DOUBLE TROUBLE - A pair of Urban Cruiser’s

!i!i! WARNING !i!i! - this may be the single longest post on the site so far :wink:


I completed my first build “BIG TORQUE ” over a year ago and feel like many lessons have been learnt during that process. I was planning some upgrades but small things i wanted to change resulted in needing to change a lot of hardware.

A friend with a boosted board also decided that he wanted to go the DIY route so we decided it might be worth it to just start again from scratch and build a pair of boards together.

Following on from BIG TORQUE the goal here is a powerful board for a big rider however this time i want more range, more reliability and more comfort. lots of failures last year due to water ingress and mechanical breakages limited my riding time so this build im going to spare no expense in making things robust and reliable.


12s4p SAMSUNG 30q
After spending a long time last year re purposing batteries we decided now was the time to start building our own packs so we split the cost of a tab welder and committed. We chose 30q because they seem to offer good range but also long life. 12s4p should be 12Ah or about 520Wh which is double the capacity of my old pack. for both boards that 100 cells :slight_smile:

DIY enclosures are hard . . . very hard. After building a few now i have mad respect for those on the forum that make awesome enclosures. I have learnt that if you want something reliable then just buy one of theirs cause it will save you a shit ton of time and cost down the line. We went with the @Kalyenclosures cause it looks great and was very well priced.

As a large guy i found that belts needed to be fairley tight to avoid skipping witch means that they didn’t last that long. After having a few snap whilst breaking I have been eyeing up some gear drives. Decided to go with @3DServisas Gear drives with the 5:1 reduction. The finish on these is great.

My old Trampa board is built like a tank but the street carve deck doesent fit the enclosure well and the mini spring trucks wont fit most gear drives so i decided to move to a full size ATB. I also decided to switch up from skate wheels to urban treads and also get bindings as i have eaten asphalt more than once due to cracks and bumps on local country roads. I went for the 6.5" urban treads to keep the top speed below 35mph and also to allow running at very high PSI when i need the range.

One of my old motors got knocked at some point and now resonates as certain frequencies. the Maytech motors having heavier than most however should be far more robust due to having sported motor bell at both ends. Might have to cut those long shafts down tho :frowning:

Last time I had a faulty battery i couldn’t work out why by board kept cutting out. i had no way of checking on the battery and no way of fault finding. This time a Bluetooth smart BMS will allow me to view the status of all cells in the battery. I also got a good case of face-pavement once because i hit the power and my BMS over-current decided to cut the power, after that i will only run BMS in bypass for discharge. This means i can get away with a smaller (20A) charge only BMS.

Since im bypassing the BMS for discharge i need a way to switch the board on and off. Decided to use the Unity as it has claimed higher output power than the old FOCBOX and also has integrated anti-spark power switch.


First job was to assemble the Samsung 30q cells into 4p groups. I glued the cells together with hot glue. To ensure good alignment the cells were placed in some makeshift cell holders.

Excess glue was “squeegeed” out with the corner of a credit card to ensure a clean join with plenty of surface area.

Cell positives were then fish papered to avoid any shorts.

Looking good :slight_smile:


I am using @Kaly CELL Fuse pcb kit to join cells in parallel and make it easier to join them into a pack. Additionally this kit means that every cell is individually fused adding another layer of protection in case of failure.

Nickel strips were soldered onto the pcb’s using a jig that held the strips in place, this means very uniform strip positions. large tabs are for battery negatives and thinner “fuse” strips are for positives.

PCB and cells then fit into an alignment JIG ready for tab welding.

At this point you could easily weld the cells by hand . . . but when there is this many cells to weld why do it manually?

After finishing enough cells for one board.

Second board done.


Cell groups have had large clear heat shrink tube applied over them to give another layer of insulation and protect them whilst being handled and moved around. clear heat shrink was then carefully cut off of the terminals in preparation for soldering once the pack has been glued.

The packs are very solid at the point, not really concerned about damage from vibration or flex.

We cut some wooden spacers to go between the cells to ensure that there was no rubbing between parallel groups and that everything fit snugly.

After some recommendations from work colleges we decided to use PURAFLEX 40, a “high modulus polyurethane sealant and adhesive” to glue the packs into place. We started by making sure the dividers were in securely.

Next we placed glue under the cell packs to ensure they stay in place.

The X shape is so that as you press the pack down all the air is pushed out and you don’t get left with bubbles underneath.

A final bead was then laid around the edge to make sure that cells stayed secure and help to stop any ingress that might occur.

2 glued up batteries ready for soldering.

