Just before this I’d finished up with my 2WD 6374 12S4P P42A build and decided it
had more than enough power and was pretty heavy. At the same time I started hitting up the skatepark with a buddy and I decided I wanted an electric skateboard that had enough power to pull me up the halfpipes, was as light as possible, and had a swappable battery so I could take it on longer journeys if I wanted. I went with 12S because I had a 12S 4.5A charger already for my other board so I wanted to reuse that. Also I’ve never seen a 12S1P before and I knew it could be done with the power that the P42A can put out.
The Battery:
Cell: Molicel P42A 21700
Config: 12S1P (running at 40A discharge and 8.4A charge)
Swappable in a 3D printed enclosure (latches in by slots in the battery enclosure together with the XT60 port on one side and 2 M5 bolts on the other side). Each battery pack has it’s own charge port so I can charge one while riding the other.
Charger: 4.5A. This is just over the rated charge for the P42A cells, meaning I’m fastcharging them, but I’ve been monitoring it every time I charge it just to make sure it’s not getting too hot. So far it never goes above 33 degrees C. It takes just under an hour to charge a pack.
BMS: LLT Power 12S 60A smart BMS running unbypassed. I’m only going to use this BMS from now on because I love how configurable they are. It’s Bluetooth, so I can monitor the voltages of the cells at any time, and it has two thermistors that I use to measure the temperature of the cells and the BMS itself during charging.
Nickel and Wiring: 15mm wide 0.2mm thick pure nickel from nkon and 12 AWG wire. Though this is probably underspec’d I figure I don’t pull enough power to cause any issues.
Motors: 2x FS 5055 200KV 1380W. These are made to fit Evolve mounts. I wanted the smallest motors I could find and these did the trick.
Gearing: 36T / 15T with an idler pulley. Idler was used because I can’t adjust the position of the motors at all because the motors are meant for evolve mounts, where I’m using torqueboard mounts. Also, idlers are sick. I never have to worry about the belt skipping.
Wheels: Discontinued Otang Balut 72.5mm flywheels. A friend gave these to me forever ago and I had recently found out that they perfectly fit the 36T torqueboard abec clone pulleys when I use 3 out of 6 of the bolts and a couple 3D printed spacers. They’re small and light and pretty soft. They’re a bit too small for high speeds, but they’re perfect for the skatepark. I may switch to 83mm at some point though just so I don’t have to avoid every pebble on the road.
Trucks: Caliber clones I had lying around.
Deck: Landyachtz Schooner Swell. I was going to go with the Dinghy but I thought I’d need a longer wheelbase because I originally wanted to make a 12S2P flatpack, but I ended up not having enough space in the end. https://landyachtz.com/product/schooner-swell/
Electronics:
VESC: 2x FS mini FSESC 4.20 50A. They were cheap and small, and although I’ve had problems with FS in the past I’ve had no issues at all with these, other than the fact that they run a bit warm when only at 20 battery amps per motor.
Anti-spark: FS 200A smart switch. It was small and a friend of mine had it lying around so I bought it off of him. It’s got some cool features though: push-to-start and auto shut-off. I basically never touch the button and just start riding, waiting for it to connect to the remote.
Remote: VX1. Bought it for cheap off a guy I in my esk8 group when he had problems with it disconnecting constantly. I’ve had no problems since I soldered a copper plate to the antenna in the transmitter.
General specs:
Battery Capacity: 172 Wh
Range: 10-16 km. Usually closer to 10 with how I ride it
Weight: 13.6 lbs
Top Speed: The fastest I’ve gone is 40 kmh but only on the smoothest of roads. The thing sketches me out going that fast because of the tiny wheels and short wheelbase.
All in all I’m really happy with it. It has plenty of torque. Probably too much for such a small board with a kicktail. I find I go into a manual quite often when I accelerate too hard. Surprisingly there is little sag though, probably because I set my cut-off voltage down to 2.7V per cell.
I’ve taken it to the skatepark and I’ve been loving how it performs. I purely ride bowls and halfpipes and this board has enough clearance to get over the lips of the ramps and most other things. I don’t street skate, so I don’t do any tricks on it, but I let my friend borrow it and got him to ollie it at the park. I’ll attach the video below. Next I have to get him to kickflip it.
