Unreasonable E-MTB build - Me too, I want to faceplant on dirt at 60km/h (and commute everyday too)



I’m Boubak, a software R&D engineer from France :).

From the very beginning I wanted to build something that make me sh*t in my pants and commute because as somebody working in Paris, I hate the subway and I really prefer to be outside, exploring the city everyday.

My first attempt was a build based on a loaded tan-tien longboard with paris trucks, i-don-t-know-the-brand-anymore belt motor mounts, APS sensored 220kv 50-ish mm 2200w motors (don’t remember to be honest), 2 4.7 vesc and 8S li-po battery pack.

It was great, really!

But I started to neglected it since I realized that it was inconvenient:

  • Flexible board with battery pack under, so I never found a satisfactory option to mount other than the temporary rope+plywood+plastic-collars
  • Not waterproof at all
  • Not offroad enabled
  • Need to get off the board to get on sidewalks
  • Hardware vulnerable under the deck
  • Could be more powerful

So I couldn’t really use it daily, and no offroad at all (I was raised a snowboarder, I want to do offroad, I need it…).

My goals with this project

So, I wanted to ride something more bullet-proof, rain-proof, offroad-proof, with the hardware uperside, more powerful and that can get on sidewalks.

So, after reading a lot of post on this forum (especially from @NoWind and other no-limit E-MTB builders ), and after spending many months viewing @Nowind youtube channel (and dreaming I was him riding his machines :smiley: ), I decided that it would be an E-MTB ! \o/

My BOM, so far…

Considering I’m 175cm, weight ~75kg and carry a 13kg backpack

Board : Trampa HolyPro 35 16 ply with infinity or vertigo trucks, superstar hubs and trampa threads or primo alpha

Motors : APS C8085 sensorless 170kv with AS5047 magnetic encoders

ESC : Dual V6 esc from Trampa or Flipsky, best if with integrated anti-spark switch

Battery pack : 12S Li-po setup (4 x Compact 6200mAh 6s 40c Lipo Pack w/ XT90) with a 200A BMS from Bestech (like the HCX-D575 )

Remote controller and receiver : my hobby remote and receiver

Motor mount : Direct drive (with helical gears?) from @Nowind, if possible with custom motor cages with AS5047 mounting capabilities ( is it possible ? )

Additionnal stuff : Custom aluminium waterproof battery enclosure and custom aluminium heatsinking VESC enclosure CAD-ed by me (I need to train more on freecad) and manufactured by any prototyping company willing to do it. A lot of 8AWG and 10AWG silicon wire. Maybe bluetooth telemetry.

A lot of questions

So here is my plan.

And I’m sure about almost nothing XD.

And I ask me a lot of questions:

  • What about risks of frying drv with transients on a VESC with a 12S ?
  • Will my custom battery enclosure ( that I would between my foots) prevent the board from flexing ?
  • Is it really possible to make it rain-proof ?
  • Does 2 C8085 motors fits with motor mounts and cages and AS5047 housing on a standard Trampa Infinity truck
  • Is is possible to dissipate enough heat by screwing 2 VESC on an aluminium box (with thermal paste) to run them at constant 100A max motor current in BLDC?
  • The same in FOC ?
  • If it works, will I die in the 2 weeks following the completion ?

What do you think about it :slight_smile: ?



Opinion on batteries: from reading the forum for almost a year, the consensus is that lipo C rating is overrated. That means get more than 60C discharge, preferably graphene batteries. If you go 10S it will safer for the vesc and with proper gearing, you could get the same top speed.


You are completely fine gunning 12s on vesc 6 hardware. I am a fan of 12s 8p 25r liion packs with NESE modules. Not sure if range is a concern for you but if it is…this will definitely cover what your looking for

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@okp @Riako

Both from france. Does a lot of off road / street riding. Maybe can spare a minute to give some tips


Hey @boubak. okp here Join the ESK8FR shredding session group rides that I organize in Paris. You’ll meet diversity with a bunch of people riding different boards !

On my side, you can either get parts from me (unikboards.com) or from Jens (http://e-toxx-shop.com) or from some other folks and I can build you or support you in the build of your board.

I always ride 12S on VESC, FOCBOX on my side but my mate @Nowind will also advise you.

In any case, you cannot go wrong with @Nowind stuff. I just received a MBS Matrix 2 direct drive from him to build a board and I can tell you, that you cannot buy happiness but this is pretty close.

Join us on the No Car day in Paris this week for some hardcore riding :wink:

Cheers !


