help diagnose battery killing issue (1 Viewer)

[sven]

Battery tested good and only year old. Truck runs once cranked but if battery left connected overnight, battery will be nearly dead (now dead) in morning. After running truck for a while, will re-crank on its on. Advance Auto says alternator but can't explain it, just says the machine says alternator. Charge system test showed:
no load 13.16V 6.9A / loaded 13.18V 6.1A. Drain test showed .031A. Once running, if I take off the positive off battery, keeps running the same. I may need to just go through the drain test procedure with a meter but was trying to take the easy way out. Thanks in advance. BTW no aftermarket stuff connected to battery.

 

[John McVicker]

Battery tested good and only year old. Truck runs once cranked but if battery left connected overnight, battery will be nearly dead (now dead) in morning. After running truck for a while, will re-crank on its on. Advance Auto says alternator but can't explain it, just says the machine says alternator. Charge system test showed:
no load 13.16V 6.9A / loaded 13.18V 6.1A. Drain test showed .031A. Once running, if I take off the positive off battery, keeps running the same. I may need to just go through the drain test procedure with a meter but was trying to take the easy way out. Thanks in advance. BTW no aftermarket stuff connected to battery.

Are the 13.1's at the batt. or at the alt. ??

John

 

[cruiser88]

you lost your reserve minutes.........go by autozone and get a free test. This will become evadent in the cold hense it requires more cold cranking amps to start in the colder weather.

Battery tested good and only year old. Truck runs once cranked but if battery left connected overnight, battery will be nearly dead (now dead) in morning. After running truck for a while, will re-crank on its on. Advance Auto says alternator but can't explain it, just says the machine says alternator. Charge system test showed:
no load 13.16V 6.9A / loaded 13.18V 6.1A. Drain test showed .031A. Once running, if I take off the positive off battery, keeps running the same. I may need to just go through the drain test procedure with a meter but was trying to take the easy way out. Thanks in advance. BTW no aftermarket stuff connected to battery.

 

[augirthedude]

A DC amp probe would be a handy tool for this diagnosis, Most good ones are pricey

 

[ntsqd]

Taking the positive battery cable off while running can pop the alternator's rectifier diodes. Strongly suggest discontinuing that practice.

 

[cruiser88]

yep...........

Taking the positive battery cable off while running can pop the alternator's rectifier diodes. Strongly suggest discontinuing that practice.

 

[djawahir]

Check the grounds in the truck along with the starter wire from the battery too. Clean connections really well. You can start popping some fuses to see what is going on. You may have a bad relay somewhere too although it's a long shot...

 

[Cruzerman]

Seems to me that either something is draining the battery, the battery isn't getting a charge, or the battery won't hold a charge. 13.1 volts from the alternator is a kinda low. I would expect at least 13.5 volts or more. So the alternator is still suspect.

I'd start by taking off the positive terminal and inserting your VOM inline between the battery cable end and the positive post on the battery. Turn the VOM on to DC amps and see if there is any draw with the key off. If there is, then something is draining the battery. You can then take out fuses one by one until the drain stops. This will help narrow down what circuit is draining the battery.

If there isn't any (or very little) amps showing on the meter, then it sounds like either the battery isn't getting a good charge or it isn't holding the charge. I'd charge the battery to full. Let it sit overnight or even a couple days and then in hook it back up. If it won't turn over or doesn't turn over well, then you know it must be the battery not holding a charge since you've already ruled out the possibility of it being drained and the battery wasn't even hooked up. If it does work just fine, then it just must not be getting charged when the engine is running and so must be the alternator.

 

[rusty_tlc]

Battery tested good and only year old. Truck runs once cranked but if battery left connected overnight, battery will be nearly dead (now dead) in morning. After running truck for a while, will re-crank on its on. Advance Auto says alternator but can't explain it, just says the machine says alternator. Charge system test showed:
no load 13.16V 6.9A / loaded 13.18V 6.1A. Drain test showed .031A. Once running, if I take off the positive off battery, keeps running the same. I may need to just go through the drain test procedure with a meter but was trying to take the easy way out. Thanks in advance. BTW no aftermarket stuff connected to battery.

1) The battery loses charge overnight, this indicates a short to me.
2) The car will re-start after running for a while, this tells me the charging circuit is probably working.

What exactly is "Drain test"?

