Battery balancing w/confusing results

A few weeks ago I purchased an 05 Prius with the scary red triangle on the dash. When I picked it up it had P0A80 and P3018 stored in the system. The guy I bought it from said that it would lose power every now and then but otherwise things seemed fine. Some diag at home plus a lot of help from this site led me to module 8 and a plan to replace/recharge the battery. I picked up some cells of ebay, a hobby charger and went to town.

I cycled each cell, replaced the 2 in module 8 and when it was all done I ran the cells in parallel for a little over a day. When I disconnected the wires all the cells sat at precisely 7.87 volts. I put it all back together and put it in the car. When I started it up the module voltage as reported through the Dr Prius app ranged from 16.47 volts (module 8) to 16.93. The Red light was still on but the others had turned off (apart from the one telling me its cold outside). The app said the pack voltage was 235.52 discharging at 5.57 amps, blade voltage 8.41 with a voltage difference of .46. I figured I needed to take a second look at my replacement cells so I pulled it all back apart. This time I had no codes stored in the cpu (and no CEL, just the triangle).

I ran the replacements through a cycle along with a couple others that had variance on the test, removed all the copper, soaked it in vinegar and brushed it clean. I also pulled the 12 v battery and charged it on an AGM specific charger (the previous owner had replaced it, but it was a little low after sitting for a few weeks. After the cycles I hooked it all back up in parallel. Once again they were all very close in voltage (less than .03 volt swing, I didn't write down where they landed this time but it was higher than last time.

I put it back in the car last night and this time all the lights were back with the red triangle. This time it said the pack voltage was 224.61, blade voltage 8.02, voltage difference .22 volts. The modules ranged from 16.2 to 15.98. This time module 8 (my original suspect) was at 16.09 volts, the others were all over the place. When I ran it this time the app reported the battery temp as -86.8 F. I hadn't had that issue previously. The cooling fan runs non stop and I do see movement in the inverter coolant. The codes that I initially saw still did not come back on.

I obviously need to take a look at the temp sensors, what else am I missing? I don't understand how the voltage can be even when I assemble and then be so far off when running. Are there other diagnostic procedures I can try when I rip this thing back apart? Am I better off accepting defeat and just buying a replacement?

Thank you for all the help I have already found on this forum and thank you in advance for your continued guidance.

 

I was able to resolve the temp issue when I located a loose connector. Fixing the connector also shut off the VSC light, but not the red triangle or CEL.

 

I figured it out!. I fixed the loose connector and took it for a little drive. Using my other code reader I was able to pull three codes created by the loose connector, when I cleared those everything went back to normal and it drives great!. I'm 1800 into a car that will save me a ton of $ on gas and super excited!