Apparent Dead Battery - To Jump or Not to Jump

I've had mine sit for two weeks idle and start up fine. This may be a case of a defective battery from the factory.

Lead-acid batteries normally are permanently damaged from a deep discharge, frequently fatal damage. There are aftermarket batteries like the Optima that are designed to survive a deep discharge. I'll get one of those when my battery shows signs of dying.

 

Mine died 5 days after I left it on parking lot, but I wasn't driving it too much prior to this - just once a week, so I guess it was constantly undercharged.

The battery can discharge faster also if you have aftermarket alarm installed. Or a car stereo improperly installed.

 

I've heard of enough battery failures from improperly designed or installed car alarms, both online and from real acquaintances, to demand that the alarm be completely disconnected from power. If it has an immobilizer that disables the car if the alarm controller loses power -- which you may have, if they didn't simply shut it down by pulling a fuse or disconnecting power -- then I'd demand that the unit be removed. Or at least remove enough that the remainder can be disconnected from power.

Unfortunately, having two separate dealers involved could complicate matters if they start pointing fingers at each other. If your selling dealership is good, they should take care of it.

Because of numerous poster's battery issues, I'm getting increasingly tempted to get the 'smart' jumper cables, the sort where the user doesn't need any clue about polarity, because the controller in between the terminal clips figures it out on its own and electronically connects the clips correctly. I think Jimbo has posted links to an example. Yes, here it is. Your short-term problem would very easily be solved by a jump start, and fear of a known hideously expensive user error appears to be the primary roadblock.

My early concern about AGM vs. normal batteries with regular chargers had been the end of the charging cycle, where the preferred profile differs. This is why I would take it off the charger early and let the car itself finish the job. The initial part of the cycle is not a problem with my dumb charger, which shows me what the charge current is doing, and my bench power supplies, which let me force anything I want. But that initial part is where your smart charger is hanging up, and the lack of a current indication kept you from seeing the problem.

They are a necessary evil. Can't live with them (though individual establishments vary widely), can't live without them.

 

Haven't had to do with with a Toyota dealership yet but I've had good luck in the past contacting my salesman and involving them when I have trouble with service.

The sales guy has a vested interest in maintaining a good relationship with you, if he has the slightest inclination to get your repeat business for himself. As such, he's more likely to go to bat for you than the service guy who you're struggling with.

My Mazda had a problem with a headlight that intermittently quit. After a couple trips to service and getting different stories, I walked over to the sales floor and talked to my sales guy. He got me squared away. (and if he hadn't retired, I would have gone to him when it came time to replace the mazda).

 

CCA is cold cranking amps. If they didn't chill it to 0F and cold soak it first, they couldn't have measured CCA. That is more likely a warmer temperature result, and I'm betting it isn't translated to cold conditions.

Are you equipped to measure the parasitic load? I'm not sure what the correct number is, but anything over a very few tens of milliamps should be raising red flags.

 

Hello,

I just got back from the a 12 days trip and attempted to start my Prius which has been sitting in an unheated garage. When I tried to start it, there was no response, so I used jumper cables to start it which worked right away. I ran in the house to get something, and when I came back out, the tail lights were dim and the car would not start again. Once again, I used another car to jump start it, and the same thing happened - about 4 minutes later, even after taking it up and down the street, it died after sitting idle again.

The Prius is a 2010, but already has 42,000 miles on it. I leave it on a lot, and sit idle because of my work. Before I left for my trip, I noticed the power was lacking slightly - but enough to notice.

Is it possible the 12V battery is dying? Thanks, Aaron

 

So you turned it off between jumps? If so, that's your problem. It takes hours to recharge the 12V battery; you can't do it in a few seconds.

It isn't necessary to drive your Prius to recharge the battery like you do with a normal car. Since the 12V system in the Prius is powered by a DC to DC converter and not an alternator, high engine revs do not help. Power up the Prius and let it sit in Park for a few hours.

If your battery doesn't hold a charge after that, then it's time for a new battery.

Tom

 

Thanks Tom. I tried jumping it again this morning, and this time all electronics came on, but the engine would not start. Is that a definite sign of a battery or should I let it sit like you said for a while?

Got your message about the double post. Sorry, I am a newbie.

Aaron

 

Amazon.com is currently out of stock, Buy.com has them
Buy.com - Michelin 5100 Smart Jumper Cables w/ Surge Protection

 

if you kill these batteries... they tend to stay "Killed" till you rebuild them or give them a nice long charge. if your battery is dead then you need to let it sit attached to jumper cables for a good 30 seconds to a min... maybe a few mins. if the 12v doesn't want to up it's voltage it will basically work as a short.

when my first 12v started to die on me, there was a point where i had to disconnect the 12v in order to jump the car. the dead 12v was sucking all the available juice before the car had a chance to power up. then the car would spend all day trying to pump power into a battery that wasn't holding it. there were a few times i kept the 12v disconnected and ran directly off the jump box (actually, about a week or two... i was short on funds for a new battery)

(random) in my opinion, you can hook up your 12v to a running car... just don't let them rev it. (this way you don't suck a heathy charge out of the jumped battery). a prius doesn't take a whole lot of power to start up... a fraction of what a starter motor requires. most the draw would be from the extremely low voltage battery in your prius since at first it wants to be matched to the jumper battery.. but there is no power control... it's dumping into the prius battery as fast as it can which isn't healthy. that's why i recommend to disconnect the 12v when starting... when the car is on, it doesn't need a 12v battery. just be sure to re attach it before going anywhere.. if you power off without a 12v connected you have to crawl into the hatch and manually open the hatch.... or jump in the hood area to get your power back...

 

The engine should always start with a jump unless the 12V battery is shorted. The engine starts from the HV battery, not the 12V like on a normal car. Jumping usually allows all of the 12V electronics to boot up, at which point the HV battery connects through a relay and all is good. If your 12V battery is really, really bad it can load down the 12V bus and keep the electronics from booting properly. In this case you need to replace the 12V battery, allow it to charge for a bit during the jump, or put it on a charger. Regardless which method you use to get it started, you will likely need a new 12V battery.

Tom