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why 80p for powerwall?
#21
Ahh that is No go. You should never have different Numbers or types in series unless you have deep testing done. Never Ever.

Parallel is ok but series isnt. It may work but IF you add Up that the cells allready from start can vary Up to 30% in current the cell count can get it Up to or above 50% variance per cell.

Same cell count. Same amount low as high capacity per pack internally random is best way doing it unless you plan to do it calculations with 4wire and you know the age. Smile
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#22
(01-23-2020, 11:54 PM)mike Wrote: No, not at all. This is exactly what I'm doing and it works GREAT. I even wrapped mine with heat shrink and the compression of the shrink creates a rock solid pack.

There's some info in this video...


What's the dimensions of each cell pack and then how wide are all 14 laid out like that??
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#23
(01-24-2020, 09:08 AM)daromer Wrote: Ahh that is No go. You should never have different Numbers or types in series unless you have deep testing done. Never Ever.

Parallel is ok but series isnt. It may work but IF you add Up that the cells allready from start can vary Up to 30% in current the cell count can get it Up to or above 50% variance per cell.

Same cell count. Same amount low as high capacity per pack internally random is best way doing it unless you plan to do it calculations with 4wire and you know the age. Smile
Note: All of my base packs were built to have (as close as i can) 130ah. I didn't worry about cell count, but focused on getting 130ah at 500ma discharge capacity.

My first battery is made up of 7s ICR18650 MF1 (2150mah) packs in series with 7s Samsung ICR18650-22P-M (2200mah) and after 528 cycles its doing well with no balance problems.   I agree these packs were pretty well matched - effectively the same 62cells per base pack, 124 per pack.  

My second battery is a parallel mix of base packs.  Each pack has 1 base pack of grey LGABB41865  (2600mah) in parallel with 1 base pack of Panasonic NCR18650A.   This one has 350cycles. This is more to @Daromer's advice - e.g. parallel is OK.  


I did have an experience where I had 5 (of 14) packs made up of Green Sony US18650CR-G5 and G7(s) in series with the LGABB4185+NCR18650As and those 5 just would not balance/behave compared to the others.  I'm talking 150mv differences no matter what I did.  AND the packs has same 130+130 = 260ah.   However, I put it down to IR and Chemistry rather than mix/match serialization. Maybe serialization compounded the Green Sony IR/chemistry mismatch. I set-aside those Green Sony cells because IR was over 200 compared to 100'ish on *all* the other cells.
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#24
Once again the best method is to have same amount and mix 100% in each string. You may be Lucky and it works or you have to go back to the bench and redo. I dont like redoing Smile
My packs Still just run and they are totally random but är by My Main criterias


Smile
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Current: 10kW Mpp Hybrid | 4kW PIP4048 | 2x PCM60x | 100kWh LiFePo4 | 20kWh 14s 18650 |  66*260W Poly | ABB S3 and S5 Trip breakers
Upcoming: 14S 18650~30kWh
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#25
I design mine at 60p only because I find that's the right speed for me in my spare time to build them without taking too much time. But then when I install it I put it in parallel with each other with 12ga wire. Currently they're stacked 6 high so it's an effective 360p. This allows me to slowly build my packs (I don't have mike's stamina on building 300p packs!). I find stacking them instead of the wall method allows you to have the most effective area. The wall method requires more wall space.

 

These packs stay within 30mV or better with each other. I make sure there are no self discharges by charging each cell up to full and have them sit for a minimum of 2 weeks. I find 1 week is too short and at about 2 weeks is where I really notice them. All it takes is just one cell to slowly drag down the rest of the pack. My packs are made out of two different batteries only, about 60% panasonics and 40% samsungs. This keeps the battery characteristics quite similar.
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#26
I still cant decide whether to go 80 or 100 either. For me, I'm thinking more about the structure of the plastic holders than the capacity of the battery. 80 works really well but 100 starts to get a bit heavy and bendy.
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#27
You basically get same length with 100p as 80p if you stand the holders up. The problem there is that you get 5 cells in height instead of 4 and therfore cannot have the same easy layout of busbars. In that case 160p can be good as well to start with.
NOTE! My links supplied in this message may be affiliated with Ebay and by clicking on them you agree on the terms.
YouTube / Forum system setup / My webpage  Diy Tech & Repairs

Current: 10kW Mpp Hybrid | 4kW PIP4048 | 2x PCM60x | 100kWh LiFePo4 | 20kWh 14s 18650 |  66*260W Poly | ABB S3 and S5 Trip breakers
Upcoming: 14S 18650~30kWh
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#28
160p!? Wow... I'm gonna need more cells ;-)
Follow my Powerwall journey here: 
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Building the following:
20kWh Powerwall
8kW Solar
30kW Heating system
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#29
Mike has 300p, or is it 400p(?) I don't recall Wink
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#30
(01-27-2020, 06:54 AM)The Kilowatt Challenge Wrote: I still cant decide whether to go 80 or 100 either. For me, I'm thinking more about the structure of the plastic holders than the capacity of the battery. 80 works really well but 100 starts to get a bit heavy and bendy.

This brings up a good question... how often does one have to pull cell packs/modules for maintenance on harvested cells?
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