battery dead

[Twista89 10+ year member]

So I have a deka 9a31 battery in my trunk and have it hooked up to a battery isolator that went faulty and I didn't know. Recently got everything hooked back up but now my battery won't charge. With the car on its around 13 volts but when the car is off it drops down to 8 volts. I usually have the car on when I'm playing music so I figured my alt would charge it back up but it's been like this for the past few weeks. Is my battery shot or can I save it and how???

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[Kangaroux 5,000+ posts]

If it's sitting at 8v it sounds like it's long gone. You can try to put it on a 12v charger over night but it sounds like you got a dead cell or 2

 

[winkychevelle 10+ year member]

just about any time a batt drops 4volts below flating voltage its gonna be dead as far as blaming the isolator that for u to decide personally i dont se the need for an isolator

 

[Kangaroux 5,000+ posts]

OP take the battery out of your vehicle if it is dead. It will drain your front one real quick and then you'll have 2 dead batts

 

[Twista89 10+ year member]

gonna try and put it on a charger tomorrow. I took another reading earlier and it was at 9.5v so maybe it can be saved. The isolator is working now so those two batteries stay disconnected until the car turns on and the alternator is running.

 

[Kangaroux 5,000+ posts]

gonna try and put it on a charger tomorrow. I took another reading earlier and it was at 9.5v so maybe it can be saved. The isolator is working now so those two batteries stay disconnected until the car turns on and the alternator is running.

If it's resting anywhere under 12.0v it's usually on its last leg/dead...you definitely have a dead cell. Sorry man but that batt is gone

 

[audiobaun 5,000+ posts]

gonna try and put it on a charger tomorrow. I took another reading earlier and it was at 9.5v so maybe it can be saved. The isolator is working now so those two batteries stay disconnected until the car turns on and the alternator is running.

Not worth the effort in my opinion..batteries are DEAD for sure..I recently started out at 12.6v, and down to 11.6,and found batteries were no good..Replaced, and back up to 14.6v.No need for an Isolator,unless you camp alot??And need battery power for cooler/computer or?Ive never found a real use for one.Get yourself a good battery..most if not all vehicles these days need 13-14v to operate properly with all the electrical on board alone.//content.invisioncic.com/y282845/emoticons/santa.gif.e1ec9cf2e0a0dd232ad35aa594a126d0.gif

 

[Twista89 10+ year member]

Well i put it on a 16v charger for a hour and took it off and its sitting around 12.7 volts right now. Gonna let it sit for a while a see if it sticks around there.

 

[Twista89 10+ year member]

still sitting at 12.77 so I guess I might have saved it...Good thing AGM batteries are a little bit tougher than lead-acid...Reason I had the isolator was because I use to sit around and let the music blast for a while hanging out with friends...It was a couple of nights Id come out to a dead car battery so I added a Isolator to it...

 

[Kangaroux 5,000+ posts]

You put a 12v battery on a 16v charger? And even if it does seem to charge up fine doesn't mean it will hold its charge well...put a load on it and see how much it drops

 

[Twista89 10+ year member]

Yea Im pretty sure these batteries can handle 16v no problem...Ill go try ur suggestion though see what happens...

 

[Twista89 10+ year member]

Also is it damaging for my amps to see such low voltages???

 

[goingdef 10+ year member]

If you used a standard charger to try and bring that agm back up you most likely caused it to vent and even though it's holding a charge now it will die really soon due to the fact it's no longer sealed! Never charge a AGM with anything other then an approved charger unless you like buying new battery's, I learned this the hard way but thankfully was still under warranty!

 

[Twista89 10+ year member]

Well it didnt vent to my knowledge as I was in the garage the whole time while it was charging. I went back outside as its been 4 hours since I took it off the charger and it was still at 12.77. I played some music for about 15 minutes at half my normal playing volume and it dropped down to 12.56. If its still at 12 volts by the time I wake up tomorrow ill keep it around. I dont listen to much music with the car off anymore so I really dont need it other than to help supply to my sundown. I need to upgrade my subwoofers as well so my amp isnt even tuned all the way yet....

 

[mlstrass 5,000+ posts]

why not just get it load tested to see if it has bad cells? autozone or any place like that will do it for free...