I had my doubts about the PURAFLEX but it has actually worked our very well. After 48h to fully dry these packs are solid. I can hold one of these upside-down above my head and shake it vigorously without worrying that any damage will be done.

It also lasted much longer than we thought it would, we brought 3 tubes thinking we would need lots but we finished both boards and only used about half a tube.



Next job was to sort out the enclosure mounting hardware. The Kaly enclosures came with threaded inserts which needed to be drilled and tapped into the deck. Unfortunately i needed the pillar drill for this so had to do it at work (meaning no work in progress pictures).

In order to correctly position the Inserts we first clamped the enclosure to the deck in the correct position, making sure that no bolt holes overlapped the binding bolt positions. Due to variation in the binding positions on the 2 decks this means that enclosure position is slightly different on each board. Also worth double checking where the front of the enclosure is because they are not the same at both ends, make sure the binding bolts are in he correct positions before starting drilling.

We drilled through the enclosure mounting holes and into the deck with a pilot hole then removed the enclosure and drilled to the full width for the insert. The depth stop in the pillar drill was used to avoid drilling through the top surface of the deck.

Inserts were then wound in slowly with a hand drill whilst applying lots of downward pressure. This can be slow and frustrating but ensures that you don’t damage or strip any threads.

Finally both board have all mounting hardware fitted (and we were very itchy from all the fibres).


We decided to use copper braided cable to join the parallel groups together. The braid is 10mm wide and 1mm thick allowing it to have a lot of flex. It has 6mm2 cross section of copper and is rated to 63A. we decided to use 2 pieces of this smaller braid instead of 1 larger braid as after doing some tests we found that the thinner braid was easier to solder and remained more flexible for the same current rating.

The trick to getting the braid to remain flexible over short lengths is that you need to heat it quickly enough that you get a good joint but without allowing the heat to spread causing the braid to “wick” up the solder. This required us to source i larger soldering iron than i would usually use. luckily someone lent us an 80W iron without temperature control which would easily reach the required temperatures.

We also added an XT60 on the output ready for the Unity to connect to.


Balance cables and an XT30 have been added to the Battery. The balance cables are routed to the LLT smart BMS and the XT30 is to allow separate charging of the cells. This charge path will probably have an inline fuse added at some point.

Kapton tape is used to insulate all bare conductors on the battery and also keep balance cables from moving around.

As we have been building a board each they are slightly different but we are trying to keep the layouts as similar as possible.

Were still waiting on a Unity but everything seems to fit well.

BMS is up and running but initially seemed to be having troubles getting correct cell reading for the first 3 cells. eventually we found that this was because you must have the B- port connected in order to get correct reading for the first few cells. Now it looks good, all cells seem to be at a healthy storage charge :slight_smile:


As we needed a way to secure the Unity and BMS in place we decided to make a thin aluminium panel which they would both screw into.

We used aluminium as it should help sync some of the heat from the Unity during riding and the BMS during charging. Hopefully the large surface area will help some of the heat escape through the bottom of the enclosure easier.

Its not that fancy but it does the job. If i had access to a CNC that could cut aluminium i might have made something fancy but some times a hand made thing will do just fine.

This was the first time powering the unity off the battery but everything seems to be working so far :smile:


Next task was building the geardrives. First job is to mount the plate gears to the wheels. then mount the motor mount plates to the trucks. We can then check that the plates are parallel to the motor gears and lock tight them on.

Motors are then mounted and adjusted to ensure correct gear meshing.

Drive gear is unbolted from the wheel and placed into the drive. We filled them up with loads of grease, not sure how much you need but fuck it.

Outer case and steel plate are bolted on and the o-ring seal is fitted to keep all the grease in.

Wheels fitted back onto both sides (and also front truck)

Finally test fit them on the board :smile:

Rinse and repeat . . .


With both builds at the same point (-1 unity) attention turned to working out a solution to keep the motor cables tidy.

After having to do a lot of maintenance on my old build i knew that it would be usefull to be able to unplug the motors from the enclosure for servicing. But after spending some time looking for compact waterproof sensor connectors we weren’t able to find much that was suitable. We decided that a better solution would be to use the factory fitted connectors but try and protect these as much as possible.

I made a custom cable rise on my last board to keep things tidy and so designed a new riser that would house and protect both the motor connectors and sensor connectors.

The idea here being that this part fits on top of the trucks and all motor cables route through it. if protects the connectors and prevents accidental unplugging during riding.this is then sandwiched shut by the board when the truck is mounted. Fusion 360 model for this assembly can be found here

The part was printed from PLA at 50% infill and seems very rigid.

