P0A80 Code

Never heard of anyone using a transformer? The standard way to do a load test is with a ~50w 12v bulb on each module... If you have standard halogen headlight and not LED you can use one of those... Or most department stores sell low voltage lights that fit that spec. You measure the voltage loss of a module after being hooked up to the bulb for two minutes. Build a spreadsheet of your results. There's lots of additional steps and things to inspect, but that will get you started.

 

Welcome to PC! I would not advise using a transformer to try to load a DC voltage source. DC will see that as a dead short. That could be kind of exciting, but it won't do the cell any good.

Myself, I would not be interested in messing with individual modules since they are all the same age and it just becomes a whack-a-mole game. That's fine if you have lots of time for that stuff and don't mind getting stranded now and then. I recommend a new battery or, if that's too dear, an intact near-new used one.

If you chose to go the whack-a-mole route, there are lots and lots of threads here about testing and replacing cells. But it's also possibly an issue with the wiring harness. Check for corrosion before getting too carried away. Those little tiny wires and terminals are very vulnerable to corrosion. And make sure you use an inch-pound torques wrench to tighten the nuts. I don't remember the torque value, but it is not very high.

 

That's not fair... There's plenty of people who replace a bad module and get the car back on the road for a year or two without any issues. Your dismissivness is based on the fact you could afford to drop $2K to fix it, not based on your experience with actually fixing them. Most people can't afford to spend that much money for a brand new pack, but they can spend a few hundred dollars to buy themselves some time and you can often go several years with only replacing a couple modules, which isn't wack-mole, it's called not unnecessarily wasting thousands of dollars.

 

No way would I do that with my wife's car. I wasn't about to just hope for a couple years of reliability. She drives a LOT. If it was my own car and just a go-to-work beater, maybe. And I didn't spend even close to $2000 even before Toyota dropped their prices. Nor did I buy a new battery. A two-year old battery is almost as good as new and costs a whole lot less. But this forum is full of bad experiences with rebuilders. Not that it can't be done well, but it's rare to find someone who has the skill, tools, and patience. I have a hard time advising someone to take that risk. I'll mention it, but I won't advise it.

 

You need to do what you need to do. And what you can afford.
Spending a few hundred dollars to keep the car going for a year or two so you can save up enough
money to get a new part.
It's always best to get the best part. Sometimes, you get the best you can afford.

In a year, or two, perhaps the price for a battery will come down. Who knows?