Blank dash no power

How, exactly, did you check the battery? Battery checks are done first thing in the morning, after not using it overnight. Did you also check for loose battery connections?

 

I would at least find out where in your town stocks the 12 volt battery for a Prius.

 

Sounds like it's time for a new 12v battery. Just to be clear, the 12 volt doesn't crank anything. It just powers up the computer. Why it was running when you got back from lunch is a mystery to me. But once it was running, it would charge the 12V. You need to check it with a volt meter with and without a load and the car shut off. Might want to check again with the car running to make sure the charging system is OK, but that probably won't tell you much about the battery itself.

 

14.4 volts just means the car is charging it properly. you don't have to pull the battery, just put a volt meter on the jump point under the hood.

 

14.4 volts is the voltage that is charging your battery, not the voltage of your battery. Let it charge for a couple hours, it just needs to be ready, you don't need to drive it. (be sure it has enough gas)

And check to be sure the cables are tight at each end, it may be the connection, not the battery.

 

The most important measurement is before car is running. How old is this battery?

 

You don't need to pull the battery to check it just open the hood and take the cover off the black fuse box and under the red plastic cover is the 12 volt positive jump point. Test across that point and chassis with a volt meter first thing in the am before you start the car. That will give you its resting charge. I'm guessing its around 11 volts.
The car has probably been flashing the red exclamation point upon boot up too . Only flashes it for a second on the dash then goes away.

That's the only warning it will give you your 12 volt battery is crap.

 

Turn on car the pull fuses in bank c then turn off install fues in the right spots

Posted via the PriusChat mobile app.

 

Posted via the PriusChat mobile app.

 

I had two Prius do this and it stayed fix in both been years
It will sync computers

Posted via the PriusChat mobile app.

 

You can check the 12 volts at the cigarette lighter with the car off

Posted via the PriusChat mobile app.

 

It takes less than a minute to pop the hood and the cover over the fuse box and put a meter on the positive terminal and a bare bolt or nut.. As several others said, do it with the car off. Otherwise, you're testing the charging system, not the battery.