2009 with P3000, P0A80, P0571 - intermitent 0% or 100% charge state and high/low voltage on a blade

Ye wise saints of PriusChat - first-time caller here.

Itermittently, but usually after startup, I've got error codes and reportedly no charge (0%) on the traction battery. Later, itermittently, it'll report 100%. One "blade" in the pack has low voltage during load and high voltage during recharge. I think I want to try and replace the two cells in that "blade" and install a Prolong charger, but before I get into that I thought I'd see if anyone has wisdom / ideas.

Background:
My 2009 Prius has 85k miles. I'm the third owner for about 2 years now, previous owner was a bit of a tinkerer but did not report replacing the battery pack. I don't drive every day, and usually it's parked for a week at a time between ~100 mile trips. In the past it has served as a generator for a sound system a few times (with a 12volt to 110V adapter) for several hours at a time (idling to recharge), which is probably not great. But there it is.

The problem:
~2 miles into driving on surface streets, I got the red triangle, VSC, and the brake warning lights on. I took it to a shop to read codes, but they couldn't figure it out and said to go to the dealership. I got my own code reader (codes and data below). The codes stayed cleared for a bit, but recently it seems to have gotten worse.

It itermittently, but usually, will light up and throw codes a few seconds after startup. The triangle, VSC, and brake system lights come on, the MFD reports traction battery at 1 bar, I get codes of P3000 (battery controller), P0A80 (y'all know that one, traction battery problem), and sometimes but not always P0571 (which is about brake pedal actuation). Dr. Prius OBDII reader app sometimes but not always reports a 0% battery charge for a few minutes while charging. After a few minutes the MFD reports moderate battery charge and I can drive it around, and it usually doesn't throw codes again until I park and come back to it later. But sometimes it will go to one bar on the battery and throw codes. The inverter coolant tank looks like it's pumping. It all looks good - until you look at the OBDII Dr. Prius readout.

When in park or steady throttle, it looks good except blade 11 reports consistently lower voltage than the rest.

Idle_or_driving by palmatum posted Mar 23, 2021 at 9:36 PM

What's strange (to me) is that when the regen system kicks in (take foot off the gas), blade 11 will spike up in voltage above the rest. Sometimes then Dr. Prius will report 100% charge state after this happens for a while, and pack voltage looks really high.

Regen by palmatum posted Mar 23, 2021 at 9:36 PM

Regen2 by palmatum posted Mar 23, 2021 at 9:36 PM

When I go back to steady throttle or parked, it looks like just a low voltage on 11, but high-ish voltage all round. Sometimes the 100% state of charge reading persists:

Idle_after_regen by palmatum posted Mar 23, 2021 at 9:36 PM

I haven't checked the 12V battery voltage, and I intend to do that just in case there's something strange there. It seems like "INF subcodes" would be useful ( Code P3000 | PriusChat ), but may be hard to get ( Subcodes Reader | PriusChat ), so I'd love to hear of a cheap way to get these. Could it be the high-voltage fuse is blown? ECU bad?

What I think is going on:
I think that blade 11 has a bad cell and/or has some problem with the wiring. I think this is messing with the controller to make it think it needs more/less charge than is necessary/appropriate for the rest of the pack. Alternatively, the magic of bad battery chemistry is generating really high voltage on the regen brake charging that could be damaging the controller / batteries.

I think the P0571 also gets tripped because that's suposed to trip when there's low voltage on both pressed/released brake circuits for disabling cruisecontrol, and all these errors usually happen as I'm leaving a parking spot with lots of brake actuation. During cruise, cruise control interrupt works fine.

My plan:
I am thinking that I should read more about individual battery module replacement
( Gen II Prius Individual Battery Module Replacement | PriusChat )
and prepare to attempt swapping the blade 11 modules. When I do that, I intend to install a Prolong charger harness and clean the fan. I've got my sockets and HV 00 gloves, but haven't ordered batteries/harness yet... I don't have a lot of flexibility for when/how-long I can work on this at a time, so I'm trying to batch the repair attempt into one day.

If that doesn't work, then I figure it's the battery controller that's bad.

Does this sound like a good idea, or correct? How else can I diagnose this? Any ideas? Any wisdom?

I haven't found any posts in my searching that exactly resembles this problem, but would appreciate it if anyone has seen a post on here that's more similar. The most similar ones might be these:
Lots of codes - need wisdom | PriusChat
Code P3000 | PriusChat

 

Cool. I'm excited to crack this unit open and see if swaping the two modules in block 11 fixes it. I suppose having the prolong system ready and installed will make it a lot easier to balance all of these when re-assembled.

