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14s50P capacity variances
#11
(06-07-2020, 02:14 PM)ajw22 Wrote:
(06-07-2020, 01:00 PM)ShortcutShawn Wrote: Wow, so you use all cells untested ?

(06-07-2020, 11:28 AM)ajw22 Wrote: Capacity testing, sorting, building packs according to Repackr takes way too much time.

Badly worded.  I still test for capacity, but just to make sure it has at least ~75% of the original capacity.  Then I put them in a dated box and store them for 2 weeks ~ 3 months, depending on my schedule.
I then take cells from the oldest box, check voltages to make sure they've not self discharged, then put them straight into my 14 new packs in a round robin fashion (like a card dealer).  That tends to mostly spread cells from one source over all 14 packs.
With avg 2000mAh, 100 cells/pack, the capacities end up remarkably close at the end.  I don't keep statistics, but I'd say 10 packs don't need any adjusting, the other 4 need maybe +/- 3000mAh adjustments.

Also, the cells degrade at varying rates, unless you have fairly new perfectly matched cells from the same manufacturer.  What's the point of spending so much time on getting it perfect, when it's going to go out of balance after a few months~year of use anyway.
Yes sir - @ajw22's approach is similar to what I use / similar philosophy.   My oldest packs are 2 years with 652 charge/discharge cycles.  They're #15 - #42 below and still don't need balancing / appear to be perfectly healthy Smile
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#12
I dont test ir. I dont use repackr. I use a bucket variance and sort it accordingly. My walls have almost 5 years without an issue. You dont have to test ir if you test with a proper current since that itself test the ir.

With that said lower current per cell afterwards including larger packs do alot.
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#13
As I said I may be p-u p-ued with my technique and that’s OK.
I do agree it is a bit more labor intensive and probably not as necessary for some.
ajw2 3d printed cell holders are ingenious and easy to replace a bad cell or add a higher mAh cell.
Perfect design for maintenance
Offgridinthe city builds extra space into the pack to add cells if necessary to balance the packs
Daromer has his packs running almost 5 years without a hitch.
 
Everyone has their way of building the packs they want and so do I.
 
In my case by using the cell level fuse sheets and my buss bar design it would be very difficult to add subtract or change a cell in my packs.
So I opted to be very picky with the cells that made it into my packs. I wanted to have a relatively maintenance free battery for as long as possible.
Balanced from the get go and stay that way for quite a while.
If daromers pays little mind to IR as long as the cells have a good mAh result at a 1A CDC then it will be randomly chosen to go into his packs.
Perfect!
Just means that if I take a couple more miniscule steps my packs should run maintenance free for at least 5 years if not 10. I’m good with that.
Although I’m not sure what I’m going to do with my spare time. Oh Yea build another pack.
 
So as far as I am concerned all the advice given is good advice with the “proven” methods of building a successful power wall with 18650 or at least cylindrical cells.
 
In the final analysis the choice is yours.
Best of luck with your build.
 
I personally  would put the packs together and see how it all plays out. You may need to do a little fine tuning here or there.
But it would be a great learning experience to see how your packs work.
 
Wolf
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#14
(06-08-2020, 11:42 AM)Wolf Wrote: As I said I may be p-u p-ued with my technique and that’s OK.
I do agree it is a bit more labor intensive and probably not as necessary for some.
ajw2 3d printed cell holders are ingenious and easy to replace a bad cell or add a higher mAh cell.
Perfect design for maintenance
Offgridinthe city builds extra space into the pack to add cells if necessary to balance the packs
Daromer has his packs running almost 5 years without a hitch.
 
Everyone has their way of building the packs they want and so do I.
 
In my case by using the cell level fuse sheets and my buss bar design it would be very difficult to add subtract or change a cell in my packs.
So I opted to be very picky with the cells that made it into my packs. I wanted to have a relatively maintenance free battery for as long as possible.
Balanced from the get go and stay that way for quite a while.
If daromers pays little mind to IR as long as the cells have a good mAh result at a 1A CDC then it will be randomly chosen to go into his packs.
Perfect!
Just means that if I take a couple more miniscule steps my packs should run maintenance free for at least 5 years if not 10. I’m good with that.
Although I’m not sure what I’m going to do with my spare time. Oh Yea build another pack.
 
So as far as I am concerned all the advice given is good advice with the “proven” methods of building a successful power wall with 18650 or at least cylindrical cells.
 
In the final analysis the choice is yours.
Best of luck with your build.
 
I personally  would put the packs together and see how it all plays out. You may need to do a little fine tuning here or there.
But it would be a great learning experience to see how your packs work.
 
Wolf
Personally - my hat's off to you!   What's not really very clear is the 'life span' of these packs/batteries.    It may indeed turn out that your methods extend lifespan = less maintenance/replacement over time.    For me, I'm just too lazy to take the extra steps you do - but doesn't mean I don't admire your work Smile

>Oh Yea build another pack.
Finished my 6th (14s100p) battery a few weeks ago and tidy'ed up my remaining 700misc cells...   but then, late night, just ordered hundreds of RingBatteries for the 7th one.  It was the 0.50c / cell + the apparent COVID 'run' on cells supplies that did me in - I must get more cells before they are all gone!   Please help me stop!! Dodgy
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#15
(06-08-2020, 02:25 PM)OffGridInTheCity Wrote: >Oh Yea build another pack.
Finished my 6th (14s100p) battery...............................................t COVID 'run' on cells supplies that did me in - I must get more cells before they are all gone!   Please help me stop!! Dodgy

This warning should help you stop!
Right, in a pigs eye. Or when pigs fly..........



Now Offgid be a good boy and listen to the goverment and the lawers. (There is a pink floid song about that. At least trusting the government.)

Don't play with things that have warnings on them.
If that was the case none of us would have done anything like we have.

Another good case for re-wraping cells

Wolf
OffGridInTheCity likes this post
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Great ABB shunt breaker seller River City Industrial
Great prices and superb service.
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            Cool
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#16
(06-08-2020, 11:42 AM)Wolf Wrote: In the final analysis the choice is yours.
Best of luck with your build.
 
I personally  would put the packs together and see how it all plays out. You may need to do a little fine tuning here or there.
But it would be a great learning experience to see how your packs work.
 
Wolf

Believe me, there are a quite large number of newbies learning from your styles, experienecs and tips.
Thanks for your lessons and guidance, specially answers noob Qs and some repeated questions cuase some of us are lazzy enough to search properly 

Thanks again!
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#17
507Powerwall +1

I have learned a lot from Wolf and appreciate all his advice and help. He is the reason I bought a good IR tester.
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