Question about loss of acceleration

I'm a newbie to this site and owning a hybrid vehicle. I just bought a 2001 prius. When I bought the car the seller told me that it had a bad HV battery. He was selling it pretty cheap and I figured if I had to buy a new rebuilt battery I would be ok with that. When I got the car I had all three warning lights lit up, the main, the car with exclamation mark, and the PS. I replaced the 12V battery with the yellow top optima battery. I no longer have the PS or main light but I do have a check engine and the car with the exclamation and the little exclamation mark inside the triangle (I can't remember if they were there initially) The problem I have is that for the most part the car runs fine but every once and awhile the brake light will come on and the car will not accelerate properly. When it does this it will drive but it sounds like it is revving and the car may only go about 13mph. If I turn the car off and then turn it back on the problem goes away. I don't have that much car experience but I'm a fast learner. Since I've owned the car I've changed the spark plugs, cleaned the throttle body and MAF sensor, changed the rear brakes and a rear wheel bearing hub assembly. I have done these things from books I purchased and this site. I've read a couple post similar to mine but it seems like nobody comes back and says that their problem was resolved. So hopefully somebody will have some ideas. Some of the things I've read that I thought about were traction control problem, or main battery.

 

So to update my situation I had the codes read at autozone for free and they came back with a P3006, Fuel air metering, Auxiliary emission control but when the guy went to print it out for me he said the computer was giving him a different code P3017 which if I remember correctly was weak battery cell 7, and something about the main relay. He stated the P3006 was the correct one to go by. I was thinking about thinking about replacing the individual HV battery cells that are bad but everything I have read says not to do because it will just cause more problems later on. I was wondering if other cells continue to go bad how long does it take weeks or months or a year later?