i recently left the key in my switch with the switch on. the next morning my batteries were dead. i mean stone cold dead the key in the switch bell would not ding. got it jumped of and as long as the air temp stayed above 45 she would start no problem. they definately do not have much reserve power in them. will draining them that low kill them? they are 4 years old from advance auto, silver

Draining a batery to 0 Volts does serious damage to them most times. Normal car/truck batteries are consider dead at about 11.8-12.0 Volts below this point damage to the plates start occuring. Remember car/truck batteries are NOT deep cycle batteries so they do not tolerate being discharged deeply and then recharged. Maybe that way my factory orignal batteries at still going yet...

4 years old is a long time on a battery. A run-dead can push it over the edge. So yes, your batteries have one foot on a banna peel. The good part is you have the time to plan the replacement... if there's a warentee, collect it now. (I kept a set of batteries going an extra winter by plugging the truck in at night.)

Draining a batery to 0 Volts does serious damage to them most times. Normal car/truck batteries are consider dead at about 11.8-12.0 Volts below this point damage to the plates start occuring. Remember car/truck batteries are NOT deep cycle batteries so they do not tolerate being discharged deeply and then recharged.

Maybe that way my factory orignal batteries at still going yet...

kinda figured that. when i was in OK at 45* with 12.3 volts they wouldnot start it. might have turne 3 reveloutions before crapping out. but this morning here in NC with 12.15 volts at 50* it fired right off no problem. guess i will be getting some new ones soon.

--- Update to the previous post...

4 years old is a long time on a battery. A run-dead can push it over the edge. So yes, your batteries have one foot on a banna peel. The good part is you have the time to plan the replacement... if there's a warentee, collect it now. (I kept a set of batteries going an extra winter by plugging the truck in at night.)

i got 6 years out my oe batteries and changed them out because they seemed to be getting a little weak, they never failed me though. there might be little warranty left have to check. they seem to work better after cleaning them up and charging them. but i agree with the bannana peel.

When you replace them, do them at the same time! You will have troubles if you only replace one.

ALWAYS!!!

When you replace them, do them at the same time! You will have troubles if you only replace one.

would never do it differanly than bothat once.

The problem is not just volts, though a weak / shorted cell will show up as low volts. The problem is that while the batteries appear to charge, it is just a surface charge & under load the voltage will collapse as the batteries can no longer deliver the amperage. A battery load tester will show this.

i dont have a load tester. i did bleed off the surface charge by turning on the high beems for a periond of time before checking the voltage. dont remeber how long think i read that in the haynes manual. Autozone tested the batteries and said they were good, but i am not convinced. we will ride it out a little whil and see what happens.

It could be AZ doesn't want to cough up... but have you cleaned the battery cables, lugs & the cross link... give a good look at the cable to lug end connection for damage (stranger things have happened)? You could also use a multi-meter to check for voltage drop first on the hot side & then on the ground at each connection (lead battery terminal, lead connector lug, copper conductor). Am I making sense?

I cleaned up all of my connections the other day when i charged the batteries. did not have time to test any thing though. seems to be working alright but have not had to crank on hard since i got her up and running after the ad install. not sure i trust the battery check at AZ. the batteries came from advance auto. i will let them check it out and see what they find. they are probably border line good and since its their warranty i bet they check out good. we shall see.

I had some slow crank at the end of the winter from my truck, but the batteries tested good as well. All terminals clean, etc. I think the extra load from more advanced timing that did mine in.I checked for parasitic loads and I was seeing almost 3a of key-off draw. I've had my radar detector hard wired ever since I've had the truck and it never caused any issues even sitting on, for as long as a week, but about 2.5a of that draw was the Valentine One. I've started keeping that off, and it seems to have been enough.If your issue isn't one of instant restart, do check for parasitic loads.That said, Mike is absolutely right with damage being possible with deep discharge. Desulfication can sometimes bring a dead one back to life but yours are at the age that it's debatable... If you have other vehicles with lighter demands it might be worth a shot, to have spares for them!

My Escort SR7 radar system comes on with the key in my truck (I like the system but it was a lot of money). I had my GPS run down my car... someone plugged the cord back in which turned the unit on... over night... I know the battery was weak but that was a surprise.

I was lazy and borrowed power from the dome light circuit instead of running down the pillar to a switched source