Battery problems when warm

So I have had the typical P0A80 happen twice on my 2008 Prius with 193k miles on it. Each time it happened I went the reconditioning route and replaced the bad cells (I've replaced two so far). The most recent time I did it, everything seemed relatively normal for about 3+ weeks. Then one time driving home in the evening when it was relatively warm (50F for here) the dashboard lit up with all the tell tale lights for a P0A80 however the battery level did not drop and it drove normally for a few miles with the exception of the engine constantly running. A few miles down the road and then the engine started to rev up like it was trying to burn off excess energy from the battery but the level was still in the normal blue range. The car proceeded to do this and then it would accelerate without me even having to touch the gas pedal. There was a hill that I had to accelerate up and the lights (this was at night) dimmed like there was a big power draw to something, then engine revved up and then the lights went back to normal. I then pulled the car over and noticed that the fan for the battery and the engine was running full blast. I turned the car on and off a few times to see if the problem would go away but it did not. I happened to have a scan gauge on hand and all it gave was a P3011(battery block one is weak). I cleared the codes and I drove the remaining 8 miles home with no problems. When I got home the HV battery did not feel warm at all to the touch nor did the engine feel exremely hot.

I didn't touch the car for a few days then I continued to drive it short distances with no problems for another couple of weeks and I had just assumed maybe it was some weird fluke or wire not properly making connection. The code has come back multiple times and occurring more and more frequently however it only happens when the temperatures are above 35F-40F and is much less severe (drives normally aside from not using the battery to accelerate, I get roughly the same MPG, only the battery fan comes on). If the temperatures are above that range it'll come on if I drive more than 15 miles in a day. If its below those temperatures it seems like I can drive as much as I want. I even drove it 100 miles in a single day when the temperature was 30F without the problem happening.

I've taken the battery out and tested the voltages when it was 40F and they are all withing .02 of each other.
I took it to get the codes pulled at Auto Zone:
P3011
C1241
C1259
C1300
A remarkable thing about this car is the 12v battery has never been replaced since we bought the car in 08 from the dealer. Could this be causing the problem? Other than that I am completely lost about what could be causing this.

 

The first time around I did a load test on the one I suspected was wrong with a light. Second time around I did not load test any of them. The most recent time, I turned the car on without running the engine, blasted some music with the lights on and drained the battery some as a load test and they still all remained in the same range. I've heard of balancing them but I haven't done it any of the times.

No I do not. When the codes come on I can hear the fan running and it sounds normal to me but I'll take apart the fan and check to see if there's any gunk in it tomorrow and also run a test on the 12v.

 

Okay. So I finally got time and warm weather and I checked the fan. Compared to pictures I saw online there was pretty much no gunk in the fan. I still cleaned it out with no change. I tested the 12v battery and I was able to get it down to 9v with the front defrost, rear defrost, and lights. So I then went ahead and got a new 12v. After that I was still only able to drive it the normal distance (around 15 miles) without the codes coming up. The car also revved the engine up like it was trying to burn excess energy and I would get around 60mpg when coasting and it would not use the regenerative braking. The engine fan was as well as the battery fan were on full blast. The problem with the engine revving up however has only occurred twice. Once when it first started happening and the other time, today, when I had just replaced the battery.

From here I am completely lost. I can try to check the cell voltages at a warmer temperature since the last time I checked, it was cold. I would prefer not to take the car to a dealership since it is at 194,000 miles now and Id prefer not to spend $4,000 on a new HV battery.

 

That is about a 5 hour drive from me. I've been looking on eBay and there's someone selling in Ohio that'd only be 3 hours away. It may be a few months before I can get time and funds to drive somewhere and get a battery or pay $100+ for shipping. I'll just have to see what comes up when I have time if no other solution presents itself. $800 is about the max I want to pay for a used battery for this car.

 

I'll make sure I get at least a one year warranty and buy from a more esteemed person If I go that route.

Inverter pump seems to be working well and has flow.

Since it is throwing a P3011 battery block 1 is weak, can I just replace that block and see if that resolves anything? I happen to have 2 fresh cells on hand that I can use. Where is block 1 at? is that the side closest to the fan? and is it just one cell or two?

I also have not ever balanced the battery. It would make sense if it was saying block one is low since I believe I replaced block one entirely. (if block one is closest to the fan vent side and every other cell. Should I try to buy some balancing equipment and balance the whole pack? I could also try to move those replaced cells around in the pack to see if it triggers other codes saying different blocks are weak.

 

I fixed the problem! Since I do not have any balancing equipment, I just switched the two I replaced out of the same block. I think the two being in the same block caused the two to behave differently from the others, especially in warm weather for some reason. That explains the P3011- "Block one is weak" By switching them out and putting them in other blocks it balances them out with the others. I do realize this is a temporary fix but I am going to drive it as long as it works and hopefully by the time it stops working it'll be summer and I can get equipment to properly balance the battery. Thank you for the help!