Replacing one specific cell everytime

But how old is the whole shebang this is the original battery and you've replaced this particular set of modules once or twice or twice something like that? And I'm assuming you've cleaned all the bus bars and the studs that the bus bars eventually go into the nuts etc? I have to ask so then it just could be because everything is out of balance You keep replacing this one or two modules and leaving the rest. So now maybe if you had a capable charger and discharger you could charge and discharge the system twice maybe three times and see what that does for you might help you immensely these are decisions you have to make with data and then figuring the amount of time if your time is pretty much free or you're doing this when you're goofing off or what have you then good on you so you're essentially doing this labor free which is always nice if you can make that happen. You may need to just get everything balanced.

 

Two explanations:

1) There's two plastic-metal modules per block and 6 cells in each module. If you have one bad cell and replace both modules with used ones that don't match your existing pack well you're doubling the likelihood of getting warning light. Only replace one module per block. Move existing modules around if you have to so you avoid replacing both in the same block.

2) The person you're buying modules from is selling you junk modules because they lack expensive testing equipment. Professor Joe has spent more than $20K on testing equipment 3 different times in last dozen+ years and he also teaches hybrid repair at his local college. He'll always sell you a reliable module: https://2ndlifebattery.com/contact-us/

 

The person you're buying modules from is selling you junk modules because they lack expensive testing equipment. Professor Joe has spent more than $20K on testing equipment 3 different times in last dozen+ years and he also teaches hybrid repair at his local college. He'll always sell you a reliable module: https://2ndlifebattery.com/contact-us/

PC, you focus too much on expensive testing equipment.
It's more about the knowledge of the "tester" than the cost of the equipment.

Someone can buy the most expensive equipment in the world, but if they don't know anything about basic electricity or batteries, they'll still likely screw it up.
Someone who knows what they're doing can tell if a module is good or bad with even the cheapest equipment.

Go buy a 24 seer $15k heat pump system and have Jimbo the self-proclaimed handyman from down the street install it in your house.
Now buy a 14 seer $3k Goodman heat pump system and have it professionally installed by a competent, quality HVAC company.
I'd be willing to bet the $3k system will work better. The name on the service truck is more important than the brand of the equipment.

 

I agree with this... But knowing a bad module in the moment is entirely different and way easier than re-building a pack with the maximum available 3 year warranty that is still functioning normally when that warranty expires. That requires expensive equipment and a really nice library of good, great and greatest modules. And to your point, it also requires years and years of experience by a technician who is always trying to improve and refine their methods.

 

An inexpensive hobby charger will give a very good opinion if a module is good or bad.

All that is needed to be done is run a module three times through a discharge / charge cycle. That is one of the built in modes of the hobby charger. There's a few limits that need to be setup first, then start up the 3x cycle.

Then record the numbers coming out in terms of mAh discharged from the module during each of the three times. If the numbers are under say below about 2000 ma per discharge cycle it can be considered bad. On the other hand if the module is discharging 3000 mah or higher it's probably good. However it really depends on the condition of the rest of the modules in the whole battery pack. Each module you put back into the pack needs to be in the same ballpark in terms of discharge capacity. So for example 24 modules test around 3500 mah discharge capacity and 4 remaining modules are all around 1200 mah capacity, then replace those 4 worst modules with other used modules.

Therefore, all 28 modules in a pack should all be tested in this way using a hobby charger and then sorted from worst to best. Then look at the numbers and pick a capacity cutoff value where you end up replacing modules with other used modules. Of course, those used modules being put into the pack also need to be capacity tested in the same way, and verified to be at least as good or better then the rest of the modules in the whole pack.