I have an '08 Prius with 10K miles. Twice it would not start, once in the AM after sitting 12 hours, and once 3 weeks later after sitting 1 hr. Both times I jumped it to another battery - but all I did was "touch" its jumper terminal and frame with a battery in another "non-running" car, and after it "sparked" upon connection I was able to start it immediately. It did not need to "charge" my Prius starter battery as in a non-hybrid vehicle. Before I "jumped" it I measured to voltage on the battery in my FOB, which was OK, and in the car at the terminal in the fuse box, which measured only 6.3V. After the jump it was double that - immediately. Based on my experience, I think something is intermittently causing the starter battery drop voltage, and this is happening with such intermittancy that the dealer told me that they couldn't find the problem, and have never seen this happen before. Of course they want me to bring it in when it happens - ha! I am certain that something is not draining the battery down to below a starting voltage since it needs no time to "charge" after it is jumped. I'd really appreciate any input - something that I or my dealer could check out. Thanks.
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.
My battery terminals show now sign of corrosion, and are tight. I drive 100 to 300 miles most weeks. "The most recent time that you jumped the car and got it to start, how long did you leave it READY?" - I am not sure what this means. But, the last time this happened I left the car off and unlocked for a little over an hour. There were no doors left open, and no lights visibly on in the car. (In my Passat I can leave the headlights on for an hour and still start my car, but in the Prius, when you leave the headlights on and power down the car, the lights automatically shut off. So, if the car is off, even if the headlight switch is on the lights are off.) I hooked the black jumper cable to the frame and just touched the red cable to the jumper terminal, it sparked, and the Prius was able to power on. Prior to that the FOB wouldn't even lock the doors. I think it must be something else, since the voltage I read on my VOM is so low when this happens, and then jumps right back up with an instantaneous remote battery connection (jump). Normally, when you jump a car you have to leave the terminals on the dead battery for a few minutes to get enough AH and V to turn the starter. I'm an OK mechanic on normal cars, and have an electrical background. This one has me stumped. Any other ideas? Thanks for your comments thus far.
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.
