Emergency dash lights on after 30+ m, trouble accelerating, stop driving 1-2 days, lights are off

Hi all,

I have a 2005 Prius with just under 200k on it. For the last several months, when you drive it for more than 30-ish miles, the emergency lights come on the dash (triangle of death, brake system warning light, check engine, and the hybrid system warning light on the panel screen). If I have the ac on, it will eventually turn it off with the panel screen message "ac off". I definitely notice that it struggles to accelerate. It's also maybe louder than normal, which lately is pretty loud. If I pull over and turn the car off, when I turn it back on, the message "There's a problem" comes up on the screen. (If only it would say "There's a problem....AND IT IS ______". But, no! That would be too easy.)

During the most recent incident, I was on the highway going 55 mph and then all of a sudden, the speed started to drop rapidly. It didnt matter how much gas I gave it, the speed was falling steadily. It got to 25 mph in a matter of seconds. Luckily I was able to pull off the road and bring it to a stop. I turned off the car, let it sit for 15 minutes, and then drove on side roads before getting back on the highway. The lights were still on on the dash, but once I got back on the highway, it was able to accelerate and sustain at the speed limit. The ac still wouldnt work. Two days later, after not having driven it, I turned it on and the dash lights were off.

This has been happening over and over again over the last several months. When I took it to a mechanic––the dash lights were of course off then––there were no diagnostic codes. He said it "might" be something with the inverter, but didn't elaborate, said I was fine to drive it "as is" and that I should come back if it happens again. It did happen again, and again. I'd like to find a better mechanic, but if the car isn't showing any error codes, how can they even help me?

If it's the hybrid battery (or really anything more than like $600), it wont be worth the money to replace it - it's more than the value of the car at this point....

Any ideas on whats happening?

Thank you!!!
S