My P0A080 fault code and battery rebuild

I have a used, mint 2006 with only 46,000 miles (PO was a little ol' lady) but I recently got the dreaded dashboard warning lights display and a car that instantly began running poorly (low power, ICE running much more/higher RPM) with the battery bars rising and falling much quicker than normal. I had also let the car sit with little use for several weeks.


As a long time PC member I knew my options:

1) Sell or trade in and let it be someone else's problem ($$$$$)
2) Go to Toyota dealer for a new battery installed w/3yr warranty ($3,000-3,500)
3) Get Toyota battery and install myself w/1yr warranty ($2,500)
4) Go aftermarket remanufactured battery by installer or DIY w/? warranties ($750-$2,500)
5) DIY repair and replace bad module(s) ($40-50)

I chose #5 because I recently purchased the car ($$$), I'm a DIY kind of person, and it came pre-installed with a grid charger wiring harness. It was installed by a family member of the PO but they kept the charger unit as they also had an aging Gen3 to use it on. I mention this because one thing being stressed about pack rebuilds is to balance the replacement module to match the others before use.

So, I purchased a prolong charger and discharger unit (sans harness) and tried to recondition the P0A80 pack via their 3 stage process but unfortunately it was DOA like I thought.

I watched a good video on pack removal and removed it myself. It's heavy but doable if you're in reasonable shape but if in doubt get a helper.

Taking my time, I disassembled the pack with caution. I measured each of the 28 modules, recording the values, and quickly determined #12 located in the middle 3rd of the pack was defective @ 1.33v lower.





The good news was the remaining 27 were within .01 or .02v of each other from the reconditioning treatment. I also saw the PO had replace #20 about a year earlier on the other side of the middle third segment.



Next I did a load test with a headlight bulb and results jived with the simple voltage test. So, I ordered one replacement module for $50 shipped.



The bus bars were heavily corroded.



So I cleaned them with the home-brew mixture of equal parts white vinegar and salt which worked GREAT. Then a mix of baking soda with distilled water as a rinse. I also used a wire brush as final scrubbing and cleaned all the wire and sensor contact points.

While waiting for the module's arrival, I was looking at all the recorded values from each voltage test and noticed that the outer modules were consistently outperforming those on the interior. It's been pointed out that there seems to be a trend with module failures in the middle of the pack with the thought being more heat/stress which makes sense to me. So I decided to rearrange the entire pack by moving the middle third out to the edges and vice versa. So the middle of the pack module arrangement now looks like this:






I haven't read about this "shuffling of the deck" being done before so I think I'm testing uncharted waters and hope it's beneficial. I then reinstalled the pack and began another 3 stage charge/discharge routine per prolong's instructions. This took me about a day to do each one. I did this in my garage with a large box fan also blowing on the battery (and me too). The pack, which was also running the hybrid fan, never got warm to the touch.





The car is running much better now! Previously, the ICE would still run for 10-15 secs at every stop even though the power flow diagram had no arrows! MPG is way up and the ICE shuts down at a stop like it's suppose to and no codes are being thrown.




I'm hoping this repair and periodic use of the grid charger will buy me one more year before going with options #2 or 3.

 

I'm going to follow the recommendations by prolong and see what happens. I know what doing nothing does.

Finding info on that has been somewhat hit/miss here but a good source can be found at prolong's site. Just read the short instructions on charge, discharge and load testing. Prolong Grid Charger Product Guides – Hybrid Automotive Other methods use home-brew RC chargers; search grid charging here on PC.

hope this helps

 

Yup, like I said it was somewhat a no-brainer since the heavy lifting (harness installation) was already there. I'll still keep the charger to use for periodic balance of the new batt when the time comes.

 

I figured someone's bound to have tried that before. Any idea if it's beneficial?

Good of time as any for an update because moments ago I put the battery on the grid charger. I am doing a charge on the first weekend of each month. It's been running fine and getting 45mpg highway in the summer heat with heavy a/c use (can't wait for some cool weather). Techstream shows all module pairs basically within .1v of each other. Next month during the Thanksgiving break, I plan to do the longer charge/discharge reconditioning process.

 

4 month update:

I perform an 18-ish hour balance charge at the first of each month so this is the 4th one since the repair. The pack now peaks at 237v (picture in OP is 233v) during the process. According to prolong charts, peak range should be 234-241v. Mileage has risen to 47-48mpg some of which I also attribute to slightly cooler weather.

Decided to move the multi-day conditioning treatment (with the light bulb discharger) to the winter holidays. That will be the 6th month since repair and will make it much easier to remember when to perform future reconditionings (jan/july) as they are recommended twice yearly.

 

7-reinstall HV batt
8-cycle charge/discharge batt with 120v charger/discharger to balance all modules

I have not tried other methods. Some have used hobby chargers designed for toy remote control cars to charge each module. Takes a lot of time but some buy multiple charges to speed up the process. I have no experience with those. See: Gen II Prius Individual Battery Module Replacement | PriusChat

GOOD LUCK!