New Battery Went Dead Twice in One Month Overnight

[mweiss]

We've had our '06 Explorer XLT since 2008. We're on our second new battery since buying it off lease. No after market car alarms installed.

Last summer, I realized the battery we'd installed in 2008 was getting tired, so I bought a new one and installed it. It was fine until about a month ago.

My wife uses it as a daily driver to get to work. A few weeks ago, the battery drained completely overnight. We suspected a dash cam that she left plugged into the cigarette lighter socket. I recharged the battery and the thing was fine for a few weeks. After charging, I started the engine and checked that the voltage had increased from 12 volts to 14.5 volts, indicating a proper functioning alternator. So the battery IS charging while the engine is operating.

This week, after using the vehicle with no trouble starting the day before, the battery was dead again. Just the solenoid chattering, no crank.
I took out my meter and measured the voltage at the battery terminals. It was 11.7 volts. However, when the starter solenoid attempted to engage, the voltage dropped to below 5 volts. I charged the battery, and checked for no devices plugged into any lighter sockets.

The pattern is random. Plenty of cranking juice for a couple of weeks, then one day, after just a few hours sitting, battery is dead.

Before I chalk it up to a defective battery and go for an exchange, just want to get some input here as to whether there are issues with random parasitic loads placed on the battery due to aging vehicle electronics causing an intermittent problem.

 

[Rcflyer330]

Well to start you need to do a parasitic draw test. The problem is catching it if there is one. For example it could be something like this video by pine hollow auto Diagnostics on youtube


Either way you will probally need a new battery or at least get it checked before you start diagnosing.

 

[Explorer_PL]

Looks like you know what you are doing. For a moment bad grounds or bad starter crossed my mind ........
Time to unplug the fuses.
Remember, on these Fords, it takes about 15-20 minutes for all the circuits to go to sleep. Any time you touch the door or anything, start over. You can lock the latch on the driver door to mimic it being closed while the door is open so you can go in and put without waking up the car.

 

[LorenzoGarbanzo]

My dash cam kills the battery every time since it's been cold outside. Once i started unplugging it when I get home, no more trouble. Sounds like you've already figured that out but you'll just have to check the circuits for draw from the fuse box like suggested to narrow it down. I'm learning the wiring gets kinda brittle in these year trucks and don't take stress that well so it's possible something shorted.

 

[mweiss]

The odd thing that makes me think this is something intermittent is the fact that it will go for weeks without draining the battery, and then one random evening, it will drain to almost completely dead overnight. I was unable to find any phantom load responsible, at least nothing reliably there. That's why I'm seeking out crowd-gathered data to see whether there is a known intermittent issue. For example, with my Silverado pickup, there's a known issue with "whiskers" growing between IC pins on the dash cluster display board, which gradually worsen to the point where battery drain in a few days occurs. Doesn't seem to be anything like that on this Ford, but just citing an example that many people reported over the years. So I thought there might be a similar situation going on here, where something decides not to shut down properly once a month or so, causing battery to drain to zero in just a few hours.