I have a 96 B2500 van, 315 v8. The battery is about 7 months old, and I did a test today with a voltage reader, and the battery read the normal voltage when running and when off. Also, the car continued to run with the battery disconnected, indicating that the alternator was working properly.

So, why is my battery draining? I'll jump it, let it run for a while, shut it off, and a few hours later its dead as can be.

A little background that may or may not be relevant: About a week or so ago, some of the interior lights stopped working. I have a converted high top van, so it has indirect limo style lighting in the rear. Those lights stopped working, and 2 of the overhead lights in the rear stopped working also. Van drove and started like normal up until 2 days ago. 2 days in a row I jump started it, let it ran, and then it wouldn't start a couple hours later.

From the tests I did today, it seems like the battery is good and the alternator is good. Where do I start looking for the problem now?

 

Never-ever-ever disconnect the battery to determine if the alternator is operating. It can destroy the alternator, it can also destroy the vehicles electronics as the voltage can quickly spike up into the 40's and 50's and beyond.

Whoever told you to do that, go upto them and smack them upside the head.

Read this:
http://www.aa1car.com/library/charging_checks.htm

It might have been a viable test when vehicles used generators but is an old wives tale which should just die. It has no relevance to any vehicle designed after say '65.

When A battery needs to be jumpstarted, it needs at least 5 hours of highway driving before it approaches 80% charged. And another 5 hours to go from 80% to 100% charged. 15 minutes might recharge it just enough to restart it 6 hours later, but no more.

You need to put the battery on a real battery charger overnight and longer if it is less than a 10 amp charger. Whenever a battery sits less than 80% charged, it is sulfating. Each day as more sulfates form, the harder the older ones get, and the more battery capacity is lost, and the less likely that it can ever be revived.

To test for a battery drain, You need a digital multi meter. You set it to DC amp function. Hook up the leads in between the disconnected negative battery cable and negative battery post. It will read a number. You disconnect the fuses 1 by 1 till this number goes down to about 40 milliamps. When this happens you have isolated the circuit with the drain. Then you need to investigate that circuit.

I don't think you have a large electrical drain, I think you are just overestimating the alternator's ability to recharge the battery by a factor of ten or twenty, and right now as your battery sits down in the 30% charged area, it is dying.

And there is a good chance you blew some diodes on the alternator . If it was once rated at 90 amps, it might now now only be able to produce 60 or 30 amps, and is also introducing AC electricity into your DC electrical system wreaking havoc on the computer and sensors. So instead of taking ten hours of highway driving to fully charge the battery you might be looking at 16 or 22 hours.

At Idle speeds a healthy alternator on our vans will need about 24 hours to fully recharge a formerly healthy battery that had to be jumpstarted. This is true of most vehicles too, give or take 10 hours.

 

Wasn't it you that suggested to do that, in another post?

 

Try to find the post where I recommend doing that, you wont.

 

SO are you guys saying, that from the wive's tales method of testing the alternator (disconnecting the battery)... I might have fried the alternator just doing that?

Also, from reading these articles and learning some helpful info, it seems that any diagnosis of anything electrical will be off until I have the battery at full charge? So, I should put the battery on a charger until 100%, then break out the voltmeter again?

 

Fully charge the battery. Have it load tested. A bad battery can still show 12.8 volts but have no capacity. A load test can show this.


You can do your own version of a load test. Full charge it, hook it back up to the van, turn on the headlights on high beams, turn the blower motor on high. This draws about 34 amps on the battery. If the battery voltage drops below ~12.4 after a minute of providing this amperage it is weak. If it instantly falls into the 11's, go get a new battery.

There is a chance you damaged the alternator, I'm not saying it happened. Worst thing you can do to it (after disconnecting the battery while running), is ask it to recharge a dead battery. They are not designed for that. Charging systems in vehicles are designed to return the charge used to start the vehicle, and power the vehicles accessories. And they are woefully inadequate at that at idle speeds.

If your battery is over 5 years old, just replace it.

If you've had to jumpstart the vehicle more than a dozen times and have not put it on a charger immediately after returning home, just replace it no matter it's age. It might go another month or 2 but it will leave you stranded soon, at the worst possible moment.

When you remove and reconnect the negative battery terminal, and if you see a good sized spark, that is a sign that there is an electrical demand. Doing this to a battery which is low on water and has been charging can be dangerous, which is why when jump starting they say to hook the ground to the engine, so the spark happens there instead of on the battery where hydrogen might be present and go boom.

 

The battery is only about 8 months old. Could I just take the dead battery to the auto parts store and have them load test it? Or does it need to be charged 100% to perform a load test?

 

It should be at 100% for an accurate load test.

However if you want to replace it under warranty you might just want to charge it enough to read 12.8 volts. After a battery is charged, it holds a surface charge, a higher voltage for an hour or 2. This is why you can jump start an engine, run it for 15 minutes, and start it again an hour later, but not 6 hours later.

Depends on the guy doing the load test, and their equipment, and the batteries ability to hold a surface charge whether they recognize this or not. Generally if the Van's charging system is healthy and you drive it to the store, quickly remove it and have them load test it, you have a better chance of getting a new one under warranty.

Before charging it, look for the spark when removing and replacing the negative terminal. If a large spark is present, then something is causing a battery drain, if not either your 8 month old battery is just a piece of junk, or you just depleted it and never adequately recharged it, causing it's premature death.

Good luck

 

I know, I was just messin' with ya!

 

You had me doubting myself, for about 1/4 second, so well done!