Dead 2012 Prius Plugin, NOT 12V battery?

Hi:

I have a 2012 Prius Plugin 180K miles, no known problems. Yesterday I started it to leave work and it ran for maybe 2 seconds, then went completely dead - no power at all (lights, door locks, etc). Tried to jump with a battery booster - no effect.

Returned this morning to check the 12V battery - initially it read 4.6V, so figured I would need to replace, based on other posts here. Removed the positive terminal connection and went to the negative and found it quite warm - hot even. Left the car to check with a dealership about whether this was likely a battery replacement or something else (they of course said tow it in). Returned to the car 30 min. later - positive terminal still disconnected, negative connected - but it was no longer warm. tested the battery again - read >12V. reconnect the positive terminal to car - decreases to ~6 volts.

So the battery seems good but I'm guessing there is a short somewhere> Negative connection to cable and cable to body looks very sound.

Any suggestions to diagnose further, or should I have it towed in?

Great forum, by the way.- I've used it often.

Thanks

 

Thanks for the responses.

Prior to these responses and following advice from elsewhere, I checked for "parasitic draw" - checking for current flow between the positive battery pole and the cable that connects to it - and that was less than the 50 mA that would indicate a drain.

Which maybe leads me back to the battery? I have a 2010 Prius - would it make sense to take the battery from it and see if it revives the dead 2012 PIP? I'm not sure if that is the same battery as used in the 2012 PIP. If that worked then recharge and test the old battery or just replace it?

 

It WAS the battery. I removed the battery and took for a load test. It had just enough charge to fail in a single test, so bought a replacement (Interstate), installed, and everything appears to be peachy. The dealership had a slightly cheaper price for the battery, but they did not suggested a load test when I asked (recommended that I have the car towed in instead) while the Interstate staff gave good advice and performed the test - so well worth rewarding that.

Thanks for the advice and saving me a tow!