Connectors fit snugly into the recessed areas to avoid any damage that might be caused by vibration.

The plan here is that if additional waterproofing is needed this could also also be filled with some type of grease to form a grease box and prevent water ingress. i do have concerns that if water was to get to the sensor cables it could wick down the inside if the cable and get into the enclosures.


Next problem with the motor wires is finding a way to get them in and out of the enclosures in a watertight way.

We found that many cable glands avalable for <5mm cables (like 14AWG motor cables) were not designed to go through the thickness of the enclosure walls. additionally the sensor wire would likely be different thickness to the motor wires so it was difficult to find anything that matched in both sizes.

Eventually i decided it might be better to just design a custom cable gland that had the exact holes i need. CAD avalable here: should be easy to edit to fit your own cables.

The plan is that motor phase wires are on the outside and sensor wires are in the middle.

The outer part applies pressure to keep a silicone sheet sealed against the outside face of the enclosure. There are 4 bolts along the length which should mean that pressure is applied evenly and that there is a good seal down the whole length. The silicone seal has holes which are smaller than the cables ensuring a tight seal around each cable, even if the cable is slightly smaller than the enclosure hole. there is then a part that sits inside the enclosure which holds the mounting nuts and also ensure there is no sharp edges for the cables to rub on.

It was relativity easy to mount into the enclosure as i was able to use the outer part as a drilling guide for all the holes. First i drilled the outer 2 holes then fitted the nuts to hold it in place. I could then drill the rest of the holes without the guide moving allowing them to all be clean and accurate.

I then unbolted the outer plate, debured all the holes then reassembled the entire seal with the cables in place.

The end result is a professional looking part that should very waterproof. I purposefully chose a non-black silicone so that you can see the seal and to make this part more of a visual feature.

The custom seal and cable riser look great when fitted together. These motor wires should be the only visible external cables and should keep the board looking clean and professional.


Last job with the enclosure was to mount the the Unity switch and waterproof charge port. These were drilled into the side of the enclosure with the Unity switch in the middle of the rear segment and the charge port just behind. We had to drill these in quite a few size steps as the enclosure plastic seems to start to tear if you jump straight to a large drill size. Unfortunately there is no pictures of this process :frowning:

BMS and UNITY both got a good helping of thermal compound before being bolted down the their mounting plate, locktighting everything as I go. Mounting plate is then double sided into enclosure.

Cells are connected to unity and to BMS. Charge path from port to BMS then to cells is wired up.

15A fuse is also added to the charge circuit close to the battery in case of internal shorts or charger/BMS faults.

Motor phase cables and sensor cables are connected. Multiple Bluetooth dongles and remote receiver are installed and secured in place. system is power up and tested to check that everything is working :grin:

Enclosure is then taped around the perimeter ready for sealing.

Enclosure was then sealed, excess plastic was cut from the sealing sheet after mounting to ensure a good clean cut all the way round. Mounting holes were drilled in the sealing sheet to ensure that holes matched up with the holes in the enclosure.

FINALLY . . . everything was mounted to the deck :smile:


By chance I somehow managed to complete both my board and my house on the same day.

The kaly mounting hardware for the enclosure went on easily and looks sweet.

Everything is shiny and nice . . . Although im sure that wont last long.

Ground clearance is a little low, might have to change up to the larger wheel size if this becomes a problem. I guess for now i will just see how it goes.

The board looks awesome along side my friends boosted boards, they look like toys in comparison.

Cant wait to take it out for its first real test ride . . . . .


dope build. that was a very long post and can’t wait to see how it performs.


Attention to detail is astoundingly satisfying. Nice build(s)!


Yeah first one that liked your topic. I had already seen some off those picture. Nice to see this well explained build thread.


Great build! Also bec. you own the kaly enclosure how do you think it’s made? Vacuum forming or some other Method?

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Kaly enclose is available separately from his website.

The enclosure is defenatley vacuum formed. The finish is great and I think it’s well worth the price. Also comes with all the required mounting hardware :slight_smile:

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Stupid spell correct I know the kaly enclosure is available separately. The vac used must. be super strong in order to get the plastic to conform to such harsh corners.

i think he said he was waiting for another unity.

