The grim reaper has finally arrived

After asking others more knowledgeable than me about OBD2 readers it appears that my original blame on corrosion was not accurate because too many systems are giving bad data and problem is with a bad OBD2 reader. However, the corrosion needs to be addressed as well, so OP's concern with addressing that is valid.

 

A little corrosion on the bussbars and nuts does not need to be addressed. If there is corrosion on the voltage sensing wires orange connector that plugs into the battery ECU, then that does need to be addressed, but I do not think that is the case based on the screenshot in post #13. What needs to be addressed in the OP's situation is the bad module in block #6.

 

I wouldn't trust those modules... What's more you only have one bad module not two and a common mistake people make is replacing both modules in a block when only one module is bad. This is a problem if your replacement module doesn't match your existing modules in age and capacity and if you replace both of those modules in the same block you're doubling down on the level of hassle you might create for yourself.

In my opinion professor Joe sells the highest quality replacement module because he's spent tens of thousands on lab grade testing gear several times over the past couple decades: Oregon's Trusted Hybrid Battery Supplier: 2nd Life Story

 

It might not hurt but its the source of corrosion that eventually ends up in the ECU and buying a new wiring harness with the link in my signature, will last way longer than just cleaning the corrosion in the ECU.

 

Usually there's only one bad module in a block and when you replace that module with one that doesn't match the modules in the pack you have a problem like the one you're having. And if you replace both modules in a block you double the likelihood of having a problem. So only replace the module that has tested as bad.

As for getting all modules to have the same voltage and near same capacity that's called balancing and you can do that with a high voltage trickle charger sold by Maxx Volts or HybridAutomotive... OR build your own, or buy a variable DC power supply online that has at least 250v at 1/3 of an amp. All the information on the HybridAutomotive websited will teach how to do it.

Another method, which is less effective for this battery type is to connect all the battery terminals together in parallel, as in connect all the positives together on one wire and all the negative together on another wire and hook up a multitester and should read 7 something volts and that votage will equalize to all modules after a while, but the modules capacity might be a bit off compared to the other method.

 

@2005prius, This idea, called equalization, is not less effective, it is totally ineffective. Don't waste your time on this.

Equalization is not the same as balancing. If you want the modules to be at the same voltage as the others, use a RC charger to charge it up to the voltage of the others. However, you should still balance the battery pack by grid charging after it assembled.

Instead, focus on the first two paragraphs in PriusCamper's post.