Begginers Guide to Processing 18650 Cells | Cell Database


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Quick question regarding batteries.....
#1
Hi guys. Have a quick question. Which would you recommend, 18650's or the Johnson Controls batteries Jehu Garcia has available? (12s2p)

What I am wanting to do is build a "power wall" battery bank. I have a large solar power array I have been building for the last 5 years.... and need to  get this thing done. I have almost everything already including 2 - Schneider  60/150 Mppt charge controllers, 4860 inverter, 5kw+ of solar panels....

I know 12s is not ideal for a 48v system.... so I figured if I got the 12s ones I would probably end up tearing them apart to make 14s packs. Or would I be better of geting the 5s ones and going with 15s???? What would you do?
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#2
14s. 12s is way to low and 15s might be to high if you want to be able to use all capacity some day
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Current: 10kW Mpp Hybrid | 4kW PIP4048 | 2x PCM60x | 83kWh LiFePo4 | 10kWh 14s 18650 |  66*260W Poly
Upcomming: 14S 18650~30kWh | Automatic trip breakers, and alot more
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#3
Check the voltage range your inverter can manage, 12s can be too low, and with 15s even setting the maximun voltage of inverter can be underutilizing the cells.
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#4
My inverter is a XW 6048. The specs says it will work with 40v to 64v dc.
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#5
12S isn't really a thing for a 48V system. If your inverter works from 40V to 64V then that clearly hints at 14S/48V lithium, 42~58.8V. Or 16S in case you want to go LiFe.
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#6
(09-07-2017, 07:46 PM)shanejackson Wrote: My inverter is a XW 6048. The specs says it will work with 40v to 64v dc.

40/12 = 3.3333  So your packs won't go under 3.33V, it isn't a bad idea don't let the cells go under 3.3 to gain cycles,  so it will work just it is your choice and ensure you can set the maximun voltage maybe 4.1*12= 49.2 you don't want to charge your cells to 5V.
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#7
3.33V under load wont work. If you have slightest drop that will kill the system before you even used 50% of the capacity on the cells. yes you gain some cycles but when do we need the power? When the sun isnt out.. And it would SUCK if you cannot use the last 50% 3 times a year when we need.

Its always very bad practice to let the limits of the inverter set cut off... Only on the high side if so and never on low side.

Example: 40V on the inverter. Lets say you have max load or a spike. You might end up at 42V at the cells. Then you have internal resistance due to the high load. That is another 0.2-0.3V per cell. Lets say 0.3V. So the cell resting voltage would be 42+12*0.3) = 45,6/12= 3.8V resting!!!

Thats not much you can use... Imagine first spike when the washer turns on and your inverter shuts of due to low voltage Tongue
Follow me! >> YouTube / Forum system setup / My webpage  Diy Tech & Repairs

Current: 10kW Mpp Hybrid | 4kW PIP4048 | 2x PCM60x | 83kWh LiFePo4 | 10kWh 14s 18650 |  66*260W Poly
Upcomming: 14S 18650~30kWh | Automatic trip breakers, and alot more
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#8
Yeah exactly, you can't calculate a system with the ultimate minimum of the inverter as a baseline. 40V will be the point of undervoltage shutdown, long before that you will have undervoltage warnings. And constant shutdowns on spikes. This will be super annoying to run.
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