Strange electrical problem on shutdown

Hi everyone. I'm Moss and brand new to this forum. About a month ago, I began having strange problems with my Prius when I parked and turned it off: the power would completely die, and I couldn't start it back up. The first time this happened, I needed a jump; but the second and subsequent times, I could get the power to come back (one time by pushing the reset on the 12v battery). When this happens, I'd lose all my data (e.g. odometer, fuel consumption, clock, etc.). I took it to the dealer, who checked all the batteries and found no problems. When this problem continued, I took it back again, and this time, they moved the reset button that's near the parking brake, thinking I'd inadvertently pressed that button when engaging the break. Everything worked well for the past two weeks, until this weekend when the problem began again. This time, though, the Prius does not turn off when I press the power button (while pressing the brake down, if that helps). Rather, everything seems to reset again while staying on in accesory mode. The 12v battery seems fine, and the car's just a bit over a year old. I have no idea what is going on, nor does my dealer. Has anyone encountered a problem like this? Any advice? Thanks!

 

Thanks, everyone, for these quick responses! @Richard, I've tested the 12v, and it checks out well, as did the dealer with the same result. As far as I know, it's never been drained to empty, so I'm confident it's fine. When I bought her last July, I was required to also buy a starter guard to protect the batteries (as are all buyers here in Santa Monica), and I think you all are right in thinking it's the issue. Down near the parking break there's a small red button that is designed to shut off the power when parked for long periods of time. Pressing it for a few seconds will turn the power off completely, I gather, and the dealer's thinking was that I'd pressed on accident, so they moved it elsewhere under the dash. But I certainly haven't just started to do this now in the past month. Something's got to be faulty with this starter guard that produces the same effect as resetting the 12v manually. It's happened to me 7 or 8 times now, and I'm curious to hear if other drivers in Santa Monica have had this same problem. I'll take her in Saturday and ask them to take care of this.

 

Wow. I missed these threads in my initial forum search, so thanks dogfriend for pointing me to them. This is *exactly* what's going on with my Prius, and I'll report back Saturday after I take the car back to the dealer and ask that the starter guard be removed. I should have been more clear too that I bought a new 2008 Prius from Toyota of Santa Monica in July of 2008 too, so the 12v battery should be fine, as all the tests bear out. For what it's worth, aside from this problem I've had nothing but fantastic experiences with everyone there.