battery keeps dying

[salazar44]

Hey guys. Im getting pretty frustrated! My battery keeps dying and I cant figure out why. I have taken my alternator in twice and they say its charging correctly.

its not like an overnight battery kill but more like a 30-40 start kill.

Any suggestions on how to diagnose this?

[jchav62]

Sounds like a short somewhere. One thing you can do is put a light tester on the negative side of the battery. I haven't done it in a while, but if I remember correctly if there is a short it will light up. Then start your search. Pull fuses and plugs one by one until the light on the tester shuts off. Once you find the circuit with the short you can find it and fix it. Good luck...

[salazar44]

but wouldnt that type of short typically drain the battery overnight? or soon after? This took about 3 weeks to drain. I think most of the drain took place from actually starting of the truck and running the headlights.

I will definately test your method though!

[jchav62]

You are probably right. Have you checked or replaced you voltage regulator?

[BigDaddyDave]

Mine was doing the same thing. I replaced both the battery and the alternator two different times,as well as the starter. After being towed home more times than i care to remember,i started checking all grounds. I found a bad ground under the front bumper,in the main harness. My truck was running off of the battery only,after it drained down it would not start again. Hope this helps

[TINKERDUKE]

An easy way to test if your alternator is charging is by starting the truck and disconnect the battery while its running- if the engine keeps running then your alternator is charging and if the engine cuts out then its not.
Test for a drain like mentioned before- disconnect the negative terminal from battery and wire a bulb by connecting one side to the negative battery wire and the other side to the negative battery post- if it lights up you have a drain somewhere!

[salazar44]

thanks guys. cant wait to try this when i get home! i hope its an easy fix!

Is it possible for wiring to be bad in the truck and kill the battery? because my previous battery was fairly new like 6 months old and they said it was bad.

[#169fan]

I have bought batteries before that went bad within a few months.Is it possible that you have a bad cell in your battery.I had the same thing happen about a month ago, and it was a bad cell in a battery that was only 6 months old.New battery and problem was solved.

[billydonn]

Originally Posted by salazar44

Hey guys. Im getting pretty frustrated! My battery keeps dying and I cant figure out why. I have taken my alternator in twice and they say its charging correctly.

its not like an overnight battery kill but more like a 30-40 start kill.

Any suggestions on how to diagnose this?

Have you rewired the truck in any significant way or added an accessory? Be sure you don't have something that should be wired hot with key on only wired "always hot". A good example would be an electric choke. Slow charge the battery overnight until it holds about 14 volts... then check bat voltage every few hours with a digital multimeter and write down your voltage... if it holds, you can prob. assume it is something shorting when it is ON. DON't disconnect the bat while engine is running!

http://madelectrical.com/electricalt...witworks.shtml
http://madelectrical.com/electricalt...charging.shtml
http://madelectrical.com/electricalt...-battery.shtml

[greg64]

Hey Vic, I've got to go with Billy on this; don't disconnect the battery while the engine is running. The battery acts like a big capacitor for the alternator and regulator. These aren't designed to properly control the voltage without the big source/sink of the battery.

If you don't have a digital multimeter (even a cheapie will do for automotive work), buy one. Then, with the engine running, check the alternator output voltage at the big terminal on the back of the alternator. It better be at LEAST 14V or the alt/regulator is bad. If it is 14V or higher (might be 15), then the alt and regulator are working properly.

Next, check the positive terminal on the battery to ground. If the engine has been running for a few minutes, this should be 13-14V. If it's 12 or lower, you have a bad connection between the alternator + and the battery + (not that uncommon on these old rigs).

If you've made it this far, then your charging system is okay. Now, it's time to look for drains while your truck is off. The bulb in series trick works, but if the drain is low enough (and yours might be since it takes weeks) the bulb probably won't light. In this case, you need an ampmeter that is good for about an amp. Most digital multimeters have some sort of a current range, but BE CAREFUL. Many are too puny for our needs (200mA). Ideally, you have a 0-10A range that you can use. Anyway, if you connect the multimeter on current between the positive terminal on the battery and the starter cable, you'll get the whole story. Now BE CAREFUL (there's that word again) while you have the meter connected in. If you deliberately turn anything on, it will, at the least blow the fuse in the meter.

Okay, so see what current is being drawn, and then start pulling fuses, etc. until the current goes to 0.

If you hate the current idea, there's another way that's safer.... Pull BOTH cables off the battery terminals (no juice) and patch the meter in using the resistance (ohms) scale. I would expect the resistance to read 20 ohms or higher. Now, keep pulling fuses until the resistance shoots way up. (at least 250 ohms, and the higher the better).

Also, as a last hint for all you guys chasing electrical gremlins, substitute your battery charger for the actual battery. This will limit the current in the event of a short, which will keep wires from burning up. Obviously you can't run the starter with only the charger, but everything else will work, and it's inherently safer.

[Ham-er]

Another possibility - If you have wired in a 3 wire alternator(new type with internal reg) but instead of feeding the "field" terminal thru the ignition switch you have have instead done a bypass. In that case the field winding will drain the battery overnight. Possibly not enough drain in one night to completely kill the battery.

the old external regulators would drain it in one night when they went bad sometimes or if the ignition switch idiot light combo was bypassed in this way.

The field terminal on the alternator is supposed to be connected thru the igniton switch and the "gen" light.

This kind of thing would cause the problem you are having! A constant slight battery drain at times when there shouldnt be any. (key off)

[64Magoo]

My first thought was exactly that of JChav. I had the same problem (3 batteries and 2 alternators in 3 months) and it turned out to only be my voltage regulator. I would check to see if the wires are all connected right, or even buy a cheap one at the store ($15) to see if that would solve the problem.. at least temporarily.

[protrash64]

I have this issue in both my trucks.........my pick-up I just disconnect the battery because it rarely gets driven......in my 'burb I popped for a solar battery maintainer which plugs into the cig lighter........works perfectly and worth the money.

My pick-up has 1/3 of a volt draining somewhere..........

[salazar44]

Well its not a short. Tested using the light method and it was good. Gotta check the alternator voltage now! Time for a meter!

[ValveTubeHead]

I went through similar symptoms with my external voltage regulator. One give-away, is that typically your electric gauges (temp, fuel and charge), dance around quite a bit more than they should, also headlights dim when you turn on an electrical accessory; heater fan, horn, a/c etc.

Many times oxidized connections can mask what appears to be a perfectly solid conductor. Take a hour or so with some rough sandpaper, and small nail file to go through all underhood contact points, connectors blades and terminals; clean them if oily and score the contact surfaces so fresh metal to metal connections are made.

A fair number of my connectors were dull and green. I replaced what appeared to be a new voltage regulator, and cleaned the connections as described, and haven't had a problem since. dos centavos

[greg64]

Hey Vic, have you found the drain yet?

Another thought for all you guys still running external voltage regulators; dump them.... It's so easy to change a Delco 10DN (external regulator) over to a 10SI (internal regulator). Cleans up your engine compartment a bit and the whole setup is more reliable, plus the SI puts out more juice at idle.