gone from 52% to zero, and I had the turtle, and the fast charger nevertheless said charging started at 52%. It was as if there was 52% in the battery, but the car couldn't access it. Is there any explanation for that?

Really, 30 minutes of headlights shouldn't run the 12V flat. That's an indication that the 12V battery was really quite weak. Even weaker now that it's been run all the way down. When you charge the main battery, the 12V is getting charged too, so by the end of that it had enough voltage to sustain normal driving. I'd still consider it suspect though. You can get it load tested to verify, but if it's the original 2013 battery I wouldn't bother; I'd just replace it.
 
^^^+1
And even if the battery is a replacement and approaching 5yrs old, I'd seriously think of just replacing it. That or invest ~$50 in a decent portable battery jump starter and keep in the car for when it inevitably dies or leaves you stranded.
 
When you charge the main battery, the 12V is getting charged too, so by the end of that it had enough voltage to sustain normal driving.

Nubo knows this, but I want to clarify for the OP: the 12 volt battery gets PARTIALLY recharged when the main pack is charged. It doesn't get anywhere near fully recharged if it's low.
 
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