HELP! My 2007 Prius is dead....(12 v battery....?)

wow, that's the first time i've seen oem cheaper. they have a very good warranty now.
but after 5 or 6 years, they're all a crapshoot.

 

Unless I misread your earlier post, you said your dash lights were lighting up when your charger WASN'T hooked up but then going out again when you turn the charger on. That doesn't sound right -- I'm thinking maybe a short somewhere in your 12v system killed your battery and would quickly kill any replacement. Doubly so if you're already on an Optima, those things don't really die under normal operating conditions.

Any chance you're able to read the check engine code while the dash lights are on?

 

My Optima came from the Amazon link in my earlier post, for the $160 price, and is working fine for me.

You said you have a charger. Why not take the Optima you have now out, leave it on the charger while disconnected from the car for a few hours then test it with a voltmeter to see if it's recovered? Those Optimas are built to recover well from being discharged, and isolating it from the car would mean if there *is* a short somewhere it won't immediately drain the power your charger is putting in.

 

7 years? everyone who doesn't know anything about a prius battery?

 

4 volts? Unless you've left the car undriven for at least a couple of weeks without turning off Smartkey, something's up there. That's some serious discharge.

 

You can remove the battery in the back and just hook up the charger leads in its place and tape them up and put a blanket under them so they don't catch a frame ground and before u start the car see if the headlights come on. If not then you have blown a a fuse either the one thats in the red post assy that attaches to the battery or the dome fuse or the big one in the fuse box up front under the hood.

No headlights do not try to start the car and get professional help. Or at least someone who knows how to use a voltmeter.

We have seen this countless times. Sometimes this ends very badly so move cautiously.

 

Sounds like you're on the right track now, Frank. I just found your thread. Only having 4 volts on the battery with no load on it after having been on the charger as long as you've had it on is a dead give away that the battery is done for. You MIGHT be able to desulfate it with a really good charger, but it's unlikely. As soon as I read how old it was, I was pretty sure it was a failed battery. Some people tell me that most batteries down here in FL only last about two years. I think that's a little pessimistic. Most of mine go about four years. And my cars sit in the sun almost 24/7. In a garage, they might last longer if it's not so hot. So I think you got your money's worth out of it.

That doesn't rule out the possibility of a drain on the old battery that killed it, so I'd keep a close eye on the new one for a while when you get it. The thing about batteries here in regular cars is that the engine is usually not cold, so it's easy to crank. Prius auxiliary batteries are even more sneaky. Hope the new battery is all it needs.

 

No way it was drained from anywhere around the normal 12v to 4v in less than 48 hours without some kind of short being up. 10v is a dead battery, down to 4v in under 48 hours is a 12v system problem.

As far as the headlights go, I do not know about your Prius, but in my 2007 the headlights turn off automatically when I turn the car off. The Smartkey radios are normally the only thing that puts a serious drain on the 12v when the car isn't on, and it's nowhere near a serious enough drain to bring you down from anything that would actually successfully start the car to 4v in under 48 hours.

Looking at the first page of this thread, by the way, there seems to be a lot of discussion of sulfating... Sulfating is something that happens when a battery sits around without being charged or discharged for a long time. In other words, when a battery sits around on the shelf at the store, or if it sits around in a car that isn't getting driven. The point of trickle chargers is to prevent battery sulfation. If you've been driving somewhere around 35 miles a day in this car, your battery in all likelihood has little or no sulfation.

There was an actual drain on it. I'm almost certain you've got a short somewhere.

 

The 11.84V is below the normal values. A fully charged battery should read about 12.80V. I believe you won't be able to get the Prius in ready mode with 11.84V.

 

cold vs under load is different.