hi
just building a 12s 8p battery just wondering how far you can go on this average cell is 2000ma
made out of recycled 18650s
thnaks
Battery would be, 43.2v 16AH which equals to 691.2WH, and the average urethane setup draws 25wh/mile so you would get around 27.65 miles
Calculations done based on speeds of 22~mph
1 Like
I would think twice about using recycled cells. 12s8p pack is a lot of work to build properly and you’ll be tearing it apart sooner than you think if your using junk cells.
7 Likes
Thanks
Do some research on recycled battery’s, you may change your opinions.
When you did your research, what type of batteries where they used in making eg powerwalls?
18650s, most people use them in powerwalls, but you can pretty much use any type of chemestry as long as you use an active bms which will increase the life of batteries.
Do you know what is the average amp draw per cell on a powerwall?
1 Like
I have done real research, by actually using them. It’s a waste of time and money.
You can build a pack with the same capacity using less cells, which just about evens the cost out. Which is exactly why you see very little packs made here with recycled cells. The ones that are made do not last very long.
3 Likes
This is a great Esk8 calculator for your project… Probably the struggle will be keeping P groups in balance manually…and checking your cells periodically…
I’ve been thinking lately : what if our way of calculating our usable Wh and real consumption is way wrong?
Nobody uses a cell from 4.2v down to zero, we only use down to 2.7v at worst and in most case we don’t use them below 3.4-3.2v (some even cut at 3.7v with big packs to keep long cycle life).
Which would mean that the total Wh of the pack is correct but the effective Wh is way less. Consumption should also be calculated on this net number instead of gross Wh.
It doesn’t change a thing irl tho, apart from being able to predict more accurately the range no?
Example : Let’s say I have a 12s8ah pack. Full voltage gives me 403wh (Nominal voltage gives me 355wh).
But that’s for full discharge. If I cut discharge at 3.4v (so I drain like 0.8v/cell from a full charge 4.2v cell or 9,6v from 50.4v to 40.8v), my effective usable Wh drops at 76Wh.
1 Like
lots of other factors come in play as well, temp had quite an effect on a cell, and theres hills ect
i limit my cells to 3.4v and 4.05, for longevity, but for this battery pack i may widen it for a longer range
1 Like
Maybe a little bit off topic for this thread but you calculate your watt hours using nominal voltage never use the full voltage. If you do this then the watt hours calculated and the actual real world watt hours you can use should be similar depending on your cutoffs and how hard you run the battery (because if you run cells at a higher current throughout that discharge cycle you end up getting less watt hours out of that cycle). So calculate how many watt hours you have based off nominal voltage of your battery and go out and do a range test using a Bluetooth module and app that you can track watt hours used in and see how many real world watt hours you use and I’d bet the theoretical watt hours and real world are similar.
3 Likes
Brand new pack 12s7p 21,000mah samsung 30Q
200mm pneumatics, twin 4.10, 192kv sk3s. 5.3 gear ratio, 70kg rider.
It depends on the terrain and how you ride. I did the Brean Down Way the other day around 15-16 miles and I only had 30% remaining. Id have been lucky to get 21 miles. I make that around 43wh per mile! The route did have normal road, gravel, sand, rocky paths and hills though. https://danielz.uk/brean-down-way/
Your pack wouldn’t have got me very far at all that day lol.
1 Like
Not very far if you’re using recycled cells and not matching the internal resistances.
2 Likes
A 12S8P with new cells will go “jelly legs” far. There is a calculator linked from the top bar. Use a lower efficiency for pneumatics or “airless” wheels. Regular polyurethane longboard wheels, about 90% efficiency.
2 Likes
Wow small world, my mrs is from Berrow and I know this area well.
2 Likes
I been building packs for a while, yes each cell is balanced very well.
Really wasnt sure about range but id be happy with 10 miles, i was only intending going a couple of miles anyway.
Then you should try a 10S4P, it will be MUCH lighter and safer on your electronics than a 12S8P.
10S4P will typically go 10 miles (16km) no problem at all. Might be the upper end if it’s only 2Ah cells that are used, maybe go 10S5P 
2 Likes
Im going to use 6374 190kv motors i think