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Wolf's PowIRwall
#21
My powerwall batteries with ca 7000 cells of varying SoH have been in use for nearly 1.5 years, and they've definitely been degrading (losing capacity) at different rates. Every month or two I bring the pack capacities back in balance by surgically replacing a couple of low capacity cells with higher capacity cells.
Will be very interesting to see if your packs made from carefully selected cells all degrade at the same pace, thus requiring no maintenance.
Modular PowerShelf using 3D printed packs.  60kWh and growing.
https://secondlifestorage.com/showthread.php?tid=6458
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#22
(04-13-2020, 01:47 PM)ajw22 Wrote: My powerwall batteries with ca 7000 cells of varying SoH have been in use for nearly 1.5 years, and they've definitely been degrading (losing capacity) at different rates.  Every month or two I bring the pack capacities back in balance by surgically replacing a couple of low capacity cells with higher capacity cells.
Will be very interesting to see if your packs made from carefully selected cells all degrade at the same pace, thus requiring no maintenance.
It will be very interesting indeed!
Right now it is very encouraging to see the packs come so close to each other in Ah results.
I am charging the packs to 4.2V till the "Keep" indicator comes on on the iCharger, then regen discharge at 30A to 3.0V, then storage charge to 3.7V.

I am hoping my diligence will pay off.

Wolf
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#23
I do think that the initial selection and patience will work out well. From your detailed testing and understanding of cells interactive behaviour in a pack the end result should be quite good and last longer than the typical build here.

"I'm kinda sticking my neck out as I am a huge proponent of IR and the importance of it indicating the health and longevity or a cell." +1
If you can't quantify how much they cost, it's a deal, I'll buy 5 of them for 3 lumps of rocking horse ......
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#24
Update:

#1:  Well I found another corroded cell that tested just fine had great IR, mAh and V and looked perfect from the outside.
I am now a complete believer in re-wrapping All cells.


#2: The packs are coming together very well. I have 9 totally complete 2 packs re-wrapped and 3 more waiting for their final check and re-wrapping. I had to cannibalize the 15th pack for cells that after the final test of IR and V before the re-wrap I deemed to be just a little below my stringent specifications.
The 3 packs on the right are my regen packs  and the icharger is doing a regen at 30A yea!!
Sorry the spider plant went wild. It got a trim this morning.


Now to the problem. I initially bought 20 feet of the 5p cell level fuse sheet and well ran out. I need another 15 feet to complete my packs.
I have emailed and called Battery Hookup several times  to see if they are expecting any new stock but no answer whatsoever.
I even sent Mike a PM whose signature has their advertisement for their cells for sale ( he is not an employee or part of their business) to see if they knew if any new supply would come in.
He did get in touch with them (I thank him dearly for that) and was told 3 to 4 weeks.
In the meantime I decided to take advantage of the sale of their Modem batteries and sent them an email requesting a price for 400 of the units. Got an email back saying yea we can do that for x price send us your zip code so we can give you a complete price with shipping. I did that and that is the last I ever heard from them again. Now the website says that they are out of stock. Hmm??
By the way Mike your signature is "Out of Stock" Tongue

Sorry to be so long winded but here is the question. If anyone has any 5p cell level fuse sheets available please let me know and I will purchase them.

Thanks for listening.

Wolf
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Great ABB shunt breaker seller River City Industrial
Great prices and superb service.
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#25
(04-15-2020, 12:20 PM)Wolf Wrote: Update:

#1:  Well I found another corroded cell that tested just fine had great IR, mAh and V and looked perfect from the outside.
I am now a complete believer in re-wrapping All cells.

The big question is, where did the rust come from? If it's from another cell, container, iron in water, etc. then it's probably fine. If the rust came from micro pits in the nickel layer on the cell, the oxidation could potentially keep happening and digging deeper into the casing until the structural integrity is compromised.

Maybe after 'thorough" cleaning of the cell to get as much rust off as possible, to then coat the cell where the rust was in some kind of sealant, like clear fingernail polish or lacquer. That way oxidation can't continue to develop later on down the road. Even re-wrapping may not be enough protection alone.

Just my 2 * 10^-2 Wink
Proceed with caution. Knowledge is Power! Literally! Cool 
Knowledge is Power; Absolute Knowledge is Absolutely Shocking!
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#26
(04-15-2020, 12:30 PM)Korishan Wrote: The big question is, where did the rust come from? 

