If I was go to for 18650 cells, I had this idea of having two 20ah packs and "hotswapping" them. This way I could get full charge cycles from them, and since I have to remove from the bike anyways and carry to apartment to charge, it would be even lighter weight and more manageable.
Is there a post or spreadsheet that has current 18650 cells with links on where to buy them? I'm trying to get my head around the continuous and peak Amps rating each cell has for my project.
I realize the BMS will be the limiting factor (prob going to get this one https://goo.gl/9UpLdo
) but I still need to decide on what cell to use
Looking at this page
And prices from "Queen Battery Supplier" - got this from another endless sphere post
3500-mAh, NCR18650GA, Panasonic-Sanyo $4.40 usd / cell https://goo.gl/VjWXdU
2900-mAh, NCR18650PF, Panasonic $3.40 usd / cell https://goo.gl/guB5ao
3400-mAh, NCR18650B, Panasonic $3.60 usd / cell https://goo.gl/kDeZcE
20A__2500-mAh___25R Samsung $3.48 usd / cell https://goo.gl/EHYXJ2
15A__3000-mAh___30Q Samsung $4.52 usd / cell https://goo.gl/Ekt2HJ
So math time doing one 20ah pack, will need 20s just to get 72v so its just a question of Ah and current output. Do I just need to get cells in parallel that produce as much cont. As what I need as peak amps? Then my BMS limits it?
3500-mAh, NCR18650GA, Panasonic-Sanyo 20s6p=21ah 10a per cell x 6 = 60a continuous 20x6=120 cells=$528 for 21ah
2900-mAh, NCR18650PF, Panasonic 20s7p=20.3ah 10a per cell x 7 = 70a continuous 20x7=140 cells=$476 for 20.3ah
3400-mAh, NCR18650B, Panasonic 20s6p=20.4ah 10a per cell x 6 = 60a continuous 20x6=120 cells=$432 for 20.4ah
20A__2500-mAh___25R Samsung 20s8p=20ah 20a per cell x 8 = 160a continuous 20x8=160 cells=$556.80 for 20ah
15A__3000-mAh___30Q Samsung 20s7p=21ah 15a per cell x 7 = 105a continuous 20x7=140 cells=$632.80 for 21ah
I know there will be come internal resistance, but surely there is a rule of thumb when choosing cells when you have specific power requirements?
Or is my only real option the Samsung 30q since its providing 105a continuous (which is what I need peak), which is unfortunate because its the most expensive.