Overcharged HV modules?

So I have a strange thing happening. I have the P0a80 code with the Red Triangle of Death (RTD), and after checking the HV cells, each of them is registering in the range of 8.31-8.34V. I've never seen them this high, as they have generally stayed in the 7.84 to 7.88V range. One of the cells is coming in at 8.24V, but the rest are right in the above range. Can this be right? I have a Gen II, 2005 Prius and am in Tucson AZ.

So, a little background. About a year ago, I had the RTD show up, and after reading all of the posts on PC, I decided to try to fix it myself...though I am far from skilled in this area. Patrick W even offered to help, but I thought I'd give it a try myself before bothering him too much. Well, 2 cells were clearly bad, so I ordered replacements off of Ebay, charged them to be right in the middle of where the rest were at ~7.86V, installed them and voila...the error went away and I drove trouble free for 9 months or roughly 12K miles.

About a month ago, I got into a fender not paying attention and banged up the front end pretty bad. The body shop replaced the hood and front quarter-panels, but as far as I know, everything else was ok...I drove it to the body shop 5 or 6 miles with no error codes, etc, so it seemed that the car was mechanically functional. After the body shop fixed things up (about 3 weeks), I drove the car home and almost immediately got the RTD again. I figured that the 3 weeks of inactivity may have wreaked havoc with an HV module or 2, so I quickly tore it down again and tested the modules. This time I identified 3 modules that were bad, and replaced them from Ebay modules that all tested good when I received them. After charging these replacements to the mid-range of the other cells (~7.86), I put things back together and drove it for a while. Even though the RTD light went away, I had the strange behavior of the car over-idling, the HV battery going from solid green to 2 blue bars and then back up again within a few minutes of driving, and also not shutting off at when stopped and charged. Strangely, the heater also does not work.

So... a few questions to the PC studs:
Can the voltage readings be correct on these modules? This seems very high to me.
Is it possible my inverter is screwed up, was damaged by the accident? It certainly looks ok and didn't seem to be in the "crush" area.
I assume the heater not working is a different issue...agreed?
At no point in either the first or second HV rebuild did I go through the steps to rebalance the modules, is this my next step, or does anyone think there are other things at play like a damaged computer or inverter?

Thanks in advance for any advice...

 

There are 139K miles on her. I believe the inverter coolant pump is working...I think I can hear it running and I don't have the fail code on for it.

 

Thanks Greg, It's a good idea to run through and load test the cells and see if any are substantially out of whack.

 

The 12V is good and not dis-charged... it's a new Optima and I've load-tested it.

On the HV battery, I'm just measuring the DC voltage with a voltmeter directly on each module. Perhaps I need to invest in the Mini VCI. I can't see where my ODB scantool shows me the individual battery module loads and min/max.

 

It's a Klein tools voltmeter, I think it's pretty good. I tested it on a few other batteries I had laying around and I think it's fine. The answer to the green bars question is yes...8 green bars...maxed out. I have to believe something is causing the charging system to keep charging when it shouldn't be. I hope these modules are still good, I'm going to drain them down to 7.5V and recharge them back to 7.87 and see if they hold there.

 

Ok, an update on progress. I load tested each of the units using my charger and an old headlight...one of the modules came back as slightly out of tolerance from the others. So I replaced it with a good module. I then charged or drained each of the units back to 7.87V and put the pack back in just to test it. The RTD went away when I started it up, but immediately, the gas engine idled high. I took it for a 1/4-mile drive to see if it would balance out, but the idle remained very high, so I quickly returned home. Once again, each of the units was charged up to 8.11 or 8.12V (uniformly). I let it sit overnight last night and the modules generally held their charge. I called a local shop that specializes in Prius, and he said he couldn't help...that my HV pack needed to be rebalanced and that was definitely the problem. Does anyone else have an opinion that a rebalancing IS the problem?

 

Great thought JC...Last year the Toyota dealership said the CARB warranty had just epired, but maybe I should do a little deeper digging.

 

I agree...perhaps this one is just going to be beyond me...