Replacement 12 Volt Battery Failure (Dead Battery)

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Christopher

New member
Joined
Apr 28, 2016
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2
The dealer replaced the 12Volt battery at 19,000 miles following a failure to wakeup the system. The new battery failed after two days of light use. I suspect the overnight charge cycle is leaving a circuit open and draining the 12Volt. The dealer Customer Service Reps are friendly, but don't convey an understanding of this vehicle and how it operates.
 
Pretty sure the 12v is getting charged anytime the vehicle is charging or in ready mode to drive.
Maybe the dealer just gave you a bad battery to warranty it and clear the shelf.
Or maybe this is just the symptom of something else wrong. Keep us posted.

Lots of posts of the 12v battery going bad around 36 months.
 
My wife used the vanity mirror in the passenger seat last night and its light was on the whole time we were at dinner. Since I only had a one mile drive home which would be insufficient to recharge the 12V, I left the car on a tender overnight.

If there is a problem with the DC/DC converter, it could also cause the OP's problem.
 
The dealer has performed a parasitic draw test to identify things like interior lights, left in an ON position. The initial test was negative, so they kept it overnight. Hopefully, they plugged it in for a charge cycle to see if that triggers the problem. I may have to set my alarm to get up at 3am, to see if something is operating in the vehicle during or after a charge cycle.
 
There is always a load on the 12 V battery. The Battery Management System (BMS) operates 24/7.

I would have them tell you how many amps the battery is pulling while turned off... it won't be zero. And then simply measure the battery voltage when the car is on and it should be around 13.8 to 14.2 volts.

Finally, measure the battery resting voltage after it's been disconnected and sitting for at least an hour or so. It should measure 12.7 V minimum.

These are all extremely simple and straightforward tests that anybody can do with basic test equipment and just a few minutes of time.

Just provide us with the data and I think we can help you:

1) Amps while vehicle is off (will be greater than zero)

2) Voltage with vehicle ON / READY (should be 13.5 min)

3) Voltage with vehicle OFF for an hour with battery disconnected (should be 12.7 min)
 
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