Maybe after 'thorough" cleaning of the cell to get as much rust off as possible,............................
Who knows where it came from Soda, water,coffee spilled on the laptop? Battery left in the elements maybe took a bath?

Ah no that cell gets replaced with one of ~equal value  never to see the potential of getting into my PW.
I got enough cells to avoid having to use those.
It will get a rewrap though to protect ME from it shorting out, go into the discharge unit, and go away to the recycler.
Bye Bye.

The point I was making is that even though the cell looked great on the outside once the wrapper came off there was this corrosion that could not be seen before. In your automotive vernacular it's like taking the plastic bumper cover off just to find that the actual steel bumper is just about rusted out. Oh wait you live in Florida that doesn't happen to cars there just in the northeast. Tongue

Wolf
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#27
(04-13-2020, 12:40 PM)Wolf Wrote: Production has begun on the packs.
All bus bars have been completed and 9 of these packs have been built.
Every one (720) have been rechecked for IR and V and re-wrapped.

I must say I do like the Kweld a lot once you get it dialed in it gives consistent results.
Only 5 more to go and 1 spare.
Testing the Ah of the packs right now and will post results as soon as all of them have been tested.
Testing paramiters are:
Using Icharger x6 initial testing was done with a external resistor to allow 20A discharge. Once 3 packs where initially tested
those were hooked up in series to provide a charging and regenerative discharge holding tank capable of 30A either in or out.
Sneak peek at the results so far? OK



Wolf

 I am sure you noticed this. Didn't you?




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#28
(04-15-2020, 03:05 PM)100fuegos Wrote:  I am sure you noticed this. Didn't you?

LOL yes I did! Good eye.

I spotted it when I posted it and left it in there just to see if anyone would notice.
You win the prize. Big Grin
Wolf
For Info Google Drive

Great ABB shunt breaker seller River City Industrial
Great prices and superb service.
 [Image: em2566%20(1)__19172.1521541365.jpg?c=2]

Not your average Wolf       
            Cool
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#29
(04-15-2020, 12:45 PM)Wolf Wrote: The point I was making is that even though the cell looked great on the outside once the wrapper came off there was this corrosion that could not be seen before. In your automotive vernacular it's like taking the plastic bumper cover off just to find that the actual steel bumper is just about rusted out. Oh wait you live in Florida that doesn't happen to cars there just in the northeast. Tongue

LOL you'd be surprised Tongue Though, not from salt. Usually from an excess build up of mucky dirt/mud keeping it constantly in a state of wet saturation. But, does take a lot longer than those up north.
Proceed with caution. Knowledge is Power! Literally! Cool 
Knowledge is Power; Absolute Knowledge is Absolutely Shocking!
Certified 18650 Cell Reclamation Technician

Please come join in general chit-chat and randomness at Discord Chat (channels: general, 3d-printing, linux&coding, 18650, humor, ...)
(this chat is not directly affiliated with SecondLifeStorage; VALID email req'd)
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#30
(04-15-2020, 12:30 PM)Korishan Wrote:
(04-15-2020, 12:20 PM)Wolf Wrote: Update:

#1:  Well I found another corroded cell that tested just fine had great IR, mAh and V and looked perfect from the outside.
I am now a complete believer in re-wrapping All cells.

The big question is, where did the rust come from? If it's from another cell, container, iron in water, etc. then it's probably fine. If the rust came from micro pits in the nickel layer on the cell, the oxidation could potentially keep happening and digging deeper into the casing until the structural integrity is compromised.

Maybe after 'thorough" cleaning of the cell to get as much rust off as possible, to then coat the cell where the rust was in some kind of sealant, like clear fingernail polish or lacquer. That way oxidation can't continue to develop later on down the road. Even re-wrapping may not be enough protection alone.

Just my 2 * 10^-2  Wink

If I'm hijacking this thread, feel free to orphan this post. Since you bring up rust, there's something I've always been wondering - If electrolyte is so caustic, why don't all cells rust from the inside out within a matter of time? is the nickel plate really thick on the inside of the cell?
Check out my long-term capacity test of 18650s: https://secondlifestorage.com/showthread.php?tid=6868
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