The only problem I have with it is the braking, which is pretty lacking at high speeds since I’m only running 8.4A regen and have such tiny motors.
ive always wondered how to make a good interlocking enclosure and you nailed it! nice job!
each battery has its own bms i assume?
regen isn’t the brakes, if you want more brakes you need to use << motor current max brake>> and set it to a bit less or the same as the << motor current max >>.
i run 95/-75 on my big setup. you could try 40/-40
I run my max motor current at 35A and my motor max brake -35A, and my braking is great at low speeds but once I go over like 20 kmh my braking power drops off. As far as I understand it, very little current goes back to the battery at low speeds, and the braking is mainly just heating up the motor, which explains why I have good brakes at low speed. I think at high speed is when current goes back to the battery, and my regen current is low, so I max out the braking quite easily at high speeds.
I may be completely wrong in my thinking though. If so let me know.
I may just increase the regen past the rated max charge for the P42A (maybe 10 or 12A) and hope for the best. I’ve seen people do that with 30Qs so I’m hoping that’s okay if I’m careful.
The interlocking enclosure isn’t perfect. I definitely need to redesign the VESC enclosure to support the battery better. I thought I designed it well enough, but I’ve noticed some cracking near the bolts. I superglued it and it’s been fine since, but ideally it’ll need to replaced so it can better support most of the entire weight of the battery.
Also yeah each battery pack will have it’s own smart BMS. I only have one battery right now though. I’m waiting on the second BMS to arrive before I build the second.
I love the interlocking enclosures! Have you considered making a 12s2p pack? It might be a tight fit, but I think you could do it. Either way, great build!
i know @MysticalDork or @b264 can explain the details much better than me, but regen has nothing to do with braking, it’s only purpose is to use the energie created to charge the battery ( albeit not very much with our real world testing).
you could set regen to 0 and it wouldn’t change anything.
Do you know how your bms is setup? whether it’s bypassed for the discharge or not?
so since it is 60a then you can easily increase the max braking. having your brakes stronger than your accerleration is no issue so you could do 35/-45 if you wanted
edit/ so you only run at 12s1p at a time?
because then i understand why you are at 35a that’s your max battery A.
That was the plan originally! I tried to get it to fit but I decided that it couldn’t be done with a 3d printed enclosure. 12 cells long is more than the build height of my printer (250mm), so I would’ve had to break the enclosure into modules or made one long enclosure that was using a few connecting 3d printed parts, which I thought would be a bit flimsy.
Then I thought about making a swappable battery which imo is the best solution, because if I want I find the time to make the second battery pack I can carry a 12S2P around with me.
Actually i’m doubting myself a bit now, i’ve never seen a scenario where the motor current max brakes is higher than the battery max discharge. I’ll wait until someone else chimes in @b264@MysticalDork
As an update I just tried with 0A regen and I have zero brakes The motor just jitters when I hit the brakes.
Increasing the motor current did help though at least at low speeds. I’m only testing inside though because it’s a bit snowy outside so I can’t tell you if it’s any better at speed.
Our motors and ESCs only work so well as space heaters. Increasing the amps going back into the battery will give you better braking at high speeds, where regen IS the bottleneck.
@BrassMittens unfortunately your battery pack is quite small, so you’ll be ruining your cell life with high regen, but it’s your only option. 10-12A is definitely safe, and I would even set it to 20A for emergencies, but keep the limit in mind when braking normally.
Edit: I see your BMS isn’t bypassed, so make sure not to fry it / trigger its cutoff. I don’t know that model’s specs off the top of my head, but usually there’s a limit of 20A, so something like 18A would be safest.
Fair enough. The regen energy has to go somewhere I suppose.
@BrassMittens unfortunately your battery pack is quite small, so you’ll be ruining your cell life with high regen, but it’s your only option. 10-12A is definitely safe, and I would even set it to 20A for emergencies, but keep the limit in mind when braking normally.
I’m already running the cells at 40A discharge so I’m not too worried about the cycle life as it is haha. I’ll bring it up to 12A for emergencies. I rarely go very fast on this board anyway so in an emergency I’d probably just run it off.
I’ve gotten it to cutoff discharge due to undervoltage (I forgot to set the BMS cut-off to 2.7V from 3V) and overvoltage, but never for overcharge or overdischarge. The BMS is rated for 60A in and out though, so I assume it will be fine, but I’ll definitely give that a test.
Man I love this build this idea is insane being able to quickly switch batteries plus you pulled it off really nicely
How long would it take to change batteries and how many spare do you have?
Taking under an hour to charge a pack means you’re decreasing longevity a little bit. For maximum pack lifetime maybe get another charger. Of course, it’s a swappable battery, so… yeah. Might be fine
that’s your max battery A.
The motor just jitters when I hit the brakes.