Prius battery NiMh cells puff up a bit during charging - how to stop it...

Following these recommendations also allows for the checking of self discharge, which usually is an important part of how well a pack will perform in the car. ie voltage diff between end of charge and after 24 to 48 hours or more after end of charge cycle,

Edit: and checking the voltage in no way means having to leave the modules clamped ( longer than what's recommended ) to take the voltage readings, in case that is confusing....

 

If all the modules are dropping that fast, then they are effectively depleted. Unless you're able to charge them, your car won't be able to start. The HV battery supplies power to the transaxle to act like a large starter motor, so a dead/depleted HV battery = no engine spin = no way to start.

 

The entire idea of reconditioning modules, especially weak modules is to try to get some more life out of them.

Putting the 4 replacement modules in the pack randomly might help, might get the car to start, might give a little bit longer run time for the Prius, or it might not !! There are a lot of IF s' that are in play if you choose to try that solution.

If you haven't already I'd suggest you put one or all 4 replacement modules through one cycle to see how they perform, So you know a bit more about them and can see them in the (DrPrius app for android phones) which I hope you'll get and use to monitor your Prius pack while its in your car.
DrPrius page Hybrid battery diagnostic and repair tool for Toyota and Lexus
If you have iPhone the app to use would be Hybrid Assistant. Hybrid Assistant work with both iPhone and Android.
Hybrid Assistant page Hybrid Assistant

All you'd need to buy would be an ( Elm 327 ODB2 adapter ) sold at both Amazon and Ebay / with recommendations of adapter tested by the app authors at there web pages

DrPrius adapter recommendations Hybrid battery diagnostic and repair tool for Toyota and Lexus

adapter recommendations Hybrid Assistant: OBD

 

Battery Reconditioning is a fairly hard subject to both teach and learn.
Unfortunately, there is no easy way around all the different possibilities any one teacher / learner can get exposed too, and there are way more exceptions to the ( generally excepted rules ) than meets the eye, which makes learning really hard and teaching a pain in a lot of cases.

edit: the impedance module ? ( the first I've heard of it ) is a measure of the cells internal resistance and can be a good indicator of the viability of the cells in a module.
I'd be interested in knowing if the impedance module is a piece of hardware or if it's an add-in to the chargers software

 

I ran a discharge/charge cycle with 4 modules outside the clamping mechanism and they are all swollen. It's been 3 days. Can I use the clamp method to bring the swelling down?

 

They are scrap.