BigRed85

I went to take my '85 out of the garage and the battery was dead. By this I mean completely dead as if I left something on. Completely and totally dead. No lights, no clicks, no nothing. In the past, with other cars, I've left the lights on or left the key on in a back up car and left the radio on (I know). This isn't the case here. Is there anything else that might be left on that would drain the battery so completely?

antfarmer2

Disconnect the battery and bring it to a full charge. Then hook it up and see what is shining.

BigRed85

🤔 Already have it charged up. I didn't notice anything. Thought there might be something that commonly did this.

antfarmer2

There are a lot of good folks in here. But do not believe we can guess what you are going to do. might take it in and get a load test. Might just be saying goodbye.

Sid.123

What you need is an amp meter to check for current drain..Your looking for a max of about 0.3 amps with everything off

BigRed85

Thanks, I'll give it a try.

CA1992C4

How old is your battery?

Bringing your battery it to a full charge and then load testing it will tell you if your battery is still good.

BigRed85

It's about six weeks old.

antfarmer2

If it does it again take it for a load test. They can be bad new but is under warranty.

CA1992C4

The battery could be bad, but I'd put money on you left a light on somewhere.

RICHARD TILL

How long had it sat?

BigRed85

Three days

BigRed85

That's what I'm hoping

divotdug

Check it again tomorrow morning. if all is well something most likely left on.

If dead again, don't rule out a bad alternator diode.

3798j

Agree....this was my '85's problem (years ago). Drains a fully charged battery fast.

ddahlgren

This should show up in a current draw test I would think and will keep in mind as one of the easiest checks right off the bat.

I am a bit curious about how long the car can sit without use with a 0.3 amp draw and did some calcs with .3 ampsX24 hoursX30 days and came up with 216 amp hours and assuming a quite dead battery at that point.

BigRed85

The car started this morning. It had not been started in three days when the battery was dead, but was okay after one day at least. I didn't find anything that might have been left on. I'll just continue to monitor.

ddahlgren

I have been playing the same game for the past 6 months and have not driven the car as have no faith it will get me home until sorted out. Tomorrow will get some new battery bolts and a new DVM as have lost faith in mine on the voltage scale. It is 15 years old and served me well at a zillion race tracks and dyno sessions. I am guessing the selector switches just corroded and wore out. I charged the batter for 3 hours at 15 amps and 2 hours at 2 amps and the charge light never came on green for charged on the 2 amp scale. I did have the battery hooked up and while working in the shop will charge again at 2 amps battery disconnected until green charged light comes on and test from there. I do have faith in the amp scale in the meter I have as does not hunt or read silly numbers. I did do a quick draw test and got .5A at first for 4 or 5 seconds then settled at 0.015 to 0.02A so 15 to 20 ma. and should easily stay good enough to start in 2 months, 1 at least I would think. After fully charged with battery disconnected will check self discharge rate by leaving disconnected and read voltage at the battery to see how fast it goes down no load. If it loses 1 volt a week will never make it to 8 weeks. I would think at that point the battery is NG.