 

[inkpot]

Howdy! I went thru this on my FJ 55. I disconnected everything I could trying to find a drain/short. No luck. Replaced the alternaotr, TaDa!! No more problem. It had a small internal short that was draining the system overnight. Ya know what I'd do?? John

 

[cruiser88]

the drain test is pretty standard. You moniter the battery voltage ,amps...bla bla bla to see if the battery can keep up with usage.

Usually when a rig will not start in the cold or even hot...more so in the cold the reserve minutes is zapped. Reason behind it is because of the cold the vehilce requires more starting amps than the battery has availble. Just because the voltage is there doesnt mean all is good. 13.1 volts is more tham enough to turn it over if the amperage is presant

13.5 is excellent if its running.

1) The battery loses charge overnight, this indicates a short to me.
2) The car will re-start after running for a while, this tells me the charging circuit is probably working.

What exactly is "Drain test"?

 

[cruiser88]

wire the fusable link up to a 50 amp plus switch

Howdy! I went thru this on my FJ 55. I disconnected everything I could trying to find a drain/short. No luck. Replaced the alternaotr, TaDa!! No more problem. It had a small internal short that was draining the system overnight. Ya know what I'd do?? John

 

[augirthedude]

even high quality multi meters can be as much as +- .5 volts off. Check all leads from the battery individually wjith the eng . off for any amperage draw. follow the amps and this will lead you to the drain. also you should load test your battery with a load tester. check the specific gravity of the battery electro lyte .

 

[LAMBCRUSHER]

bad diodes. r+r alternator.

 

[sven]

man, thanks folks! got some homework to do...

couple things
1) taking the pos battery cable off while running was done once as a quick (and apparently stupid) test;
2) battery terminals are all clean and tight;
3) volt numbers were from battery by autozone zombie; really went there to use their DC amp probe which he says they don't have;
4) had the alternator "rewound" by a local shop about 6 years ago so I may start back there;
I guess the thing I wasn't understanding is that when I can barely squeeze off a crank, then run drive the truck for some time (hour), the battery is then strong enough to crank right off, which makes me think the alternator is good. Thanks again, got some lookin to do.

 

[rusty_tlc]

It's pretty easy to pull the alternator and take it in for a bench test. I'm a bit confused as to how the system would charge with a bad diode but it wouldn't hurt to eliminate that as a problem. When trouble shooting I always go for the low fruit first.

I think you will wind up putting an ammeter in series with the battery + terminal and pulling fuses until you find the faulty circuit.

 

[ntsqd]

couple things
1) taking the pos battery cable off while running was done once as a quick (and apparently stupid) test;

Not stupid, just uninformed. It seems like a logical test to do.

It's pretty easy to pull the alternator and take it in for a bench test. I'm a bit confused as to how the system would charge with a bad diode but it wouldn't hurt to eliminate that as a problem. When trouble shooting I always go for the low fruit first.

I think you will wind up putting an ammeter in series with the battery + terminal and pulling fuses until you find the faulty circuit.

This can happen with a "leaking" diode. If you hear static in the radio that changes it's pitch with engine RPM then I'd suspect that possibility and investigate it further. The mere presence of the static isn't conclusive proof, but it can be an indicator.

BTW, you don't need an ammeter to do the fuse test. Just a test light between the battery terminal and the battery cable will tell you which circuit is the one with the problem.

What would be good to know is what the battery voltage is when cold cranking after having topped it off and let sit disconnected overnight. Measure the voltage right after topping off, just before reconnecting, and again while cranking the cold engine.

 

[rusty_tlc]

@ntsqd
a leaky diode makes sense thanks.

 

[brett76]

1) The battery loses charge overnight, this indicates a short to me.
2) The car will re-start after running for a while, this tells me the charging circuit is probably working.

What exactly is "Drain test"?

lol i just went through this. turns out the nut was lose holding the wire to the solenoid on the starter.

i agree with rusty
suggest you just check all connections and grounds. something loose and shorting out

 

[cruiser88]

you dont even need to do that.........autozone has a awesome snap on tool that does batteries, alts and starters.

It's pretty easy to pull the alternator and take it in for a bench test. I'm a bit confused as to how the system would charge with a bad diode but it wouldn't hurt to eliminate that as a problem. When trouble shooting I always go for the low fruit first.

I think you will wind up putting an ammeter in series with the battery + terminal and pulling fuses until you find the faulty circuit.