Thanks everybody for your replies !

@Grozniy :

For my battery pack, I didn’t cogitate at all, I just choose the same initial setup as @Nowind :slight_smile: thinking that if it works for him, it will for me.

I will take a look at graphene batteries, thank you :slight_smile:

My main goal is more having torque than top speed (even if top speed is cool too) so I fear that If setup a 10S battery pack, for the same top speed, I will need a higher KV motor. And for the same power it will draw more current ( so my electronic setup will maybe suffer more or need more heatsinking ). Another problem is that I want to go with the @Nowind Direct drive unit, so the gearing seems constraint by the size and shape of it.

@Trdolan03 :

Even if I draw a lot of current ? (like 100A per motor). If that’s the case, it’s very cool !

About the battery pack, my main concern is not really the range, more the capability of giving a lot of current and the size. If I can ride 15-20 kms on a single charge accross Paris, It’s perfect for me. Do you think it’s achievable considering the build I want to do ?

I will take a look at the li-ion elements you advised anyway :slight_smile: , Thank you.

@Okami :

Thank you for the tips :slight_smile:

@okp :

I will join with pleasure as soon as my build is ready :smile: ! ( I didn’t realize there was such events from the French esk8 community ).

I think I will a lot a questions to ask you, thank you ! Do you have a physical shop in Paris ?

Yes, seems to be the kind of high quality stuff you want at least to take with you in the bed in case you need to look at it because you can’t sleep, continuously thinking about it :stuck_out_tongue_closed_eyes:

I can’t since for now I haven’t any esk8 build complete anymore >< (I dismantled my previous one). I need to live in shame being a pedestrian…

Cheers !

It will not if you design it right. I split mine to two separate boxes and both I´ll bolt with 4 bolts only in the middle of the box. Between the box and the deck I´ll add a 5mm spacer which will give the box some more space on the corners. you could also velcron the battery to your deck. there is pretty strong velcron available and it always gives some room if board is flexing.

And second, yes for sure it´s possible to get it water prove. Just seal it right. I know you want to design your own box, but just wanted to notice that a lot of guys use modified pelican box as battery storage.

Maybe it´s just me being a sissi, but I wouldn´t have a good feeling with my batteries in a aluminum box :sweat_smile:

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@Andy87 :

Thank you for your reply :slight_smile:

Ok, I thought about something in that spirit, but I don’t understand the “4 bolts only in the middle of the box” part. Could you please elaborate ? ( or better, put a picture of your setup :stuck_out_tongue: )

I also thought about three more options :

  • Adding degres of freedom to my box by anchoring it with rods and ball joints at the 4 bottom corners (a little bit like the anchoring of cells on top of offroad trucks)
  • Putting my battery pack box at the opposite of the VESCs box, on top of the front truck --> Big advantage of balancing the masses of the board
  • Splitting my battery pack in two separate boxes : one on top of the front truck, the other between my feet --> hybrid between your proposition and my second one but meh, not convinced…

My main concern with this is having a 200A BMS heatsinked properly inside my waterproof batteries box :confused:

I want to avoid this solution because I never found the right form factor, and it will be hard to heatsink properly, I think. And beside that, I don’t like the look of this solution :confused:, useless handle, round corners, not well integrated in the final product…but that’s just personnal taste :slight_smile:



horrible picture but I think you get the point with only in the middle.

I now don´t get your point with the batteries on top of the back side of your vescs on the front truck… You plan to install the vesc on the front truck? As kind of balancing the board if I understand right?

In general a good idea, just be aware that with long wires you can get voltage spikes which can fry your vesc. Especially the wires from the battery to the vesc should be as short as possible. If you need longer wires, add some capacitors which can flatten the voltage spikes.

One thing I also wanted to ask you. Do you have any experience in how much amp you draw on the road and off road? 100A per vesc is a lot (especially constant) if I didn’t calculated wrong with a 12s it would be about 8,8kW for your two motors. I doubt that there is a hill in paris which would need that power constant to climb up. just don´t understand the reason behind. 100A constant means also bigger wires, shorter wires, more heat sink etc etc (by the way you know that the VESC 6 in the housing it comes only can handle up to 60A constant) lot of extras which you probably will not, never ever use. You could ask here in the round some MTB experts, what´s there average amperage. I can only say you what you will need on the flat road and that´s far away from 200a

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@Andy87 :

Thank you for the drawing, it’s now perfectly clear :slight_smile:

My explanations were confusing, my bad ><. What I wanted to said is that I could mount the batteries box on top of the front truck and the VESCs box on top of the rear truck. With this configuration there will be kind of same amount of mass on the front than on the rear :slight_smile:

I didn’t know that :open_mouth:, what is the electrical principle involved ?

