I have an intermittent issue with my 2008 Prius. Now and then I push the Power button, the dash flashes like a normal start and then everything goes dark. Then the CD player resets (you hear it moving) and the the car starts as normal. The clock has been reset to 1:00 and radio memory is lost. Less often, is a loss of power on shutoff. Today I stopped for gas, pushed Power to shutoff the car and it did not go through the normal shutdown. Just abrupt power loss, power windows stopped working, time reset, radio memory was ok. I could immediately go into auxiliary mode and had no problem starting. I think this has been going on for awhile. I recently replaced the 12v battery after having more 'normal' power problems. Shortly afterwards, the car was dead and the dealer said a low battery in one of the FOBs pulled down the 12v. FOB battery was replaced but I'm left with this issue. I don't think the problems are related but who knows. I haven't seen any reference to a similar problem. I'm loath to take the car in because it will be fine for days and days so odds are the dealer will not find anything. The problem is a bit disconcerting because I figure eventually whatever is failing will fail or, almost worse, it is just an intermittent electrical problem that will annoy me for all time.
First, check to make sure that all the batttery connections are clean and tight, including the bolt going to the body. Check the 12V: Entering Maintenance Mode (aka 12V Battery Check) without Switching Headlights ON/OFF | PriusChat Report back the three numbers you get. If you have the SKS system, then you can turn it off with the button under the steering column. If your key fobs are close enough to the car they can ping back and forth, which does increase drain.
The battery connections were rechecked at the dealer. I read 11.3v after the car was sitting a couple of hours, 11.8 after use.
Or, try giving the battery a thorough boost charge from a plug in charger, one with a pulse type output if possible. I also would like to see the voltage with the car on, to make sure the 12V system is getting up to its proper output. Is there any type of aftermarket electronics installed?
Nothing aftermarket. When I turned the car on, voltage popped up to 12.0. Guess I can bring it in and have the dealer check the battery again. What is odd, and I will double check next time this happens, is that the wipers/lights/etc aren't slow/low as they were when the old 12v was on its way out. Plus this is so random. Sometimes happens after car is sitting all night but sometimes after a drive. Today it happened on power off, almost like a system crash vs. graceful shutdown. I like your QTH and farm. de kd2mx
I would say this looks like a shorted cell situation, since the voltage is about 2V low. In that case, there is nothing to be done but replace. The 12V charging system can overheat trying to bring that battery up to 14V, so you may be seeing other consequences as well, like low MPG's.
Like jc91006 and nh7o said, that's definitely too low for when the car is on. The DC-DC converter should boost it to about 14 volts, so definitely sounds like something wrong with the battery. A shorted cell will put the DC-DC converter under a lot of strain, so I'd say avoid driving it until you get that battery replaced.
Thanks everyone....to clarify my voltage readings are low 11.x in Aux, about 12v in On, and ~14 in Ready. I wasn't clear on that. I have an appt at the dealer tomorrow and will see if they have a clue.
