Problem starting Prius

Hi Jim,

How many miles do you drive your car each week?

The most recent time that you jumped the car and got it to start, how long did you leave it READY?

If you are driving the car sufficiently to keep the battery charged but it intermittently causes you a problem, then I suggest the 12V battery needs to be replaced (which probably is covered under warranty given your model year.)

 

I'd check the bettery terminal connections. If only a spark did the trick sounds like you might have a little corrosion starting at the terminals.

 

Hi Jim,

After you had jumpstarted the Prius, how long did you allow the car to run before you turned it off? (Did you allow enough time for the battery to recharge?)

Assuming that your voltmeter is working properly, if the voltage that you measure across the 12V battery is so low (i.e., 6V), then clearly the battery is bad.

 

+1

You may have multiple bad cells in your 12v battery.

I would suggest putting the battery on a charger until you get > 12.5V with no load, then letting the battery sit for ~12 hrs and see if the voltage stays above 12V or not.

I once had a battery that would charge up to 13V but then would lose the charge and drop back to ~10V overnight.

 

As for the voltage jumping up immediately after the jump, remember that the 12V bus on the Prius is powered from a DC to DC converter, which draws power from the big traction battery. All your jump has to do is briefly bring up the 12V bus so that the computers boot and the relays close. After that you can remove the 12V battery from the system and it will still function. There is no heavy starter draw as there is with a normal car.

Tom

 

Yes but unlike your Passat please be aware if while the headlights are on if you open the door in a hurry before you shut the car off the headlights will not automatically go out.That will bone you good if you run your lights on in the daytime.
I suspect the initial battery going dead issue was something you left on
and once you kill a car battery its usually flakey from there on out. Some on this forum disagree with this opinion. A car battery sulfides up real quick when you kill it. Your post saying it takes very little to get it back to 12 volts supports this. It will not take and hold a charge. Pull the battery out and take it to an auto parts store and they can load test if for free. In the meantime be aware this little battery will leave you when you need it the most and bottomline stop jumping it!!

 

The correct (and probably safer?) procedure for jumping a negatively earthed car, is to connect the red cable first, and then the black jumper cable. To disconnect reverse the above procedure. I can't remember the reason for sure but I think it has to do with reducing the spark, which isn't a good idea with the potential for the ignition of flamable gases/vapor, and the possibly the increased risk to damaging one of those ECUs.

 

Yes, in general you are supposed to connect the red positive side first, followed by connecting the black negative side. The black cable first connects to the donor battery and then to a bare metal spot on the chassis of the recipient vehicle, not near the battery. The point of this procedure is so that when a spark is created by attaching the black cable to the bare metal spot, that spark will not ignite hydrogen gas that the recipient battery potentially might create.

In the case of 2G Prius using the dedicated positive jump start terminal, it doesn't matter whether you connect negative or positive first as long as you get the battery polarity correct, and finish hooking up the cables on the Prius side, not on the donor battery side (to avoid creating sparks near a battery).

 

Thanks for the info. I bought a CTEK XS 3600 battery charger CTEK XS 3600 12v Battery Charger, but I've been too chicken to connect it up yet, and instead I have resorted to driving the Prius around more than my previous car.