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.

 

Don’t charge the battery as a cell. Charge them in place when assembled and you’ll have far fewer issues. There are tons of YouTube videos on this.

 

did the same charged without clamping on the first 11 modules.

i am only a few milimeters away from getting them back in. I cant see any visual difference between the modules i didnt touch and the ones that swelled ( the swelling came back a good bit to the point where i cant see a difference between a good and bad one.

Perhaps i am asking for trouble but I am tempted to freeze them to get them to fit. If i get those last few milimeters back while they are cold and get the clamp on perhaps they wont explode when they get to room temp again.

Or perhaps they will and i will have battery acid all over my kitchen table and potentially me.

anyway i guess i'm posting this to talk myself out of the idea.

Any thoughts? Really scrap all 11?

 

There is no acid in the modules.
NiMH uses alkali for chemical reactions.
When you assemble the modules into the case and tighten them with two guides, check that they all touch each other and do not stick out. They may still serve. In any case, you have learned a lesson in how to charge modules for a hybrid battery.

 

much thanks mithrandir. Freezing didnt make much difference. I clamped the 11 mistreated modules together and am now using an led driver to cycle them while clamped at a current i can control. I also have a fan blowing to keep temperature down. I ordered a hobby charger to do this properly in future.

hoping that when they come out of the clamp they might fit back in the harness for the prius but if not i should still have some usable cells for a solar project or some other use.

In the meantime i picked up an old pack from a scrapyard here in Dublin. 400 euro. I can pull more modules from that as needed.
Absolute shame the fine cars they were tearing apart there nothing wrong with them. The guys in the yard told me the taxi drivers (nearly all prius drivers) get some grant to buy a new car so long as they produce an end of life cert for their old car. So as soon as a headlight gets smashed they scrap the whole thing. He had to turn away a taxi driver when i was there cos his yard was full. Irish government for you. I will have to rain vengenace upon them by getting battery modules and old car parts and becoming as wealthy as conor mcgregor and run for president myself.