Noob question thread! 2020_Summer

Just PM me!

Dealing with intl through the site kinda sucks, but I am willing to do it if people reach out directly.

Thanks.

Does anyone know what the size is of the set screw for the tb clamps?

is there a guide/notes/thread on understanding amps/volts/ mAh…all the elctrical stuff in terms of battery/motor/esc/bms configuration. Ive left it way too long in learning what these things mean and practically have NO clue. did look on the battery builders forum, but it’s not the sort of thing im after

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I’m pretty noob too about this topic and before ordering the first parts of my build I ve read a lot of blogs and YouTube videos on electricity but this picture sums it all up

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this is what im after lol

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I think this might be helpful? I haven’t looked at it in a while though

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Amps = torque (how hard motor pulls) and heat, on every component!

Volts = how fast the motor spins, up to components rated limits!

Ohms can be generally ignored in setting up an electric skateboard, since it’s a property of batteries, motors, and wiring. All of which can’t generally be changed or are negligible in case of wires
Bonus:
Watts: volts times amps!
More volts, less amps for the same power, more efficient since everything generates less heat (except motors, they still pull those amps when starting up)

Now, an interesting quirk of vesc and motors is that at low speed, vesc can pull 1 amp at 50 volts from battery and deliver to the motors 50 amps at 1 volt. Ignoring losses, that’s 50W in, 50W out to the motors.
At 1 volt, motors will spin very slowly but have a very strong torque, which is necessary for starting up, then vesc will gradually pull more amps from the battery at the same voltage and deliver more volts to the motor as you speed up

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ok, so if my motors are 85 amps and my ESC is 80 amps, then my motors outstrip the esc’s ability to push them to fullest.
how do i calculate the amps of my battery that will be 12s4p using 30q cells (im guessing it’s neccesary to work out the amps (continuous?) of my battery?

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ESC ratings are generally battery amps, not motor, so the 2 numbers don’t compare directly.
Those rating are pretty wishy-washy anyways.
Your motors can run at higher amps than battery amps because of lower voltage.
Volts and amps don’t have to match on the 2 sides, only power does (minus the losses in between).

So in your case, there’s no bottleneck. You will push your motors to the max (amps aka torque), just not at higher speeds (aka duty cycle, aka voltage).

Battery max amps = cell max amps * p_count
30Q is 20 amp max, so your pack would be 80a etc.

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You set motor max to the maximum they can handle (or more. Cold is coming anyway. Worse they can do is start cogging before they eventually burn out)
Also 99% of the mosfets, starting from 4.xx versions, are 150A rated
Your bottleneck here is the battery. They sag a lot even at 15 amps each so i wouldn’t go much further than that.
At top speed, assuming no battery sag and that you’re using a dual motor/controller (also ignoring the 95% duty cycle and rounding it to 100%), your vescs pull each 50v and 30 amps from the battery and deliver to the motors 50V 30 amps.
Now, if you had an overkill battery, you could pull 50v and 80 amps (esc rating limited) and deliver that to the motors, but i can say for sure that ~40 motor amps/side is more than enough for the average guy passing 50-60km/hr

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Thanks. It all seems very abstract, but I guess once I have to program the ESC and input all the values, it’ll make more sense. Can I like download some sort of esc software tool to practice on?

So basically my Maker X MIni Plus, which is 80A (each motor) totalling 160A, will not even have half of it’s potential to be exploited because of the battery?

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ah this is helpful, so it’s the P-count that determines the max battery amps. so, for 30q at 4p it’s (like you say) 80a, 5p = 100A, 6p =120a etc etc…so with my ESC maxing at 160A i could get up to 8p. thanks, seems clearer. so the higher the P_count the more amps im feeding to my motors…which would result in…higher speeds*?

…and just t add another question - so youve mentioned P_groups increasing torque, but what about S_groups, what does that do? (at this stage in my build, S_group could be upped to 13 (though my esc may not able to run that…would have to check - just checked: it doesn’t)

*wrong - just more torque, if understood correctly

Higher acceleration.
(mostly; with some exceptions)

It’s a bit generalized and oversimplified, but:

p_count = acceleration
s_count = speed

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what are benefits then of using a focbox, or equivalent in terms of Amps, to build a street build with since most of them have 12s4p as a kind of max battery config (somne ocassionaly more) - and thus only use half the focbox’s power?. is it just safer to play with hardware that can take more amps? or is it the build quality/reliabililty that people are buying?

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The higher ranked ones will perform better (geo)thermally(lol), even if you’re far from hitting peak amp ratings.
Plus stuff like reliability, features, customer service etc.

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You need to take into account the cooling you’ll provide to that esc. The rated limits are in open air, or, “we tested it and it didn’t blow up” kind of thing. You’re way more better off if you use it at like 60 battery amps each and put a generous heatsink on it as well.
Once again, 30q’s at 20 battery amps look like they’re damn near dying. Even 15A is a real struggle for them. Maybe look into a 12s4p p42a/40t for a real 60A/side pack

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Thought exercise…12S setup at low throttle vs 6S setup (with double the cells per p-group) at high throttle for lower speed cruising.

Is one superior? Assume whatever else is needed to make this comparison.

Both should draw about the same amount of current from each cell in the battery pack but are their non-linear things going on somewhere that make 6S at full throttle different than 12S at 1/2 throttle?

ESC efficiency issues? Heating? Gearing ratios?

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I’ve not bought the cells yet, but unless I get a bespoke enclosure made I have to stick to 18650…so perhaps other cells are better than 30q here? The VT6 ones perhaps?

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The answers to this are buried all over the forum. It really needs a good post on the topic.
I need someone else to answer better,

but “it depends”. It’s a big tuning problem of what gear ratios you can manage / fit. wether you hit current limits of wiring, ESC. etc.

There are those who insist more voltage is better for all the things. and then there Moe Stooge racing… running very high amps at 8s voltages with in runner motors.

adding:

and I should point out drawing the same amps at half the voltage is half the power (watts). so to deliver the same power the amps won’t be the same. if you gear for the same top speed, the 6s pack will pull twice the amps to deliver the same speeds/power/torque to the gournd. assuming the equip can handle the higher amps.

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In terms of performance the 30Q and VTC6 are very close with the VTC6 just a touch better. Probably not noticeable in actual use. Stay tuned though, posting a test report in a couple of days with another possible option.

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