in pavel garmas’s VESC tutorial video he says that 18650 battery’s should choose this 3_0__4_2 option
but doesn mentioned what 21700 battery owners need to choose. ive got a 12s4p 21700 40T batter, can someone advice me on the settings i need (and even better, point me to guide to setting up my VESC…im very n00b to this part)
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I don’t believe that the size of the battery matters here; I think it’s just the voltage that the cell is rated for; i.e. if your cell is meant to go up to 4.2V for that option, then choose 3.0-4.2, and I believe the second option has a lower range for another cell chemistry. The 40T charges up to 4.2V like most of the 18650 cells we use, so you’d choose that one. As for Battery Cells Series, it’s pretty self explanatory – in your case it’s 12, and for Battery Capacity you want to input the total Ah of your pack. So for a 4P config of 40T, it would be 16Ah since each cell has a capacity of 4000mAh.
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very clear, cheers mate 
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Same choice for 21700.
It’s the chemistry that matters and not the form factor.
edit: answered already by @YeetMeat
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What @YeetMeat says is correct
I also personally don’t discharge my cells down to 3v, I cutoff at 3.2v. I just set my voltages manually after configuration
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I second this, strongly. You’ll only destroy one battery before you feel the same. 3.2 is even pretty low.
Check this out:
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Yeah that’s my cutoff end, I start 3.4 end 3.2
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These settings will maximize battery life and minimize failure risk.
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Eeeeek I thought 3.0v hard cutoff was normal/safe 
Time to change before my first ride…
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There is no sharp line. The lower you go, the harder it is on the cells. The higher you go, the less usable energy you have.
Same with the full charge voltage. 4.2 is fine, but some people only go to 4.1 or 4.0, to prolong the cycle life even more at the expense of less range per charge.
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By the time you get to 3.4V, nearly all of your range has been expended. If you have any unbalanced p-packs, those could be lower, even down to 3.0, at that point. Pushing your battery further than that adds a crapload of risk for very little benefit, in my experience.
Especially not when a Lyft is so cheap, if it ever comes down to it. Range Anxiety is a very, very real thing. But it’s mostly frivolous. There’s not much to worry about. You’ll almost never run out of range, and if you do, skateboards can be kick-pushed and a Lyft (or Uber or taxi) costs only a few bones and a few minutes, in the super-super rare event you’d even need it.
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absolutly this.
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For the mechanical engineers out there, how should tolerance between precision milled pieces be set? For example I need to design a base plate with the hole to fit the kingpin (3/8" diameter), what would be reasonable tolerance for the baseplate hole?
Nice build! I bet your clearance is a lot better with those wheels. Going to be running some thane so hopefully it won’t be an issue
It depends on the tolerance of the kingpin.
With any precision design, the tolerance is set by the least accurate part.
Doesn’t matter if your stuff is +/- 0.0001", if the thing it has to fit is +/- 0.1".
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I can’t get a couple of groups to charge past 3.8 - 3.9 I don’t know if it’s a bad charger or incorrect settings. The second screen shows status voltage 3.35V I don’t know what that is. both the charger and multimeter reads the correct voltage. I’m charging at .5A charger is the IMax B6 cells are 30q in a 12s6p config.
is this normal, how can you prevent this from happening?
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No it’s not normal, he’s disassembling it like an idiot
His cutters are going right through the outer casing and direct shorting the batteries. You can disassemble without any sparks. In my videos disassembling the EMC 26650 packs I only had one or two sparks and it was just clumsy-ness
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Yeah, looks like his screwdriver went through the shrinkwrap and shorted the cell bodies together. There should have been fishpaper in the exact spot the screwdriver was in, this is why.
PVC shrinkwrap that the cells are wrapped in is very fragile.
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the capacity of a 6p group would be 18000mAh, should i set my capacity limit to 18000mAh when charging a single p group?