Dead as a doornail

Do you know how old the battery is?

 

I would venture 12v -- I know, I know, but if it is truly the original -- it's the 12v.

 

You need to test the 12 volt battery after it has been sitting for a while, before turning the car on.
Whenever the car is in READY it charges the 12 volt battery even if the engine is not running.
Some people leave the hood ajar to they can test the 12 volt after sitting without opening the drivers door or starting the car.

 

Tests good? Electronic load tester is best, will check both the voltage and the Cold Cranking Amps. Many battery retailers will have such a tester. Is that how it was tested? In a pinch, an at-rest, car-off reading of voltage will give you some clue.

 

As Mendel said and Prodigy said. If it were me, I would leave it sitting for at least eight hours, then test at the jump point under the hood (a bit easier to get to then messing with the actual battery).

 

jump point under the hood you can't get a dam clamp attached to that dam thing the plastic is in the way #$%@ing jump point!!!! As for your problem if it's 6 months old it could be a loose clamp especially if the battery is not oem but bosch or others or if it way tightened to hard those are lead terminals after all.
I used a cut up hose clamp (cut screw stuff off use as sort of a ring shim) around the lead post to clamp in tight on the positive side, which was slipping took me a while to figure that out because that was a brand new bosch install pepboys did just a few weeks b4 the trip(only reason they installed it was to save me the sales tax on the core charge hehe ;-)).
While I was viewing the eclipse last year (in madras like almost 900 miles from home lol) I have not had 12V battery problems since. ;- )
terramir

 

oh no way to fix that gas problem if you pump it in slowly the 1st time it clicks you got like almost a gallon to go especially if you have a 14 1/2 yr old gas bladder in the tank. the gas gauge on the Prius is crap too needs at least 3 gal to register anything period. this car is the slowest fill of any of my cars and I had 2 fox body mustangs an f150 with dual tanks and a d200 75 dodge lol. that went faster at least if you want it full.
terramir

 

When the car rolls over? What...the car rolled over?

Open hood. Take cover off fuse box. Flip up red plastic cover. Thats the 12 volt positive post. Measure there with voltmeter.

With car off turn on the headlights on high beam with car off. What does the voltage read at that jump point?.

And the jump point is very easy to hook jumper clamps too btw. It has a metal vertical tab thats bolted to the jump bolt.
Its there to attach jump clamps. No plastic in the way.

 

Sometimes your volt meter will lie to you, you need what is called a "loaded circuit test" like mentioned above. An unloaded test will read battery voltage, a loaded test will show what it is putting out under load.

 

You must have a pos voltmeter. Who’s going to have an electronic load tester? I’ll settle for a voltmeter and a simple test first.

My 2 year old yellow top tested 12.63 sitting. With car off and high beams on it tests 12.10.

So that’s a .5 volt drop. If op reports a 2 volt or 3 volt drop or his sitting voltage is really low to begin with go no further.