Building My First Pack

1xAA

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Sep 27, 2020
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I have acquired around 425 x 1865s that I plan to use for off-grid storage. I expect to get around 400 good ranging from 1700-2700mah after testing, which should be complete in another week or two. Hoping to get some opinions/suggestions on the best way to utilize these with my inverter and sorting them into packs based on capacity. The inverter is a 12v 1000w pure sine, BUT I would certainly consider a 24v inverter in the future given the voltage range of the 6s scenarios, but for now I am confined to a 12v setup. The trays I bought to hold the cells are 4x5, which is kinda throwing me off a bit as far making a few 3s packs-maybe I could just cut off or leave one row empty?



Thanks for any help/suggestions.
 

Korishan

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Trying to make 12V out of Li-Ion is very difficult. Try to go 4s if possible if the inverter/charger can handle the slightly higher top voltage.

For the holders, you could get some singles and then just clip them on to get a better arrangement.
However, for such a small setup, I would suggest using the holders to make all parallel packs, and then serial connect the packs. Don't try to make the 4x5 a 4s5p configuration.

If you insist on 3s, or the inverter/charger can't handle the top voltage limits, then just use the singles to make them fit. Make it 4x6 holders, which will be 3s8p (2 rows of 4 connected in parallel). Or you could get some of the 2 cell holders and go 5x6, which would be 3s10p (again, 2 rows parallel, but 5 in each row this time)
 

1xAA

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Renogy inverter spec sheet states over voltage shutdown is 15.5v. Data sheet also states low-voltage alarm is 11.0v but really activates at 12.1v based on what I am observing. Hard to put any load on this thing w/o it shutting down too early. I really need to find better products. Make do for now, I suppose.

Doesn't look like this inverter is a fit for 4S. Undercharging to 3.8 would defeat the purpose with this inverter it seems.
 

OffGridInTheCity

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Been down this road myself... suggest you scrap the12v plans for Lithium-ion. Neither 3s or 4s will work more than 50% due to incompatiblevoltage/DODranges- very unsatisfactory all around! The bright spot with 18650/lithium-ion is that you can go 7s / 24v or even 14s / 48v and it works perfectly with most equipment.

if you insist on 12v, thensuggest LifePo4 cells and do 4s - this is very compatible with 12v 'stuff'.
Some LifePo4 cell examples....
-https://batteryhookup.com/products/20-k2-26650-lfp26650ev-3200mah-lifepo4-batteries-new
-https://www.batteryclearinghouse.com/products/lot-of-144-cells-used-a123-anr26659m1b-lifep04-3-3v-2500mah-in-3-emc-packs
and of course there are brick/pouch LifePo4 as well :)
 

1xAA

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OffGridInTheCity said:
Been down this road myself... suggest you scrap the12v plans for Lithium-ion. Neither 3s or 4s will work more than 50% due to incompatiblevoltage/DODranges- very unsatisfactory all around! The bright spot with 18650/lithium-ion is that you can go 7s / 24v or even 14s / 48v and it works perfectly with most equipment.

if you insist on 12v, thensuggest LifePo4 cells and do 4s - this is very compatible with 12v 'stuff'.
Some LifePo4 cell examples....
-https://batteryhookup.com/products/20-k2-26650-lfp26650ev-3200mah-lifepo4-batteries-new
-https://www.batteryclearinghouse.com/products/lot-of-144-cells-used-a123-anr26659m1b-lifep04-3-3v-2500mah-in-3-emc-packs
and of course there are brick/pouch LifePo4 as well :)


Did you mean 6s (25.2) or 7s (29.2) for 24v inverter? I was more thinking at least 2 separate 12v packs with these cells so I could go series and a 24v inverter in near future. I ordered a few 6s BMS boards to play around with.

EDIT: NVM I see Over Voltage is around 30v for 24v inverters.
 

1xAA

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done...in the end I am not sure this is the way to go as some suggested. Oh well, decent first pack. Did 12v (3s) pack. Just didn't think I had enough cells for a decent 24v pack. Pack has a low watt assignment.
 

1xAA

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Anyone know what size shrink wrap I should get for a 9"x3" (20" long) pack?
Gotta fig out a better way to charge this than a 5amp hobby charger.
 

jonyjoe505

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Gotta fig out a better way to charge this than a 5amp hobby charger.
depending on what your power source is, if AC you can use a laptop charger (19 volts) and run it through it a buck converter (set to 12.6 volts). If charging from a 12 volt dc source, you would need a boost/buck converter, the boost converter will boost the 12 volts to 18 volts, then the buck converter will reduce it to 12.6 volts and maintain the max amps you need.

This is a picture of a boost/buck converter 12.6 volt charger, I charge at 6 amps but it can do a max 10 amps. Its cc/cv and gives my 3s li-ion pack a good charge, I prefer this charger over my 15 amp ISDT hobby charger. This one has a LED volt/amp meter so I can see battery voltage/amps in realtime as its charging. Also it has an 80mm cooling fan, the converter gets hot at the higher amp settings.
1 boost buck internals.jpeg
 

daromer

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You get same capacity with going 7s as going 3s with same amount of cells. As long as you can split them evenly.
 
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