So the 20700a is 3300 mAh and 30A, and the 20700b is 4250 mAh and 15A.
How do these numbers translate to use in an eskate when it comes to range, power, and top speed?
Motors will be 6374 190kv with dual escapes.
You need 60 amps at minimum so you need to figure 2p or 3p or whatever so you get the amp delivery you want.
I’ve never used those specific cells but here’s some perspective…
The 30q is rated at 15 amps but performs very well at 20a constant so a 10s3p is usable, a 10s4p is way better. The 25r is rated at 15 amps so you really need at least a 4p to be usable, a 6p is pretty nice.
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@Taliesin Given the same number of cells, the 20700a would give less range but more power. Vice versa with the 20700b.
That’s assuming the same number of cells. But to have enough current, you’d need more 20700b cells as well, so a 20700b pack with enough current would have a MUCH higher range than a 20700a pack, and also be larger.
The 20700 cells are still fairly expensive, so it’s probably still cheaper to go with 18650s for now. If you must go for 20700s, go with the A cells unless you’re going for a HUGE pack.
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Copy that. Would a 12s4p be considered a huge pack? Or should I be considering a 12s8p if I’m going to go with the 20700b’s? I’m leaning towards the b’s due to the range aspect.
4p would probably be enough, maybe 5p. 8p would be absolutely huge, 1.5KWH.
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4p of 20700A would still give 586WH, which is still a very large range, and it would give you a lot more power to feed those big motors.
most boards with 'thane wheels get 10-15 wh/km, so 586wh would give you something close to 40-50km of range, depending on your board.
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I think I would be satisfied with 40-50km of range. But let’s just say I went with the B’s, getting 1.5KWH, that’s three times as much, so would that basically be like 120-150km of range?
Yep, and the pack would weigh 13.5 pounds. It’ll be a beast.
And how much noticeable difference in power/top speed are we talking between the 2 if we were going 12s4p for both?
I’m not expecting to ever need to go faster than 30mph, and I’m most comfortable between 20-25mph. I also don’t need to climb any hills steeper than my backfire g2 already handles.
I’m not power hungry but if I went with the B batteries and felt like I wished I had a little more power that would be a big chunk of money to reinvest.
You won’t notice any difference in top speed, only acceleration. (and maybe braking to some extent)
With either setup, you’ll have way more power than the backfire had, even the B cells will be able to provide about 4x the power, and the A cells will do closer to 8x.
With the B cells, it might be worth considering going with 6355 motors instead of 6374, since you’d only be able to feed each motor 30 amps, whereas if you were using A cells, you could feed each one 60.
My last build had dual 6355s at 40 amps each, and the power and torque were awesome - I couldn’t stay on the damn thing if I tried to go full throttle from a standstill.
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Ok awesome really great info, thanks so much. I already have my motors but I’ll look into possibly getting some 6355’s as well.
Don’t get me wrong, it does no harm to run motors at less than 100%.
Also keep in mind that you can upgrade your battery pack later if you feel the need, by adding another parallel group or two.
Is combining cells a thing? Like could you wire A’s and B’s in the same pack or would that not work/stupid idea?
That wouldn’t be a good idea, but adding more of the same cell to a pack is acceptable - e.g.going from a 12s4p to 12s5p.Mixing different types of cells isn’t recommended because they don’t share current evenly.
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These cells are good for small packs, but for larger ones they are just too expensive
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Ok right on, thank you.
Also true - The advantage of 20700 cells is that they have about 50-60% more energy than an 18650, so you can use fewer of them for the same performance. Doesn’t make too much sense to build a huge pack with them though, when you could do it with more 18650s for cheaper. 30Qs are available for ~$3.50.
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Yes that looks great! Where did you get the battery holders I really like those!