Designing my own battery - Some Detailed Questions About Cells

Hey Guys,

I just want to start by saying I’m a complete noob to all this but have been learning lots in my research. I have come to some conclusions that I would really appreciate more experienced guys to check for me.

So I managed to get an old NLS Pro for cheap in great condition but the battery was dead. I’m salvaging the old cells and then will attempt to sell them but my initially idea of replacing the dead cells with new ones doesn’t look like a good idea. Therefore have decided to build a new battery.

The original cells are Samsung 40T (4Ah) in 10S2P config. The max cont discharge of the VSC is 30A therefore need 15A (min) per series of the battery.

I’ve been doing a lot of research and have spent hours on AliExpress which is a mine field for batteries but managed to find one legit company.

So I am looking at the following three cells:

  1. 18650 Battery 2500mAh 3.7V High Discharge 10C 30A Cont Discharge (10-15 mohm)
  2. 18650 Battery 3000mAh 3.7V High Discharge 10C 30A Cont Discharge (12-16 mohm)
  3. 21700 Battery 3200mAh 3.7V High Discharge 10C 30A Cont Discharge (6-10 mohm)

So as I previously stated the max draw on current I will require will be 15A therefore I have searched YouTube and found the following specs for the battery tested at 15A continuous current. They all seem to be Russian testers but I managed to extract the key stats from the non English vids:

  • Battery (1) Energy: 7.9Wh, Cap: 2479mAh, Timing: 09:55 (Max Heat 75 C)
  • Battery (2) Energy: 8.1Wh, Cap 2637mAh, Timing: 10:33 (Max Heat 78 C)
  • Battery (3) Energy: 10.4Wh, Cap: 3042mAh, Timing 12:10 (Max Heat 51 C)

I know the max heat is quite high for the smaller cells but this was continuous at 15A which isn’t likely in reality.

Obviously this isn’t as comprehensive as a full curve but it’s a good rough idea at the max current I will be drawing.

Now, the reason I’m considering (1) and not exclusively (2) is because it has a similar capacity and lower internal resistance and is cheaper. However looking at the stats maybe (2) is the superior choice. The idea is to make two batteries from either of these cells which would be ideal as most of my journeys are short and when I have a longer one I can just carry the extra battery and swap it out.

Battery (3) obviously has a higher capacity and almost half the internal resistance. It’s also bigger and heavier but it’s the size of the original cells that were in the board. Battery (3) is pretty much the equivalent of Samsung 30T cells and the tests done on it came out good.

So that’s quite a detailed explanation of my research so far. What do you guys think?

Lastly there is one final option which is a lot more costly and probably makes more sense to just go for the 40T but there is a fourth cell that I was considering but it’s almost the same price as the Samsung Cell or Molicel equivalent. Let’s call it cell 4:

YouTube Tests of the three cells (in Russian):

Thanks for any/all Help!!!

1 Like

Don’t buy cells from AliExpress.

Don’t trust numbers from the manufacturers. Their objective is making money, and higher numbers sell more stuff.

Do lots of research to find the best cells as tested by independent folks unaffiliated with brands.

Mooch’s test results are a great place to start.

Thanks, a lot of people have said the same thing to me so I went for MoliCel.