RedLS

Hello Everyone, I'm new to the forums and I am hoping to get some help regarding a battery drain issue.

A brief history of the car:
It is my wife's car and it has been sitting for the past year and a half. I would occasionally start it up every two months or so and let it run with maybe a quick drive to the corner store. I would have to jump it during these start ups and I never thought twice about it since it was sitting for 60+ days in between. The car is completely stock other than some performance tires and an alternator that was replaced in 2018.

Current problems:
I have to take the car out of mothballs and get it ready for my wife to use as a daily driver (she was driving my truck but since the new job doesn't provide a company truck I need to take the F150 back for work). I jumped the car and took it for a drive around town and on the interstate for about an hour. The car ran/drove like a dream even after sitting that long.

When I parked the car, I figured I had built up enough of a charge to safely shut it down. After about 30-45 minutes I came back to the car and the battery was completely dead and I couldn't jump it again. I hooked up the battery charger (leads still attached to the vehicle) and I heard something (a clunk almost) on the passenger side of the engine compartment engage/disengage and it would trip my battery charger. I disconnected the battery from the vehicle and gave it a full charge overnight. The next day I started her up and went to go have the battery/alternator checked at the auto store. Both passed.

The only thing I can think of is that there is some sort of drain on the system. I keep going back to the part where it was tripping my battery charger while connected to the vehicle.

Any thoughts on how to diagnose the issue would be greatly appreciated. I own a multimeter but I am a novice at electrical systems.

Thanks!

aptoslexus

My guess is your battery is cooked, despite what the auto store tester says. It hasn't been properly maintained for an extended period of time and it's probably done for. Charge it up, put it in the car, put a meter on it and start turning things on. If the voltage starts dropping like a stone, you need a new one.

RedLS

Tried that and the voltage didn't really drop below 11.5 Volts even with the AC, Lights, and Radio on. I ended up taking the battery out and bought a new one yesterday afternoon. Put the new one in last night and started the car once to make sure it would turn over. Went to move the car this morning and the brand new battery was completely dead, dash lights won't even turn on.

I'm at a loss.

Thanks

Yamae

https://www.clublexus.com/forums/ls-...s-dying-2.html
You can find the root cause of the parasitic drain checking all fuses. You can check it without removing fuses if you have a good multi-meter.

aptoslexus

RedLS

I tried the method shown in the BBB video, it was pretty informative. I had a 10.44 amp draw. I pulled all of the smaller fuses under the hood and there was no change. I couldn't get the larger 40, 50, and 80 amp fuses or relays out, it felt like I was going to break them.

With such a large current draw, I'm thinking that the larger systems are where the drain is???


Thanks.

Yamae

Why didn't you check fuses under the dash?

RedLS

I should've added that I plan on doing that tomorrow once I can get another pair of hands. I didn't feel good about leaving the multi-meter clamped to the terminal (leads were getting pretty hot). I was just wondering if you guys knew what systems could be drawing that kind of power? Every other instructional or post I see only has a drain of 3-4 amps max.

Thanks,

Yamae

Your multimeter is good enough to check the very low voltages setting it 200mV range and simply apply 2 leads just to 2 small metal terminals at the top of the fuse. Read the value. If a 10A current is going through a 20A fuse, you will read around 100mV or so. For an example this photo shows that you can read 3.26mV when the fuse is passing through 365.4mA.

As far as I have checked, Toyota's genuine fuse of 10A has the internal resistance about 0.01 ohms. In case of 20A, 0.005 ohms. That's why you would read some voltages only applying your multimeter's 2 leads to the top of the very fuse without removing it.