2005 Prius - We got lights, and we got shapes boys

Bought my Prius a few years ago. Ran great. Lots of wear and tear but all around solid.

Maybe a year after owning I got my first triangle of death and the car died on me. It was in super hot weather, and I had been sitting in the car with it on for a little while. In retrospect I'm thinking it probably had something to do with the coolant pump, but I'm not sure.

Had a mechanic come out and I think he basically just cleared the codes. It ran fine for a while after that but was dying every now and then.

Fast forward another year and my Prius hasn't been starting a lot of the time. I have to get jumps regularly. I figure its the AUX battery and get a new one and all problems seem to go away.

Fast forward again, another year, to now, and a couple of days ago I noticed that the battery in the trip info tab acting very strangely. It will start off very low or drain very quickly upon starting. It will go all the way down to the last bar. The car will also run like crap... very sluggish. However after running for a bit the battery charges all the way back up and runs fine. Interestingly though the battery literally goes from one bar all the way to full bars very, very quickly.

And then finally today I got all the bells and whistle while driving to school. Triangle, check engine, amber exclamation mark, and VSC. There was also a weird vent thing that came on in the back seat. I've since learned that this is vent for the main battery. The car still runs (I had to get to and from school), but obviously there is something very wrong here.

Now I just got the car serviced maybe two months ago, and I just got a new AUX battery less than a year ago, so I'm really thinking its an issue with the main battery which means doom for me as I can't afford that fix.

Anyone got any ideas for me?

All help much appreciated.

 

Update: I checked the AUX battery charge with a multi meter and its at 12.4V so now I know that's not the issue.

I also gave it a good ol hard reset by disconnecting the negative lead of the AUX battery and that cleared up all of the error lights. I'm guessing that just cleared the computer. Haven't driven it yet but when I turned it on it did the same thing as before and the trip info battery went all the way down to one bar. I let it run for a little while to charge it back up.

Haven't driven on it yet but will update when I do if anything interesting happens.

Obviously there is still an issue here. My guess is the main battery is just dying which is a hard sadface.

 

Nope never replaced the inverter pump. What would be the cheapest option to get this fixed?