2013 Dead 12V Battery

I have a 2013 Leaf that has developed an issue. If I don't drive the car for a few days, the 12v battery (not the main pack) drains completely. I take it out and put it on my trickle charger and it works great. As long as I drive the car every day or every other day it works fine.

The 12v is 6 months old, and I've twice taken it to have it checked and it comes back perfect.

This leaves me to believe that something is draining the battery when I'm not using it. Has anyone else had this happen?

Edit by moderator: added "12V" to the subject

Do you leave the car plugged in when not charging? That will kill the 12 volt battery. If not, then you have a relay sticking open somewhere, aka a "vampire drain."

There are several threads that discuss this issue on 2013 models, but no definitive answers as to cause. The telematics unit (SL or SV only) is a possibility if it is trying to transmit data and keeps car modules from going into low-power (sleep) mode. I routinely park for up to a month at a time and had no issues with 2011 (except once when I left the Bluetooth adapter plugged into the OBDII port and an Android device running Leaf Spy on the passenger seat) or 2015 (except once when the first-generation upgraded telematics unit failed to sleep) and have had no issues so far with the 2019. Ordinarily, the car periodically turns on the main contactor and DC-DC converter to charge the 12-volt battery. In my two cases, I believe the active modules caused much higher standby current draw from the 12-volt battery and also interfered with the automatic charging algorithm so I had to use a 12-volt booster battery to "jump start" the LEAFs. The 12-volt batteries were each recharged by the time I got home after driving about 30 miles.

Howdy jeff,

If this issue continues to drain your aux battery, then you might have to do some troubleshooting to get to the culprit.

Would you have access to a voltmeter and clamp-on current probe? If so then you would clamp onto one of the terminal cables and monitor the current at the aux, while also monitoring the voltage. With everything OFF and doors closed, etc. you could measure how large is the drain current. Typically you would only see ~20 to 40 mA. If more than that you would start pulling fuses one at a time to find the circuit with the load.

If not, then you will need to find a good electrical tech/mechanic to perform this testing.

Does your trickle charger run the voltage up to 14.4 VDC? How was the battery tested and determined to be good? A lead acid battery can suffer permanent damage in as little as 3 days stored in a discharged state due to the sulfation of the plates. Only a full voltage charge can attempt to desulfate, usually trickle chargers don't cut it.

Good luck hope you find it.

jeffwash said:

I have a 2013 Leaf that has developed an issue. If I don't drive the car for a few days, the 12v battery (not the main pack) drains completely. I take it out and put it on my trickle charger and it works great. As long as I drive the car every day or every other day it works fine.

The 12v is 6 months old, and I've twice taken it to have it checked and it comes back perfect.

This leaves me to believe that something is draining the battery when I'm not using it. Has anyone else had this happen?

Click to expand...

Oh course the car has a load on the battery all the time. Your doors open when you push the button, right? Your radio stations are there every morning, etc.


Where are you located?

Do you park in a garage?

What trim do you have?

Thanks for the great suggestions all!

I decided to take the 12v to a different location in the same chain where I bought it to have someone else test it. They found a bad cell and replaced it for free. Hopefully this was the issue and fixes it. I'm going on a business trip next week, so that will give it a good test.

-Jeff