False Expectations???

CobraEd · #1 (**permalink**) 04-20-2005, 10:34 AM

I have a 95 Oldsmobile Aurora which was my wifes new car and is now our "spare" car.

The car started up and ran fine the last time we used it. that was between 3 and 3.5 months ago. The battery is now totally dead after sitting for that period. The things in the car that I can think of that are "always on" are:

Alarm
radio station memory
clock memory
remote entry reciever
Main engine computer (ECM)

Are these things enough to drain a good battery over three months or so? The battery is somewhat old, would a new battery maintain charge this long, or am I asking too much for any battery.

If I am expecting too much, I will get one of those solar chargers and leave it sitting on the dash.

WADDAYOUGUYSTHINK?????

Ed

rms427 · #2 (**permalink**) 04-20-2005, 11:06 AM

I have a 97 Toyota Supra and if I let the car sit for about 3 months the battery is dead (this is with a fairly new battery). I either make sure I drive the car about once per month or hook up a battery tender. The ZR-1 Corvette will also run the battery down within a few months if not driven. I think this is due to all the alarm etc. on the newer cars. I can leave the Cobra and 52 Chevy for a long time without running down the batteries.

Yetiman · #3 (**permalink**) 04-20-2005, 11:46 AM

Doesn't surprise me a all.

need4speed · #4 (**permalink**) 04-20-2005, 12:02 PM

Is the battery still good once it is charged? I have seen many a battery go bad with shorted cells after sitting with little use over long periods of time. If it is still good, then a trickle charger or solar charger would be a good idea. another alternative is to consider a gel cell which seems to hold up better over long periods of non-use.

CobraEd · #5 (**permalink**) 04-20-2005, 12:10 PM

I havn't had time to charge it or do anything with it yet. Maybe this weekend. I think, no matter what, I am going to get a solar trickle charger and leave it on the dash.

DonC · #6 (**permalink**) 04-20-2005, 01:50 PM

My battery manager will supply up to a 2A trickle charge if needed to maintain the battery state.
I've got an Optima in the little red car and it has a 44Amp/Hour rating. That means that it will supply 44 amps for an hour before becoming discharged.
The trick is to gain 2 pieces of information.
1. What is the amp/hr rating of your battery. That doesn't mean CCA or any of the other values that manufacturers and sales outlets throw around but the amp/hr rating. You may have to dig a little to find it.
2. What is the draw on the battery of those items that are "always on". With a chaged battery in place simply hook an ampmeter (radio shack cheapy works fine) in line with the positive cable of the battery between the + post and the cable end. You will probably get a value in miliamps - 0.0xx or 0.00x (thousandths of an amp)
Take the mA rating and divide it into the amp/hr rating of the battery and you'll know how long the always on static drain on the battery will take to deplete its charge.
In my case I have a 0.03A always on static drain on my battery and, at 44 amp/hr it will take 1466 hrs (61 days) to drain the battery.
DonC

clayfoushee · #7 (**permalink**) 04-20-2005, 10:14 PM

A $29 Battery Tender at any decent car store can solve all your problems.

phatry5 · #8 (**permalink**) 04-20-2005, 10:31 PM

Also, with it being drained all the way down may be a good thing. As long as your cells didn't reverse; it is good to drain it all the way before charging it so it doesn't develop a memeory.

302cobra · #9 (**permalink**) 04-20-2005, 10:53 PM

You can get, whats called, a Battery Stabilizer. Plug it into a wall socket and a special fitting that connects to your battery and it will keep your battery charged, over long periods of time.