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My battery keeps dieing although it's only a few months old. I charge it every night. I ran some tests today (to the extent of my knowledge) I measured 11.8v coming from the alternator, and 20amps. Something doesn't add up to me there. I then measured total current draw and everything works fine, battery keeps charging, but any sort of big load like the AC or lights seems to kill it and it starts drawing 15-20 amps from the battery. Any ideas?
If you hook your tester to the battery, you need at least 13.5 volts to charge the battery. This should be with engine running and as many accesories on as possible on as possible.
My battery keeps dieing although it's only a few months old. I charge it every night. I ran some tests today (to the extent of my knowledge) I measured 11.8v coming from the alternator, and 20amps. Something doesn't add up to me there. I then measured total current draw and everything works fine, battery keeps charging, but any sort of big load like the AC or lights seems to kill it and it starts drawing 15-20 amps from the battery. Any ideas?
Hi
Looks like you have an alternator issue. Make sure there's correct voltage (and ground) getting to the 2-pin connector at the back of the alternator. If this is good, you should have from 13.5 to 14.2 volts coming out of the alternator with the engine running. Anything lower than that means the alternator has failed and needs to be replaced. cheers
Sounds to me like the alternator has died. Number one, does the battery light on the instrument panel light up with the ignition on and engine not running? If not, check that the globe is OK and that the connector is firmly attached to the rear of the alternator. You can earth out that lead and if the globe is OK it should light up. Also check the fuse feeding the ignition circuit. If that part is crook you won't excite the alternator and you won't get any output.
Start the engine, and with a voltmeter connected to the battery check the voltage. It should rise up to about 13.3 volts, and then as the battery charges (assuming it is on the flat side) it should rise to about 13.9 to 14.3 volts. Under normal circumstances (ie a well charged battery) the voltage will peak up to about 14.3 pretty quickly and then over some time drop back a bit as the inherent thermal compensation kicks in. That's what a working alternator should do.
As for the current, the battery should charge with anything between 3 and 10 amps. The alternator though will push out more than that as it runs all the car electrics such as radio, lights, fan etc. You're typically looking at 15 amps upwards. This will change as the load comes on and off, and also as the battery reaches its fully charged state. Reading volts is relatively easy with a DVM. How are you measuring the current (what with) and whereabouts in the circuit are you measuring it?
Check out all that. I suspect the alternator is crook. BTW, you haven't got a loose drive belt have you? That will kill an alternator too.
I had a belt break off and I replaced with a newie but was loose and making squealing noises, but I had to drive to work and didn't get to tightening it for a few days then it magically stopped squeaking. I was thinking maybe I did kill the alternator doing this, would the loose belt cause too much heat in the windings?
I tested the alternator with a shunt type ammeter. To be honest I dont think I measured anything much over 12v.
I've found that driving with no accessories on will keep the battery charged fine. Since summer's coming I suppose I'll be looking at a new or reconditioned alternator then?
What is involved in reconditioning an alternator, and how much would a good one be worth?
I have a few extra accessories such as 3 fans on the radiator and condensor so should I be going for a higher power alternator?
I had a belt break off and I replaced with a newie but was loose and making squealing noises, but I had to drive to work and didn't get to tightening it for a few days then it magically stopped squeaking. I was thinking maybe I did kill the alternator doing this, would the loose belt cause too much heat in the windings?
I tested the alternator with a shunt type ammeter. To be honest I dont think I measured anything much over 12v.
I've found that driving with no accessories on will keep the battery charged fine. Since summer's coming I suppose I'll be looking at a new or reconditioned alternator then?
What is involved in reconditioning an alternator, and how much would a good one be worth?
I have a few extra accessories such as 3 fans on the radiator and condensor so should I be going for a higher power alternator?
Cheers
It's hard for us to give much of a price on an alt. since you've never told us what kind of vehicle or what year. We could guess an E series Falcon assuming this is posted in the correct forum. A loose belt tells us either your tensioner is weak, or you have an older vehicle with more than one drive belt, and that you just didn't get it tight enough. As far as the squealing, you may have a pulley bearing on something going out. Based on your voltage output, it sounds like your alternator is not charging as it should.
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