I'm looking at the price for harness or the Deluxe package, and I'm seeing that this has some pretty good resale value. I think it might make sense to buy the package outright and see if I get lucky with the swap-a-module strategy.

I've been procrastinating this but took it out for a drive today:

Regen3 by palmatum posted Mar 25, 2021 at 6:30 PM

esh!

 

Module swapped, Prolong discharge-ready harness installed, and car works (freeway ~15min) without codes, Dr. Prius says battery "healthy". Yet to do Prolong re-balance, that's up this week.

But I have one little problem. Well two actually:

so... I got the battery re-installed and then realized I had two extra 8mm nuts with integrated washers. These look exactly like the bolts that would hold on the main connections between the orange high voltage cables that (I assume) run to the inverter.

• However, those nuts are on there. I dissembled the left bracket again, visually checked that I saw four of these bolts on the high-voltage connections (both the junction with cables from outside the box, and the one with the cables inside the box that you bolt the Prolong harness onto). All torqued to the spec I was told.
  
• I went through all the instructions I had printed out for this (Electron Automotive battery pack replacement, Prolong harness instructions) and re-watched Chris Fix's battery swap video. I don't recognize another 8mm bolt like this anywhere in the process. The bus bar nuts are 8mm but don't have the integrated washer, and I counted those carefully.

Anyone recognize where these are supposed to go? Maybe around the 12V somewhere?


Other observations, for the record:

• I pushed it and tried to squeeze one more trip out of the pack after taking the images above in this thread, and the car threw codes more aggressively. It got pretty bad, and went into that emergency mode where it cuts out the electric motor, had to clear codes and restart to limp home. I do not recommend.
  
• I would recommend buying extra plastic clips for the trim and fan. Several of these are now missing.
  
• I got confused especially because (1) I'm like that and (2) I had to stretch this over two weekends because I promised a friend that I'd have someone else watching me while I worked on the pack (shock hazard). I recommend more ziploc bags and a sharpie for anyone doing this ! Organization is a very good thing.

 

One other note, several trim/fan clips were missing before I opened it and torques seemed inconsistent. It seemed like someone worked on this pack before. The battery modules had blue sharpie across the foot, so I do wonder if the previous owner had swapped in a used pack without mentioning it.

 

Update, finished the discharge/charge Prolong rebalancing treatment. Due to work schedule I think I didn't hit true rebalancing for the first two three charges (stopped at a steady 239V), and the discharges sat for a couple of hours after finishing (with smart charger) before starting charges. The final charge sat at 241V for ~6 hours, then relaxed overnight before reading 230V 7 hours later. This whole process took 5 days, like 120hours worth.

The prius drives fine, it stays in blue green a lot. Mileage is hard to say, it's all been on surface street driving. Voltage looks good, all "blade"s on DrPrius app with bluetooth OBD2 reader within about 0.1volts of each other. Of course, no codes.

I think it's good? If it goes haywire, I'll definitely post on here.

For interested readers, here's what I remember being useful for the repair:
- Used battery module from hybridautomotive.com was ~$50
- Prolong discharge-ready harness was ~$150
- Prolong charger/discharger was ~$700
- Two torque wrenches (1/4" 20inlb to 200inlb, and 3/8" 10 footlb on up), each ~$25-35 (ebayor Oreillys)
- 3/8" socket set (at least 8mm to 14mm) and extender/adapters (1/4" to 3/8" for the small torque wrench!) ( walmart or Oreillys )
- A cheap Ryobi power drill/impact-driver with 3/8" socket adapter - this is not for power, just for turning lots of little 8mm bolts before finishing with torque wrench
- You might want to buy a trim clip pack for a gen2 prius, a lot of them broke and I didn't replace, so a fan duct might be missing a pin ....
- Instructions - I used both the Prolong (2004 – 2009 Toyota Prius Plug-and-Play Car Harness Installation Instructions | Hybrid Automotive) and ElectronAutomotive ( http://bit.ly/PriusHybridBattReplace is the link from the ChrisFix video ) for the torques / battery details
- Safety glasses for eye protection (just in case), and nitrile/"rubber" gloves for reducing skin conductivity and comfort
- A friend standing by! Useful for conversation, advice, but also for 911 in case I get zapped by 220V

Y'all be careful out there.