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lifepo winston
#1
Hai Ya All...

My regular supplier had to quit due to some new rules from our roberment....

Im looking for quite a while to the lifepo4 cells for my powerwall.
They are somewhat expensive...
Is it possible to buy every month 1 cell to 2 cells of 400ah and that every month.
So i obtain in one year, one and a half the required 16 cells for one string.
Or is this time to long and it is better to buy them at one go?

More doubts on this from my side: 
I can give every cell when it is coming in, his first charge and than maintain every 3 to 6 months.
But the first cell in will have some more cycles than the latest that was coming in.
Or only charge them back up if there was a drop, or have they an ideal storage voltige?
Or wait with their initial charge till i gather all 16?

https://www.ev-power.eu/Winston-40Ah-200...html?cur=1

Enough with my rambling: if it makes any sense?
Any thought is very appreciated. Thanks in advance.
Selling everything at marketplace.
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#2
(10-22-2019, 06:41 PM)100kwh-hunter Wrote: Hai Ya All...

My regular supplier had to quit due to some new rules from our roberment....

Im looking for quite a while to the lifepo4 cells for my powerwall.
They are somewhat expensive...
Is it possible to buy every month 1 cell to 2 cells of 400ah and that every month.
So i obtain in one year, one and a half the required 16 cells for one string.
Or is this time to long and it is better to buy them at one go?

More doubts on this from my side: 
I can give every cell when it is coming in, his first charge and than maintain every 3 to 6 months.
But the first cell in will have some more cycles than the latest that was coming in.
Or only charge them back up if there was a drop, or have they an ideal storage voltige?
Or wait with their initial charge till i gather all 16?

https://www.ev-power.eu/Winston-40Ah-200...html?cur=1

Enough with my rambling: if it makes any sense?
Any thought is very appreciated. Thanks in advance.

The reason I keep coming back to 18650 is that they are individually smaller units and I can mix and match different purchases and vendors over time.    Maybe buy 100ah or 50ah instead of 400ah?  and then the same idea would apply somewhat - i.e. you could mix and match thru the coming years.
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#3
Hmmmm, nice thought.
Just treat them as 18650 parallel packs.
Buy every half a year 16 50ah or so and connect them parallel to the exiting cells?
Would save a tremendous amount on costs for the bms.
Somehow i don't think this will be good to parallel different 50ah units over the length of time.
Probably for the first 3 or 4 times? and then start a new parallel pack?
3 x 50ah parallel makes 150ah, on one bms?
Selling everything at marketplace.
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#4
(10-23-2019, 04:58 PM)100kwh-hunter Wrote: Hmmmm, nice thought.
Just treat them as 18650 parallel packs.
Buy every half a year 16 50ah or so and connect them parallel to the exiting cells?
Would save a tremendous amount on costs for the bms.
Somehow i don't think this will be good to parallel different 50ah units over the length of time.
Probably for the first 3 or 4 times? and then start a new parallel pack?
3 x 50ah parallel makes 150ah, on one bms?

What I'm thinking is....   say you buy 8 x 50ah (instead of 1 big 400ah).   So 16 * 400ah would be 16 * 8 = 128 50ah(s).    That's 8 in parallel * 16.    If one purchase get's you 40ah (instead of 50ah) and some are 45ah instead of 50ah etc...  you can mix/match/distribute to even things up - as that would be 8 units per 'pack' and give you some statistical options .      If a few of these 'go bad', you can replace them more easily.

If you did 16s8p (of 50ah), you would still only need to BMS 1 battery same as if you did 16s1p (of 400ah).    Maybe 100 instead of 50 or even a mixture - the point is, a lot more flexibility in purchases?        Of course you have to hook them all together etc - so hookup is a bit more complicated.

I agree, its easy to arm-chair quarterback here... so you know, just idle thoughts....
100kwh-hunter and Solardad like this post
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#5
I bought from two separate vendors so my "48V" LiFePo4 packs are:
2 packs each made with 4x 30AHr in parallel x 16, so 120Ahr@48V each
2 packs each made with 2x 60AHr in parallel x 16, also 120Ahr@48V each
total of the 4 packs =~480Ahr
2nd vendor's product had much better construction but they both seem to be working fine so far
100kwh-hunter likes this post
Running off solar, DIY & electronics fan :-)
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