Uh oh...is it the batties or alt...?

[CRXBMPN 5,000+ posts]

It is going to take longer than 15 minutes to charge 2 almost totally dead batteries. I would get a Ctek MUS 7002 charger and charge up the cells independantly to see if you can bring them back. Even if it doesn't you have a good charger to help avoid this type of situation as a low battery is hard on an alternator anyway. Chargers like this charge more complete than an alternator as well that will mean longer battery life and better performance over the lifespan.

correct, you need to charge your batteries from dead for more than 15 minutes... more like an hour of your car being on with the (working) alt charging them and filling them back up instead of just a quickie surface charge. in my situation I was lucky that my batts were not dead at all and a 15 minute jump just gave them some more oomf in case.

 

[audiolife 5,000+ posts]

One of these can save a lot of money catching something not wired right, not working right to just leaving the car sit for too long Amazon.com: CTEK 56-382 Comfort Indicator Eyelet: Automotive

 

[05trailblazer 10+ year member]

i hate this kinds of cenarios

 

[Davecubs14 10+ year member]

Ok. Well I let it charge for a while this morning. It's been sitting for 4 hours now and it's already gone from 12.4 to 12.0. I'm heading off to autozone to check everything.

 

[audiolife 5,000+ posts]

If it is resting at 12 volts thats far from being charged, you need a good intelligent agm battery charger.

 

[Davecubs14 10+ year member]

They're resting at 11.6. And yeah....that's what o'reily's said. So....Idk! Might as well switch up both batteries and alt! Shoot..

 

[dbjunior 10+ year member]

id take out your second battery and put that on a charger let your car charge your main battery, one dead battery will drain the other down. separating them will help you identify the bad battery.

 

[Davecubs14 10+ year member]

Already did that. Just haven't charged the back battery. The front one won't charge either. I totally forgot but I still have my old alt in the attic. I'll dig it out tomorrow and switch them out....

 

[audiolife 5,000+ posts]

What are you using as a charger?

 

[tenbux1970 10+ year member]

Just guessing here... I would have to guess that the bearings are bad in the alt.

If the voltage is dropping slowly the diode plate in the alternator is dead.The purpose of the plate is to stop the reverse flow of electricity.With a reverse flow of voltage that turns your alternator into a heater,and that drains your batteries.

Have you checked the alt shaft for movement? If you still have the stock alt (or any other alt) put it back on for a "test" period.

 

[RAM_Designs 5,000+ posts]

With those batts you'll probably need to do a 2amp charge for a few hours to get it to hold a charge better. Doing a quick charge with a higher amperage isn't going to help.

 

[audiolife 5,000+ posts]

With those batts you'll probably need to do a 2amp charge for a few hours to get it to hold a charge better. Doing a quick charge with a higher amperage isn't going to help.

Using an intelligent charger that senses sulfation helps a lot too. Another way is with an adjustable voltage power supply and patience

 

[Davecubs14 10+ year member]

Sorry guys. I'm just lost when it comes to this. I don't have a battery charger. And i've ran the same electrical for 2 years now and all of a sudden, the batteries won't hold a charge. Since I don't have a charger, would it be a good test to put my old alt back in there and see if it could charge the batteries?

 

[-01limited- 10+ year member]

Disconnect positive of battery while the car is running and if your car doesnt die your alt is fine.

 

[Davecubs14 10+ year member]

Ok. I'll try that.