Considering 2010 Prius, 12v question

The 12v battery is probably bad at those loaded and unloaded voltages. I would have it tested free at most auto supplies and then replaced if it fails. You could try a maintenance charger like a Battery Tender Jr ($28) over a several day period. The 12v agm battery might be $225-$300 depending where you buy it. A Toyota 12v would be at the high end but could last 7-8 years and is a good value over the long run.

The 12v battery will likely be the least of your problems and the cheapest to rectify. The car's mileage would tell the story better. If it is much over 100k miles, I would run. You may have brake booster, head gasket, inverter and or high oil consumption to deal with during your ownership. Each is well over $2k although the inverter may still have a special extended warranty under some failure modes. The egr system is a problem as well with clogging of the egr cooler and intake manifold a $800 job at a dealer.

Notice I did not even mention the thing most used Prius buyers worry about, eg the high voltage battery. It often makes 175k-200k miles and is also in the low to mid two thousands.

The car might be worth a gamble at 40k-50k miles but only if the price left room for one or two of the bigger repairs. This Prius is one of the most complex vehicles ever made and shows it when bigger repairs are required. If reliability is important, consider a Camry (except 07-09), Corolla, Accord or Civic in your price range.

 

Neither of those numbers are good.
But the onboard diagnostic for the 12 V battery doesn't seem to be worth much either.
You should insist on getting the battery replaced and the charging voltage tested BEFORE buying.
That 12.5 number could mean that the charging system is bad.

 

$$$ down the road

 

saving gas cost a lot of money.

 

The 12v battery is under the mats in the right rear.

If you buy the car change the oil every six months regardless of the mileage.