2012 Toyota Prius v battery?

I have a 2012 Prius V and tried to start it this morning as I was going on a trip with everything packed. All the lights on the dash went on and the emergency flasher light flickered several times. The front interior overhead light is dim. Could it be the 12v battery?

Well, that a possibility. Could need a recharge or its just getting old. Its 6 year old.

Yes, it could be the 12V battery–especially if it is the original one. 6 years is… pushing it… in many areas of the country.
But, the one detail that you omitted is exactly what happened when the engine didn’t start.
Did the engine not turn over at all, or did it turn over very slowly?
Or, did you hear nothing when you tried to start the engine?

I’d guess it was the 12V battery (which doesn’t start the car, but powers many of the computers and electronics). I’d also guess the engine did nothing, since it’s started by the main battery pack.