Snlj wrote:Hi Everybody,
Looks like this thread is due for a bump, which I may as well provide with my little story of dead 12V batteries.
A week into owning our 2013 SL, my wife arrived at the car after work to find it completely dead. No locks, no lights, no anything. A jump started everything up just fine. The traction battery was somewhere around 20% charged at the time.
The next week I brought it into the dealer and had them test the battery. It came back a little weak, so I had them replace it with a new one.
One week later, I came out to the new battery dead just like the first time. The traction battery was similarly at around 20%.
Neither time was the car charging, in accessory mode, lights left on, OBDII port being used, nor key in the car. The dealer has it right now, and is going to keep it overnight to test it when it's asleep. They did mention that there were no error codes when they checked.
The suggestion from the tech was that perhaps the short daily drives of a couple of miles or so were not enough to charge back up the 12V during operation. This seems a little wrong, and wanted to know what anybody thinks of this explanation. We've been charging once a week at L2, driving in either 2-3 mile or 10-20 mile spurts, with the 12V turning up dead two times out of two just before recharging.
This is a stupid problem to have. Can anyone help? I'd like to at least have other suggestions/questions for the dealership when I talk to them again tomorrow.
The 12v battery has a constant drain on it. Not a large one, but a constant one, as do all modern cars loaded with computers. The 12v battery is charged whenever the traction battery is charged. It is also topped off when the car is in run mode. The Leaf charging algorithm is not the best, and driving many short trips and only charging once a week work against you. The tech may not understand why, but he is not wrong.
Since you have a 2013, set the charge timer for 80% and charge at least every other day. Charge it to 100%, at least once a month (I would suggest every two weeks), to keep the cells balanced on the traction battery. Lithium batteries don't do well with constant low or high charge levels. It is better for the battery to have a 10 minute charge cycle every night that brings it up to 80%, than it is to let the level get low and only charge once a week.
It is also possible you have something failing, that is drawing a higher load than it should. One user reported an ABS unit that started having a constant draw on the 12v system that never stopped, even when the car was off. If you have not upgraded your telematics unit, it could also be causing an excess drain trying to connect to a network that is no longer active.