Prolong charger on cells out of the pack

Get the biggest house fan you can find and yes in theory you can wire up Prolong direct to a pack bolted into a rack, but without the covers and orange plug you're eliminating all the safety systems, so consider how to address that so if you or a loved one accidentally bumps into something no one gets fried...

As for evaluating the modules... Build a spread sheet of voltage before charging, then run them for 24 hours on prolong then get voltage and load test data 3 or more days after full charge and balance. Once you find the best modules do reconditioning and see if they hold up. If you can get a thermal camera to view them when they're charging you'll likely find cells that are running hot even though they test healthy. Gotta get rid of those ones.

 

Get in touch with Professor Joe at: https://2ndlifebattery.com/contact-us/

He's got a partner who's based in the islands and those battery refurbishing folks usually have big piles of what you need.

 

If you have spare cells outside of your Prius, I’d advise getting a hobby charger to charge them instead of the prolong. These are very cheap, and can automatically do several charge /discharge cycles to estimate the capacity of the cells. The fancier ones even have multiple channels so you can test several cells at once. Then you can create a spreadsheet and pick the best cells to put back into your car. Just make sure you clamp the cells before charging, as they have a tendency to swell if charged outside of the pack.