85WHITEZ51

My battery won't hold the cranking amp charge for longer than a week. If I let my car sit for a week it won't start but all the gauges, lights, and radio come on just like they do with a full battery. I have replace the battery cables, the battery, and the alt. recently, so I don't think it is one of these things. I am stumped as to what the problem could be especially since it is only the cranking amp that are failing and everything else works fine. Please help. Don't just tell me to drive it more because I can only get to it once a week at the most untill college is out. Thanks for any help given.

bogus

you might have a dead short... I know someone here can help with diagnosis on that vintage.

85WHITEZ51

Whats a dead short? :bb

GlockLT4

I think it means a plate or two are touching inside.

scorp508

What make/model battery is it? Perhaps a deep cycle battery would be better suited for you if you are driving it that little? (Shouldn't need it for a week though!)

K87ZZ4

If it's not a short in the battery, it could be some kind of short somewhere in the electrical system that is slowly draining the battery of enough energy to run the starter. If that's the case... good luck, those can be difficult to track down. :sad:

PeteL

I would be thinking in one of two directions:

1.) Battery won't hold a charge due to internal problems.

2.) Corvette electrical system is draining the battery in a week (which it should not).

Hopefully the guru of all things electrical, jfb will be along shortly. In the meantime, this is what I would do.

Fully charge the battery, this may take a day or two on a low current automatic charger. Let the battery sit for a couple of hours after charging and then use a decent DVM to measure the voltage of the battery, it should be around 12.6V or so. If in the 11's and your really did charge for a couple of days then the battery is probably a gonner.

If the battery seems to charge, then put it back in the car and hook up the positive cable. Use a good current meter to measure the current (in Amps) between the negative battery post and the negative cable. Red wire (or +) goes to the Neg bat cable. Use the highest current scale to start. Current should not exceed 30 mA or 0.03A or thereabouts.

Good Luck,

Pete

rmurcek

If you don't have a meter, or don't want to risk blowing one out with an unexpectedly high current, use a 12V bulb. A courtesy light kind of bulb, for instance, should light really dimly if at all on the 30 milliamps mentioned in the previous post. (This would be with one of the battery cables removed, and the bulb then connected from that cable to the post. I guess this should be done on the negative cable for safety reasons.)

The suggested battery test comes first, though, no point in looking for a car problem if the battery's bad!

Be especially suspicious of non-factory stuff. I had a problem with an aftermarket alarm where a certain sequence of events would cause the alarm system to suck 5 amps, which would occasionally kill the battery. Almost went nuts.

85WHITEZ51

This is the third battery I have had in one year. They are all interstate batery's which my local corvette shop put in for me. They said they are the best battery's out.

scorp508

Of course they did, they sell them. ;) I would definitely look for a drain while the key is off.

bogus

interstate and exide, ad nausem, are all made by the same factory!!!

your problem is something that is either on, or there is a short. meaning, that power is going to ground in some way. more than likely, you have something on.

I read a tech article about this in Corvette Fever several months ago... if I can find it...

GlockLT4

In my cars, those are easy to track down .. it usually ends up being something with the after market stereo amps ;)

jfb

I suspect excessive current being drawn by some circuit which discharges your good battery in a week (should take much longer than that). Disconnect the ground cable from the battery and put your ammeter between the battery post and the ground cable so you can measure the leakage. Start off with the ammeter on its highest range and after the courtesy lights go out, switch your ammeter to lower and lower full scale current until you can measure the leakage current. It should be under 20 milliamps. If not, then you need to find out which circuit is drawing current and shouldn't. Put the batt cable back on and open the fuse door. Remove one fuse at a time and put your ammeter across the fuse clips to measure the current in that circuit. Replace that fuse and go on to each one. If you do not find a circuit that measures the same as the current out of the battery, then you will have to start disconnecting the 8 or so fusible links under the bolt next to the battery ( the jumper cable bolt) and measure the leakage current in each of those links. If still not found, then let us know and I'll look at the remainder circuits that aren't fused or have no fusible link in them and advise you.
You can eliminate the battery by charging it up and disconnecting the ground cable for a week and replacing it and attempt a start. It should easily start. One other check I would make is to disconnect the large red wire on the alternator (be careful, it has 12 volts on it, best remove the batt ground, then replace the ground after measuring the current into the alternator) and measure the current with your ammeter with the ammeter probes between the red wire and the bolt on the alternator. Alternator diodes have a habit of breaking down and drawing current. Good luck.

85WHITEZ51

Thanks. It will be about a week till I can do that but I will let you know.

BrianCunningham

What's your voltage reading? Is it charging.


I've got problems starting mine.
Finally decided I've got a flat spot on my starter. :mad

BTW you can have a battery retailer, like SEAR's etc, do a full check on your charging/starting sytem.


[Modified by BrianCunningham, 3:39 PM 2/19/2002]

85WHITEZ51

It holds a charge of 14 volts while driving with my aftermarket stereo w\ amps, two auto meter gauges, heated O2, fans on. While at idle it may drop to 13 and with the headlights on it will drop down to about 13 also at idle but while driving no matter what it is at 14 volts. This reading comes from my auto meter gauge not the degi dash reading. The starter was checked last year when this first started to happen and everything was fine.