4 warning lights- trouble running- advice?

I have a 2007 Prius with about 150K miles. This morning, no warning lights were on and I drove about 20 miles no problem. Later, when I turned the car back on, the Master Warning Light (triangle of death), yellow brake warning light, VSC light, and engine check light were on. The automobile outline with the exclamation (!) in the middle was on the energy monitor as well. I looked in the manual and it said if the lights were yellow I could drive, so I did, and at first everything was normal, but after about 5 miles, when I would stop the car and try to accelerate, it would accelerate very slowly even with the pedal to the floor and the engine was loud. Once I got to about 45 it was fine, but getting there was difficult. When I drove up a hill, the speed decreased. The energy monitor showed nothing going to the battery, and the battery had one level left when I reached my destination. A couple hours later, I started it again and it charged the battery back up to blue while the car was sitting. I also took it for a test drive and it drove fine, but all lights were still on. I checked the inverter water pump (there was turbulence so it appears functional). I also tested the 12V battery. 11.8-11.9 on ACC with headlights off. About 14.1 with car on.

In short, symptoms:
-Master warning light, VSC light, yellow brake warning light, and engine check light
-Car slow to accelerate with pedal to floor, battery drained to one level while driving, no energy going to battery
-after sitting for a couple hours, battery recharged and drove fine, all lights still on

Any ideas on what could be the problem?

 

I am taking it in to Toyota tomorrow, will update when I know anything new. I did notice the fan in backseat (forgot to mention it in my original post). It is loud and noticeable; it wasn't before. Could that mean it is overheating? Do you know the difference in repair between an overheating battery vs. a failing one? Do both require replacement?