Nexpower/Project Lithium Battery Issue - Blade #12 Failure?

Background:

• Bought the car in January 2023 with 218k miles. Pretty good condition overall. After testing, the traction battery was on its way out, so I looked into the ProjectLithium batteries. This is my first Prius, but I've learned a fair bit about them over the past two years.
• I installed a NexPower first batch V2 lithium battery in July of 2023. The car has been driving great since then.
• Occasionally the dash display fails to light up, but this usually resolves after a day. I believe this is related to the combination meter and unrelated to the present issue.
• On 8/7/24 I replaced the 12v auxiliary battery because I had deduced it was the cause of a recent no start, and an issue I had in January 2024. That battery was 6 years old.

The present issue:
On Friday 8/9, I drove to my work (10 miles, mostly highway 55mph) and it drove fine. When I left in the evening to go home I stopped by a friend's house briefly (about 1 mile from my work) and left the car on with the AC on while I talked with him. The engine never shut off during this 5-10 minute chat which seemed a little odd. I then left and began driving home. As I started accelerating after a stoplight the display beeped and said "Problem" and showed a red symbol, and the HV battery fan in the backseat shot on at high speed. The car drove but seemed to have no acceleration power, so I limped to a nearby gas station. I plugged in the code reader and checked Torque and it showed a 1.2v reading difference between module 12 and the others. The SOC also dropped randomly from 60% to 30%. I turned the car off, waited a minute, and then turned it back on and the issue remained. I switched it into drive and it could still move, but in limp mode. I moved it to the side of the parking lot and then parked it again. The module voltage difference had gone back down to a normal level (0.1-0.2 difference). I thought I would try clearing the code and see if it would let me get home. So I cleared the code and immediately the HV battery fan turned off and the car seemed to be acting normal. I test-drove it around the parking lot a bit and then decided to drive home. I thought it might just be a fluke because I recently replaced the 12v aux battery a few days before (although it had driven fine since I replaced that). I was able to drive all the way home fine (10 miles) and then as I turned onto my street I tested a quick stop and then hard acceleration. After the hard acceleration, the car threw the error, fan on, and lost all acceleration strength. The SOC dropped from about 55% to 30%, then after a moment began rising rapidly 1-1.5% a second until it reached 100%. I parked it and then switched to the Dr. Prius App and received the following reading. Note that Module #12 has double the delta voltage and resistance of the others.


The codes the system provided both times were: P0A80 and P3024.
At no point during either issue was the HV battery temperature outside of range.

Today, Sunday 8/11, after letting the car sit for a day and a half, I went out to run some more tests. When I turned it on it still had a fault code, but this time the code was P3022 and P3000. I cleared that and the car seemed to be idling normally as I watched the stat readouts with the Torque app. I then switched to the Dr. Prius app to see what those readings were.


Note that module #12 is showing yellow.



Once the car turned the engine off and stopped charging, #12 was still the highest voltage reading, and the delta voltage on it was also 1.70, compared to the others 0.53-0.59. A few seconds after this picture was taken, the car threw the error again (only P3022). I wanted to try a driving test, so I switched to monitoring it on my tablet for a larger screen. I cleared the codes, got everything connected and loaded up the Dr. Prius app and while I was still idling in park with the engine off, it threw the code again (only P3022) - turning the fan and engine on. The following picture from my tablet is directly after this.



All of the Sunday tests were taken while idling in my driveway. I never actually drove it anywhere. I haven't driven it anywhere since I got home Friday night.

I have contacted Jack at NexPower and now come here for suggestions and solutions. Are there any other tests I should try? Are these all symptoms of a bad #12 blade, or something else?

All help is greatly appreciated. Thank you in advance!

 

Thanks for the responses, everyone!

Today I took it apart and checked all the nuts. They were all tight and there was no corrosion anywhere except for a very minor amount on the main negative terminal wire, but not the contact portion. I inspected all of the blades and they all looked good - no signs of bulging, burning, corrosion, wear, etc. Unfortunately, I did not have my meter to check the voltage of the blades, so I'll do that another day.

Shoutout to @jacktheripper for superb customer service! He had a new Sodium V3 shipped out to me on Monday and I received it Friday - just 7 days after the blade 12 failure. I installed the pack and did a basic test drive and all systems seem to be working properly. I will do a more thorough test tomorrow.

 

I can't speak to whether he "knew" or not. I was pretty confident that everything was going to be tight because I know I secured them well when I installed it. I do live on a bumpy driveway though, so anything is possible.
Either way, I appreciate his swift service.

I don't think it's a prototype version, as it doesn't look like the pictures of prototypes that I've seen.
So far it seems like the v3 isn't giving quite as much "oomph" as the v2 lithium did, but I've only driven about 70 miles so far. Hopefully the computer will learn the new battery and use it more soon.