12 volt dead

it can be. how old is it? it might not be worth investing in a charger.

 

that's not too old, might be worth trying to charge. otoh, it may only have a year or two left. i think you can take it to auto zone for a free charge and test.

 

sure, use the jump terminal under the hood. don't cross pollinate it.

 

you can't. the battery is in the back. if you cannot reach the front, use the key to unlock the drivers door.
check the owners manual on how to manually open the hatch. climb in back with a flashlight and necessary tools. open the hatch and put the jumpers on the battery.

 

If you are concerned that the 12v battery is totally dead, you can disconnect the (-) cable with a 10mm wrench. If you connect the charger to the jump points, it should be adequate to power up the electronics to let you start the car. Remember, the prius 12v system only supplies power to the electronics and control circuits of the car. The HV battery supplies all the power for cranking the engine. Once the ca ris powered up, the HV system converter will supply the 12v system through a converter. You should be able to drive the car to get it home or whatever.

I think I'm going to try this with my own 2007 tonight. My son bought one of those pocket sized, new fangled polymer chemistry jump batteries. I think I'll try disconnecting my 12v, (leaving the trunk open, just in case, lol) then connect his pocket jump to the car at the jump terminal and see if it's good enough to get the prius powered up.

 

the battery terminal connections, and especially where the negative cable is grounded to the body. they need to be tight and clean.

 

You can use a set of jumper cables, a pocket jump battery, or even a charger to apply 12v to the underhood jump terminal. Connecting to the underhood jump point will power up the 12v system, which is really all you need to get the electronics fired up. Once the electronics are "on" you should be able to start the car. Sometimes a dead battery may be a high load on the "jump" power supply and draw it's voltage down. If this is the case, it can be prevented by taking the negative cable off the cars 12v battery.

 

Absolutely but it can be tested after a good long slow charge to see if that revived it.

I've used one to power the 12v system via the under hood jump points on my Energi while (very carefully) swapping out the 12v battery so I wouldn't lose all my settings. Much caution is needed so I don't recommend this method to most folks.

 

Guys I have a question regarding the 12v battery.

I got my first Prius (06 model) a few months ago and the Toyota dealership recommended I change the 12v battery soon.

Yesterday I had it tested at a shop I was going to purchase a battery from but that guy said that the battery is in good condition. However, I tried testing it myself by pushing the on button, holding down “info” and switching lights on and off 3 times and then accessing that menu.

The battery indicated 12.3 V, after pressing the ON button again and went into accessory mode, the battery stayed at around 12.0 V before dropping .1-2 but when I turn on the headlights it drops below 12.0 and after about 30 seconds or so it goes down to 10V and I just stopped it there.

Does this indicate that the battery needs changing or is it rather an indication that there is a different electrical problem? Like something putting an unnecessary load on the battery.

Thank you.

 

At minimum the battery needs to be fully charged.

Once it is fully charged, if you should conrtinue to find that after 30 seconds with the headlights on, the battery voltage drops to 10V, then replace the battery.

 

I would go further to say, in the headlight test above, if the voltage does not stablise above 11.0 V and can hold that voltage for 5 min or more, then don't bother trying anything else. This test shows the battery is not holding a charge, so the only thing you can do is replace it.

 

It is possible that the battery has sulfated enough that it is not trustworthy to hold a sufficient charge now. If you can rejuvenate it I would be watchful about its condition and consider the battery carefully before taking any long road trips or leaving it parked for extended periods of time.

Did you use the switch under the steering wheel to disable the keyless entry (SKS) this last time? Or does it not have keyless entry?