Possible battery problems , which one? plus engine lights

Hi all,

I've got a topic that I can see has been covered many times, and all of the answers have been pretty educational!
So my car is Gen II, 12 years, 164,000 miles, has been a very low maintenance car so far. The 12v is 3 years old, optima yellow top. Recent oil change, fluids all full, and I believe I can see movement in the inverter coolant tank. The problem is that 4 lights came on a couple days ago: RTD (red triangle of death) VSC, (!), and also the more common check engine light. The main symptom up until now was that upon starting, the few blue bars that were left would turn to 1 purple after a couple of minutes of driving, then the battery would go all the way back up to full green in 3-4 minutes. After that all is normal. Except for today, I started having acceleration and power problems. A slight hesitation when accelerating from stop, and some power issues (to put it mildly) when going up a large hill on my commute. Almost didn't make it to the top.
The battery diagram on the screen on my most recent, and thus far longest trip this week (30 min each way) was full green most of the time which is really unusual. The energy flow according to the display screen is also strange. The power is almost only going toward the battery, and never away from it even when going up hills. It's as is the battery is only being charged and not drawn from. The mechanic at Meineke who changed my oil today also found a couple of inches of water in the spare time well which I managed to drain out. He suggests water damage to the HV battery.
I've checked out the 12v battery using the diagnostic screen, this morning before driving, it was 11.1 V before 'ready' mode.
Meineke couldn't give me any codes to work with. I'll probably bring it to a garage in the next couple days anyway, but I wanted to check in with y'all to hear some opinions.
The good news is, got my inspection sticker last week before the lights came on (and after the dashboard display started coming back on regulary, there's that too!)

 

UGH. Thanks for weighing in. I'm definitely going to get the codes read soon, as well as test the 12v tonight. If the car is otherwise solid, body-wise, and it's been well-maintained, do you think this 12 year old 164.000 mile would be worth the new traction battery? Or time to just move on? I've kind of always wanted an Outback or Forester...

 

Good advice man, thanks for that. I've decided I'm going to bring it to a Prius knowledgeble guy tomorrow, and hopefully he'll give me a solid diagnosis. I hope to fix it because thinking about it, I like the car and it's been otherwise very reliable and it's in fine shape but for some minor quirks. I'll keep you updated!

 

So update on the battery, a mechanic confirmed the Replace Hybrid Battery code, and I had all the classic symptoms according to a coupe youtube vids. I used Hybridbatterdoc that I found on ebay while shopping for a used battery. I talked with a real person each time I called which felt reassuring and there was 402 reviews, all positive. No negative reviews. So I set up an installation for 1,000.00, used battery with one year warranty. The guy was at my house in a couple of days, had the old one out and new one in in under 40 minutes. He was able to tell me about every singe part and symptom I asked about. The cars runs good as new. He noticed that the cooling fan vent wasn't fitted properly to the bottom of the battery so he suspected that the battery wasn't getting cooled properly and that's maybe why it died. But who knows, it could be just because it's 12 years old. So, not as big a deal as I thought, and here's hoping the 'new' battery will last me at least a couple of years, if I don't decided to trad or sell first.