My previous build was with a longboard, so only a road one without telemetry, but by slowing the wheel mechanically on my test bench with kind of the same amount required by the steepest hill I know, the biggests spike where around 45A per motor.

I’m aware that I will not need 100A constantly, it was more to have a big safe margin considering that I’m quite demanding on my gear when doing a board sport and that I don’t want to be constantly monitoring the health of my board if I suddendly decide to go hardcore offroad. In the spirit of the @Nowind riding style I guess :smile: (that’s also why I’m considering the same kind of current values)

Concerning the two VESC 6, my plan is to bolt them on a bigger heatsink/enclosure with thermal paste I already planned to go big with wires.



Induction. It also helps to place the plus and minus as close to each other as possible. As the forces work than against each other and minimize the effect



Thank you for the explanation. I didn’t think it could have such a noticeable effect with wire of just 1 meter length.

Anyway after second thought, I don’t think I can put a 12S 2P 12400mAH battery pack with BMS on top of the front truck, it will be too big.

Can you elaborate please ? :slight_smile:



It’s just because aluminum is electrically conductive. Sure you can heat shrink everything or cover the inside with neoprene than it shouldn’t be an issue. I just prefer non conducive materials like fiberglass or plastic

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Ok, I thought maybe there was something more esoteric I’m not aware of. I plan to do a proper insulation of the inside of the box.

By the way, what about security holes or exhausts in case of battery fire ? Is it a common practice amongst the esk8 community or does we just consider we can take the risk because it is very small because we take care of battery pack/we have BMS ?

I don’t remember to have read anybody post about that ( but maybe I didn’t search hard enough )



I had a fire and it burned down the sealing and plastic parts of my enclosure… Don´t know how it would be if you make a full sealed aluminum battery box. You could make some holes which you cover with neoprene or silicon, it will meld away fast and the pressure can release.

PS: get some fire protection covers, or a fire extinguisher or a big gallon of salt water for your home!!! Better all…if you work with batteries, doesn´t matter which, it should be standard to have some protection close by.

It´s not small at all!!! don´t take it on the easy side. 300+Wh are a lot of energy if it´s get released in just some seconds

What I mean by small is “very unlikely”, it was confusing :slight_smile:. I very well aware of dangerousness of a battery fire.

I already have all of that in my shop, that’s not the first time I work with big batteries :smile:.

I thought about something in that spirit, I will do my research on the subject.

Do you know if someone on this forum made something similar?

P.S : Don’t take the tone of my posts as a form of inconsistency or a brainless attitude, I’m just free of any assumptions on the questions I ask :slight_smile:.

for now I don´t know anybody who made an aluminum on board mount. most guys here just use the plastic boxes or use a tray for under the deck. you could look through the “just pictures” thread, maybe you will find somebody who already made something similar.

no problem about the posts, just ask your things. better to discuss things and get ideas than just start work and in the end need to redo the half again…

Good idea, thank you !

I agree :slight_smile:, but I wanted to specify my mind state, I know I can sound very candid with my way of asking questions.



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For me it’s fine. Keep on going :stuck_out_tongue_winking_eye:

Fensh Mountainboards shop used Alu box. Look at Overion.fr he make central and rear Box, full Alu, made by itself, top plate customisable color (anodising) and other custom. All in the box, nothing else :ok_hand: like it so, just a bit heavy of curse VS Carbon fiber or like that.


https://scontent-lhr3-1.cdninstagram.com/vp/dcfd411a45a1b68ba219e151eb655346/5BE95B2E/t51.2885-15/e35/35616484_1083736291782633_4730868045176635392_n.jpg?ig_cache_key=MTgxNDQ1NTM2OTc0Nzc5ODMwOQ%3D%3D.2 There is also Willozboard with a compact 12s5p bms in a small Alu case. This two produce and ride eMTB since a long long time already (around 2007), before we start looking info on forum or even think about it :star_struck: they’re kind of genius with gold-hand. https://wib-sport.com/317-large_default/e-mountainboard-willozboard.jpg https://scontent-ort2-2.cdninstagram.com/vp/c61fa254283bef95eea953f5fa2a9df6/5BEE8F87/t51.2885-15/e35/22860841_1904241743225453_6229204623752691712_n.jpg