Prototype technical details to start:
13s4p battery pack with LG HD4 cells, 54.6 V max, 48 V nominal, 100 amps continuous output.
Battery is split into four separate 99 Wh 13s1p packs for air travel compatibility.
Enertion FOCBOX upgraded with 12 gauge phase wires and an XT90 connector.
Torqueboards 6380 170 kV motor running at 85 amps, 4000 watts at 48 V nominal voltage.
9T hardened steel pinion driving 70T steel sprocket with #25H chain.
4" scooter hubs with 10.3" diameter Kenda K671F 3.00-4 DOT-approved pneumatic scooter tires.
Steering arms are 3D-printed stainless steel (gold-plated of course).
Frame rails are 6061-T6 aluminum.
Deck is 3/16" polycarbonate.
Each pack has an XT30 connector and a JST 14-pin connector. The four packs plug into 4-into-1 power wiring (16 gauge XT30 to 10 gauge XT90) and a PCB with four 14-pin JST sockets, running into a single BMS. The BMS is only on the charge side, the FOCBOX controls current on the power side.
13S? is this a standard or modded FOCBOX? The transients from using DirectFETs are almost certainly going to kill the mosfet gate driver at those voltages.
Just curious, why chain and not synchronous timing belt? Nevermind, just realized it was because of the gearing ratio.
Awesome looking board you’ve put together here. Hope you’re successful.
Am curious how or if you’re pushing 85A through the focbox? I assume that’s battery amps since you note your battery is built to push 100, but maybe it’s not.
How much more power do you think the board could practically make use of?
I haven’t had issues with the antispark yet, but I’m aware people have problems with them. Would love to have a single-channel VESC with antispark built in, but that doesn’t seem to exist yet.
This is a prototype so I take it apart and fiddle with things often, but the production model will have everything properly secured, and the wiring harness will be cleaned up and optimized. This was a case of “it works, ima go ride now”. I did tape the phase wires. Nothing else has even loosened up, most likely because it’s all really crammed into the enclosure.
I’ll be developing hooks, straps & bindings for the production boards, just haven’t had a chance yet for the prototype.
I hope to develop an app, prob working with an existing app creator to customize for the speedboard, with alerts like “check your chain tension” and other inspection & maintenance.
The cells have been amazing. At 25 amps continuous they barely get warm. The objective was to create the highest output board in the lightest package. I plan on having an extended range pack available as well.
I appreciate all the questions!! I’ve learned a ton working on this, but I still have so much more to learn.
13s only gets to 54.6 V and the FOCBOX is good to 60 V. I ran the original prototype at 14s and never had a problem with the FOCBOX besides cutting out when braking at 100% charge. This has been completely solved by dropping down to 13s.
The gear reduction is a big part of why I use a chain, but the main reason is I’m only driving the one wheel, so I need something that absolutely will not break. The #25H chain has a tensile strength of 1300 lbs.
Yes, the single BMS is running all four packs in parallel. An added bonus is the four packs are wired together through all their BMS leads to keep them more properly balanced if you don’t charge to 100% often to let the BMS balance the cells.
I’m running 85 motor amps. The FOCBOX is bolted onto a heat sink at the bottom of the board, so I’ve been able to successfully run it above its continuous rating. Battery amps are set at 100.
While the MOSFETs and the gate driver are rated for 60V (with the drv having an absolute maximum of 65V), This does not mean that they are intended to be operated all the way up to that maximum rating. Transients will repeatedly exceed those voltages and wreak havoc with the electronics.
I am very surprised you did not encounter a blown FOCBOX during testing. Are you running it on BLDC or FOC?
If you are okay with BLDC, I can design an ESC with integrated antispark.
Actually, forget the antispark, just give it a low power sleep mode.
Thank you! Honestly I think it’s safer than a four-wheel board, it’s literally impossible to get speed wobbles, and those 10" tires roll over anything. I hit a 1.5" palm branch two years ago at 25 mph while I wasn’t paying attention, made a loud noise and scared the shit out of me but the board wasn’t even phased.
Yep I’ve blown a focbox @ like 55 amps albeit it had the standard heatsink and no more. And I did throttle it at a stop when it blew so not the best conditions for it.
Would feel more comfortable with vesc6 or something newer than 4.12 hardware, but I’m no esc designer so I don’t know a whole lot about 'em to have good advice.
Another reason I used the LG HD4 2100 mAh cells was to keep each 13s1p pack to 99 Wh so you can remove the four packs, check the board, and carry the packs on the plane. I may have an option to upgrade to a higher capacity non-TSA/FAA-approved pack setup, but I’d rather have an auxiliary 13s2p pack that’s as close to 160 Wh per 13s string that bolts onto the deck.
I ran my first prototype at 14s for a year and never had a problem with it, as long as I avoid braking immediately after charging. I’ve been running this prototype at 13s with zero issues, including racing at the Streets of Lancaster GP running 120 motor amps. 100% acceleration and 100% braking over multiple laps, and not a single issue from the FOCBOX. I’m running it in FOC.
