Possible battery issue

I recently picked up a 07 Prius with 78k miles. I purchased it at an auction, the car had been in an accident and had light damage to the front end and was also said to have been in a flood too. So I've replaced most of the sheet metal on the car. I'm just waiting for one of the HID headlight Assy. I ordered to come in. Now I've owned a 2013 Prius plug in since 14 and I've put 300k miles on this car and absoulutely love it but it different in a lot of ways from the 07 I just purchased. Now my issue is that when I run the 07 Prius the battery levels seem to be very low, there's only two bars and sometimes three at best. My plug in would always be much higher. Now I drove the car a short distance the other day and when I was pulling back in my driveway the triangle light came up on the dash, and stayed for a short while. I shut the car off let it sit for ten minutes and started it and it was gone. Is there a battery issue with this car or is it because it sat without being run for a long time, if so will it come back to having a normal level or charge in the battery or is it shot or maybe some other issue? Any ideas on how I can find out what's going on with this car? Thanks, I look forward to hear some of your input. Also I haven't seen any evidence that the car was in a flood so I'm not sure why it was listed that way.