This is happened at least 4 times now.

On road trips, I've taken breaks to sleep in the back. I've got a super nice setup, with a custom mattress and shades. So it's actually sometimes more ideal to nap in the 4runner undisturbed than at home.

Sometimes, I can't for the life of me get it --> the battery will be completely drained after being in the 4runner for as little as 2-4 hours, and overnight camping. I lock the door, and nothing is running. No stereo / no lights. Nothing.

I go out to start the car, and the engine doesn't turn. It only happens sometimes, and when I'm taking a nap (lol) with the keys inside.

Luckily, I keep a schnazzy battery pack in the back that works every time.

My concern is that I have NO IDEA what is draining the battery. I don't want this to happen in the wild, especially where my backup battery pack might not work as well.

Anyone have this same problem?

it sounds like you need a new battery, have you actually checked with an ammeter that you have something draining it?

how old is it, what's the resting voltage?

this has happened to me before too. i was sleepign in the back and at about 1am my car alarm started going off. managed to stop it, btu then i noticed the engine start button was glowing orange... the alarm seemed to be the cars way of telling me the battery was out of juice. ended up having to walk a couple of miles in 20 degree weather to meet a AAA guy to come jump me in the woods. car started right back up. let it run for 30 min and went back to sleep. really dont know what caused it and i havent had an issue with the battery since

You went out by yourself in the middle of nowhere, 20 degree weather without a portable $60 battery charger?

with fire, firearms, food, beer, and a friend w/ me... not concerned.

Obviously step one is to have the battery checked.

Do you have push to start? Maybe the keyless entry signal or something is draining the battery.

When you aren't sleeping in the back of the 4runner and it's normally parked this doesn't happen?

Can't speak to why this happened. Did the exterior lights stay on for some reason after you locked the truck? This happens to me if I use the remote starter and lock the truck without first opening and closing the drivers door.

I will say that the OEM battery has to be undersized or junk. I've killed it a few times after having the radio and nothing else on for maybe 20 minutes. Since day one, on cold days, it sounds like a half-dead battery starting the engine. I'm unreasonably excited for a reason to replace it with something with a higher capacity.

I was thinking the same thing. But that's a lot of juice to loose in a couple hours.

Battery is stock.

It's about 12.1 V, resting.

Someone mentioned that it might be the sensor in the key. I don't have push start...have an sr5...so I'm not sure.

It's a mystery for sure, but at 90k miles, it's probably about time to replace the battery anyway. It would be a huge hassle to be on a trail and not be able to start the truck cause of a bad battery!

I think you're right. It's something to do with the oem battery. We're talking like 2 hours tops inside. It must be something to do with the key. And batteries shouldn't drain that fast.

My OEM battery only lasted about 3 years. Not a very long life for a new battery. I noticed it would be dead after a few days of not driving.

Do the puddle lamps come on as you approach? I can't remember if mine do or not. If so they may stay on when you're in the car. Or the vehicle might be recognizing some sort of signal from the key that is energizing a circuit somehwere for the ignition that's creating some drain. Shouldn't be much though.

Resting should be more like 12.7-12.8. But that's after a day or so. When you shut off the ignition it should be reading something like 13.4v initially before it drops. As an example my camp trailer has 2 12v batteries. I just checked them. They are at 12.5 volts and haven't been on a charger since October. And they are outside in freezing temps. So 12.1 probably means you've got a bad battery.

90k miles on the original battery. Damn you got lucky there unless you drive 30k a year I'm assuming its at last 5 years old.

THanks for the info! I'll be shopping around for a new battery. It'll definitely be an upgrade as soon as more money pours in. Life is expensive.

LOL. It's a 2014. So I guess I've been lucky. Probably put on about 20k / year. Lot's a road trips cross country!