Electric Skateboard Calculator | ESK8 Calculator - What size, Motor, Battery, Wheel, Belt to use?

Oh right… :frowning: NVM means my board can spin car engine shaft :smiley:

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On the subject of torque, you could the force that the wheels put to the ground, way more meaningful when comparing board with different wheel sizes

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I have some thoughts regarding comparison between multiple things but that’s for later on :slight_smile:

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But there is no such thing as average or max watt hours. The pack has a defined amount of total available energy.

Yes, but you know that fully charged on will discharge more Wh than your Wh rating on nominal cell voltage?

EDIT: that’s especially the case with lipos :wink: As nominal cell voltage is 3.7V but dead is at 3.4V :wink:

No it will not - wh is energy what you are talking about is power (at least I think that’s what you mean) - that’s a different thing. Also you’d have to look at a lipo discharge like I showed above which will show you that the energy inside your battery will be estimated very well with the formula nominal voltage*capacity.

Yes, I understand but why then I consume more Wh from battery according logs than Wh calculated according to you?

Thats interesting - How big of a difference are we talking about? I am just saying that the wording is not right with max and average Wh for a battery - there can only be one total energy the pack has. About the topic whether nominal voltage*capacity actually represents the energy in a Lipo well, is a different story and I am happy to discuss and learn.

If you have suggestion for wording I can change as I am not specialist in naming things :smiley: But regarding capacity I am usually getting near 900Wh so according nominal voltage another whole hundred 100Wh :slight_smile:

There is something wrong somewhere then

What cells are you using and what configuration? Energy is simply work integrated over time, what could be wrong is your nominal voltage, for example, 3.6V volts works well with Li-Ion, but if you use that with Lipo to do a roughly energy estimation your result will be less than what actually the battery can store

nah I use 3.7V for nominal and Turnigy Graphenes :slight_smile: Maybe it’s Graphene making magic don’t know :slight_smile: I just wanted to add that number for myself as I planning to use the same packs in future projects too :slight_smile:

My guess is that your capacity is just slightly higher than what is printed on the box. 100Wh at 900Wh is roughly 10% - not unheard of that a say 5000mAh Lipo actually has 5500mAh especially considering you are using the more expensive graphene ones. I’d say that the formula still holds and with brand name Liions we can be sure that the capacity is not 10% above the rated one. For HK Lipos etc. capacities might be a bit off.

I’d just use the nominal*capacity calculation in your calculator and simply call it energy (or battery energy or total pack energy or whatever you want that gets the point across).

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^suppose i’ll be climbing 1.8miles on a steady 5% grade…

i have 4x 190kv 0.05ohm motors & 83mm tires, 120a motor current and 60a battery current limit per motor, & 13S (48.1v)

what’s my maximum top speed up slope and what gear ratio gives this top speed assuming 0.6m^2 frontal area, 0.75 drag coefficient & 200lbs?

?

1000char

i have no idea! :smiley:

This looks great!! Thank you

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I have no idea too? Did you post it as a question?

Maybe this could help

Taken from a go kart forum

Force Hill = Weight Go Kart * SIN(Angle Hill)

The typical hill is 10 degrees and the sin for 10 degrees is .17

So the Balancing force to just hold the go kart in place on the hill is for example:

(228 (gokart) Lb + 185 (person)lbs )*.17 = 70.21 lbs

The next step is to calculate what the go kart will do with the horsepower it has. So we go through the calculations covered in Go Kart Building 201 and come up with a force that is pushing the go kart:

Force Go Kart = (Te* Rd/Re*Rw)

Te = Torque Engine = 59 in-lbs Rd = Radius Drive Sprocket = 4.3 inches Re = Radius Clutch Sprocket = .60 inches Rw = Radius Wheel = 6.5 inches

Force Go Kart = 48.41 lbs

As you can see the force that the engine will push the go kart is 65 lbs, to climb a hill it must put out 70.21 lbs. The go kart will actually go backwards down the hill with this set up, because the amount of downhill force is greater than the engine can deliver.

The go kart to be exact will go down the hill at – 5lbs/12 slugs = .41 ft/sec^2 which would appear like a slow crawl backwards.

Says my max speed loaded would be 58mph but I’m expecting 50mph in reality.

Depending on capacity but by the time you reach your top speed your voltage will be probable down a bit which would limit your speed :slight_smile:

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