I am stocked how far attention to details can go… When the start of the production line? :rofl: This level of precision is unbelievable. Really well done


Awesome builds mate! Great write up too :+1:

Beautiful build bro

yes kaly has done an awesome job getting the tight corners well formed in such a thick material (~4mm). I tired to vacform my own enclosures before and even my best efforts resulted in slight webbing in the tight draws between cell groups as you can just about see below

When i received the enclosure i spend a while trying to work out how he did it and my best guess is that he uses a negative mold rather than a positive mold. Rather than sucking the enclosure over a bump and trying to draw the plastic down between the cells he draws the plastic down into 4 separate pockets. This means that the areas between cells are actually bumps and there is only 90 degree corners to draw into. Fucking smart . . . kinda pissed that i never thought of that back when i was trying.


My last board . . . . . .


Had custom milled electronics enclosure

And DIY vacuum formed battery packs

The problems . . .

First problem was that i used EPDM to seal the electronics enclosure. I dident know that the particular EPDM i had used was actually open cell EPDM. After getting caught in heavy rain on the way to work one day i lost one of my FOCBOX’s

I tried a few times to fix it but didn’t have much luck, seems like some of the traces were partially corroded and the FETS are a pain in the ass to swap.
But its ok, single drive was plenty powerfull to get me through the summer and I had a unity on pre-order so there wasn’t much point on wasting money on another focbox.

Second problem was that heavy riding and a bad plastic choice had caused the enclosure to begin to split around some of the bolt holes

Some temporary fixes meant that i could still ride it but i knew that the waterproofing had been compromised.

I rode it till the end but as the winter came i knew that it wouldn’t cope with the wet weather much longer.

When i got it back out in the spring to start riding again i found that it was already to late . . .

Must have got some water in the enclosure before i stopped riding it. the packs were built from 6x6s1p placed 3 in parallel then twice in series. This meant that the dead cell had killed a single cell in all 3 parallel packs, basically writing off 3 of the 6s1p packs (half of the battery’s) because single cells or parallel groups were not serviceable. Decided it was time to start again and do things properly.

When you live in UK, water is the hardest challenge.


Well at least you succeed in forming the enclosure. I am trying for the past 2 weeks with no success. I now think the problem is my suction so I am getting a stronger shopvac.

Here my second best attempt so far (still ugly AF) and I had to finished a bit by hand.



Honestly if i was ever to make more of these there are quite a few things that would need to change in order to make production cost effective.

With the battery i tried to copy kaly’s builds as close as we could work out from pictures and videos. But tbh building the packs takes a significant amount of time. First you need to attach the strips to the PCB, even with a jig this takes time. As best i can tell kaly spot welds these but we soldered them as i dont mind to spend the extra time to know im not going to die.

Then we automated the spot welding to save some time but even just swapping the packs into the machine and monitoring it took quite a while. Kaly is welding these by hand for every board so it must take him even longer.

Additionally you then need to solder the flexible braid onto each individual parallel pack. This is difficult due to the heat needed and there are 4 of these joints on most parallel groups so 44 joints total per finished board. Building 2 of these was enough for me.

If i was to make more boards i would be having packs welded into 4p groups by another company like on the new evolve boards then having a single pcb per 4s4p group. fewer longer pieces of larger braid would mean that only 6 braid solder joints would be needed for the whole pack and added length would negate the problems with solder wicking.

Furthermore there is a lot of loose wiring in the enclosures that is both a point of failure and time consuming to make. I would probably try to reduce all of this as much as possible using PCB’s for wire routing.

The other job that would be shit to do on mass is drilling and screwing in the mounting hardware, but im sure kaly must have jigs for this.

Building boards like this its a lot of work and if your buying all the components from other vendors there is not much profit margin to be made. Fair play to kaly for making it work, i dont know how he was making much of a profit on his earlier boards. The smart move here is to start building more and more yourself because this way you make profit on each component as well as on the assembly. I guess this is why kaly has moved to using his own deck, trucks, wheels and gear drives. lacroix seems to be doing the same. I got a lot of respect for both these guys.

Side Note :
I would love to see whats going on inside the XL50 modular 12s3p packs. Is kaly using his own BMS?


I agree on what you said. What most of the people do not get when calculate the cost of something is time spent. Easier to calculate only parts cost but actually is the building time that makes everything worth the money.

PS: your spot welder is amazing btw

No idea about the BMS.

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Really beautiful work mate, very, very detailed & thoughtful workmanship

Will have to steal some of your methodology


On this point, I got stranded at work today.

Still not brave enough to ride it in this weather after losing my last board to water damage . . . Twice.


Amazing build love it !
Nice rig you did with the spot welder !
Would go quickly with bigger wheels, it’s very low especially if you wanna go off road

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i’d crap my pants and roll over if my board went over that big of a puddle.