xl-frame said:
Need to build a 48v battery that I will be using to convert a bike with 20" moped rims and a Leaf 48v 1500w 5T hub motor. [...] If my math is right, in order to accomplish this I need to build at least a 14s8p battery.
For a 48v battery you need a 13S config; 14S will make it a 52V pack. It is however something worthwhile to consider, as long as you bare in mind that the other parts of your setup should be compatible with that. (It will increase the capacity and likely decrease discharge rates and positively affect speed.) How much cells you need in parallel depends on the discharge characteristics of the used cells and the capacity. Notable is how it 's pretty much capacity vs discharge current.
Given the 1500w motor you probably will have some peaks of up to 25-30A or maybe even have a high discharge rate if you ever consider higher speeds than the earlier mentioned 15-20mph. For that a 5P setup of the Panasonic NCR18650B (3350mAh) will be sufficient, as it will perform well with a discharge rate of 6.7A per cell. The NCR18650PF (2900mAh) does well with a discharge rate of 10A, so in regards to that you only need 3 in parallel. With other cells you may find they perform much worse at such high discharge rates and affect the relative capacity badly, so it's advisable to use more in parallel. Also a high discharge rate may affect battery life negatively. (if you only drive 15mph continuously the average discharge rate will be relatively low though.)
In regards to price vs capacity the Samsung INR18650-29E (2900mAh) is cheaper than previous mentioned cells. Also at a 3C discharge rate (8.25A) it's relative capacity is still 92%. Then again you actually need a lot more cells to build your 48v/30Ah pack, which may make manufacturing the pack considerably more expensive.
Another factor to take into consideration is the influence of temperature on the relative capacity. When you use your e-bike in winter, with temperatures slightly above zero, their relative capacity will be a lot lower then at room temperature.
I'm not about to suggest you any cells, as doing your own research and comparing datasheets is actually real fun. I personally like the NCR18650B cells as they are really versatile for all kind of battery packs. I would buy them from
NKON as they for sure sell genuine cells and are quite often the cheapest supplier of cells. (They ship internationally.)
In regards to building the pack I would keep in mind that the thing should be rigid and it's mechanical integrity should be guaranteed at all times. If you use nickel strips, please bare in mind the wrap around a cell is really fragile and you want to make precautions against shorting. Either by using a cell holder or by using those self adhesive isolators. Personally I also care about using good silicon wire and crimped connectors, which do met UL/TÜV standards. (And I totally advise against the Deans plug crap.) If you want to use tape for certain things, you better use kepton tape instead of regular tape.
Bonus: A nice tool for calculating how much energy you need to perform your cycle activities, is to be found
here. Also please note that the correct unit for capacity of a battery is watt-hour. (And with a reason.) Ah is perfectly fine however for comparisons and makes head work a lot easier.