Trying to wrap my head around this

[Wellfooled]

I was looking at Fortune 100Ah cell at https://www.electriccarpartscompany.com/Fortune-100Ah-Aluminum-Encased-Battery and thinking I could purchase 8 of these and wire them up 2P4S and get 800Ah of power from them. Then I looked more closely at LiFePo Wiring Configurations.PDF and I'm not sure I understand. On the 2P4S page it shows Ah=2X Cell Ah (assuming balanced cells) which I take to mean in my case Ah=2X 100Ah or 200Ah for the entire pack? Is that correct, or do I misunderstand? Like just about everything else? In other words, if I purchase eight (8) 100Ah cells and configure them in a 2P4S fashion, how many Ah's do I end up with? And yes, this makes my brain hurt. And I assume that configuring them in a 4S2P with two BMS's doesn't change anything relative to Ah's, correct?

And as always, I appreciate more than you know the time you take to answer a noob's questions.

 

[rmaddy]

If you have 8 3.2V 100Ah cells and you put them in 2P4S then you end up with one 12.8V 200Ah battery.

8 x 3.2V x 100Ah = 2560Wh
1 x 12.8V x 200Ah = 2560Wh

Things in series you add the voltage.
Things in parallel you add the amperage.

So with 2P you get 2 times the amperage. 2 x 100Ah = 200Ah.
With 4S you get 4 times the voltage. 4 x 3.2V = 12.8V.
The result is one 12.8V 200Ah battery.

If you create two batteries using two BMSes then you actually have a 4S battery in parallel with a 4S battery. The end result is 2 12.8V 100Ah batteries in parallel which gives you a total of 12.8V 200Ah. But it's made of two separate batteries.

 

[Wellfooled]

Thanks Rmaddy. That's what I thought, but was getting massive brain fog thinking about it last night. Oh well, NSTAAFL.