Does anybody have problems with batteries draining over time when not driven? I have an 89 and I don’t get to drive her much, the vette sits in the garage under a cover for 1, 2 or sometimes 3 weeks at a time. I was having trouble with the last battery due to, basically old age. I replaced it with an Optima yellow top heavy duty battery. Because of the problems with the last one I was disconnecting the battery when parking up and reconnecting on the next drive. The car would start first turn of the key. The last couple of times I have left it connected. The first was about 2 weeks and It would not start motor would crank but you could tell the battery was low, I had to use my jump starter to start the car. After a long drive it seemed to OK, cranking fast an starting straight way. So I left it connected for another week and it did start first up but didn't seem as strong so I took the jump starter with me because I knew I had a short run before I would have start again and sure enough it would crank slower and I needed to add the jump starter to start the car. I recently say 6 months ago put a new alternator in. The vette seems ok if it driven for a bit and will start ok. Its only when I don’t drive it that I am having problems first up.

Doesn’t anyone have any info or experience with this kind of thing? I would expect the battery to drain over time but it’s supposed to be a heavy duty AGM battery? Is there a way to test if the battery is draining too quickly?

 

If you disconnect the negative cable and connect a meter set to measure amps between the cable and the battery terminal, key off you should get a maximum reading of 50 milliamps (.05 amps), any more and you may have a drain.. If I plan on leaving my vet without any run time for more than a couple of days, I use a battery tender..

 

my 89 had battery drain issues for years. Recently I was in the car, with it turned off and I felt the seat jolt and heard a noise. I have been lazy and haven't investigated the issue, i pulled the power seat/door lock fuse problem solved. Haven't had the issue since replacing the battery 5-6 weeks now. Chances this ins't your issue but same year ya never know.

 

Thanks for the help Ccrazor and Guno89... I guess I will see when I test the drain amps... I was thinking a while back I should get one of those bater tenders.

 

Don's forget to turn Off the under-hood lts before making the drain measurements.

 

AGM batteries will die a premature death if they're discharged too low.

Check for battery drains, as suggested earlier. I have heard of the seat(s) and the antenna causing an extra drain. Basically they get into a mode where they aren't quite all the way off.

 

If -any- of my cars are going to sit for a week (heaven forbid longer) I always disconnect the negative lead off the battery.

Even on cars with a fairly low drain. Better to be safe than sorry later.

 

You shouldn't be having a problem at 3 weeks with a new battery draining. Like someone else said, get a multimeter, set for measuring amps, then disconnect the negative lead. Put one lead of the multimeter on the negative lead cable and the positive lead of the multimeter on the negative post of the battery, measure you amps... should be between 30 to 50 mA.

Shorts are important to find, because heat is created by a short and...well...enough heat can cause a fire.

Anything over 50mA means a short so to find it, start pulling fuses until you see the mulitmeter drop down to the 30 to 50mA. The last fuse you pull will at least point you to the right circuit in the car.

 

I have a 90 MA drain on my battery right now..I have to start looking for the cause shortly. I also put my battery tender on if Im not driving it for awhile....WW

 

Thanks for the comments... Thats what I had in mind BA22. Does anybody know what the battery voltage should be when charged and in good health? Mine is 12.57 volts tested when connected, ignition off and I guess the bonnet lights would be on also.

 

Buddy of mine had a similar problem, when he didn't drive his '93 for 4 or 5 days the battery would drain. He had pulled the targa top off to make it easier to get in/out of the car while working on it (he's a big boy)...he said one night out in the garage after turning off the lights he saw some light coming from inside the car. Lights in BOTH visor vanity mirrors were on, even with the key off.

It's not supposed to work that way, but you never know....

 

From what I've read, a fully charged battery should be around 12.60 to 12.75..I think it might depend on which make battery you have....WW

 

A little more, QUOTE.. Normally a 12 Volt battery is fully charge with an at rest Voltage of around 12.7 (+/- depending on manufacturer's specs).

To get there, deep cycle batteries need to be taken up to 14.2 to 14.8 (again depending on the particular battery) Absorb Voltage and held there to complete the charge.

Then there's the Float Voltage which is a level that is maintained as long as possible to keep the system working well. This is usually around 13.8 Volts and can be as low as the resting Voltage. Again it depends on the battery maker's numbers.

So it all depends on the particular battery. And how accurate your meter is. And the temperature. And the phase of the moon.