Although I am new to the world of electronic skateboards, I have done a lot of reading and watched hours of YT clips. Joining this forum was a massive step in the right direction with so many very knowledgeable people who seem more than happy to give advice. When I first began thinking of building my own board, my initial ideas are far different to where I am now (thanks mainly to this forum) and I am just about to hit the ‘BUY NOW’ button on a few items to get me started. I figured I would throw up my ideas here and try to open a discussion on whether this is the ‘right’ choice or whether there are alternatives that I haven’t yet considered.
Firstly, the environment that I will be riding is not your ‘standard’ urban environment. I live in a very remote part of Australia (Arnhemland) and there are no real ‘roads’ up here. Most of the surfaces are either just dirt tracks (gravel, dirt, sand (not too deep), etc). This led me to the idea of building a Mountainboard with tyres (tires) that would be suitable to the area I want to ride. I also wanted a board that will be easy to turn as most of the tracks can be pretty tight. I am not aiming to build a board with crazy fast speed, and I would rather compromise speed for torque and longer battery life.
So, with all of this in mind, here is what I have so far as my ‘parts list’.
**Trampa Urban Carver board with the Vertigo trucks and 7" wheels (this is put together as a package from Trampa)
**E-Toxx Mini Direct Drive drivetrain. I have chosen this as it is a ‘sealed’ unit and I think will be better suited to my environment in comparison to a belt drive option.
**2 Dark Matter motors 6374 190Kv
**Dual Focbox
**Enertion Nano-X controller
These parts have all been ordered and I am awaiting their arrival.
Apart from the above, I am still undecided on a few other items like the battery, battery tray and BMS. In my ideal world, I would want the batteries situated under the deck and I have seen some awesome custom builds with low profile, flexible battery trays (like the one on the build that whitepony did), but I can’t seem to find anything like this available to purchase. I’m also undecided on battery choice at the moment. I do know that I want 10s4p, but not sure whether I go with LiPo or Li-ion. I’m also on the fence in regards to a BMS and have read that some people don’t use them where others do.
Anyway, that’s about it for now. Keen to get some feedback on the above and can’t wait to get this built and start riding.
Regarding the batteries would look at what range you want to get then use some of the calculators to get a rough idea of what size in terms of Wh you need. 10S with 190kv should be good (10*4.2V*190kv = 7980 rpm, 60000 erpm /7 pole pairs = 8,571motor rpm so you’re under that limit which is good for the DRV safety on the VESC4 based hardware).
In very rough terms 10Wh = 1km so if you want to go 30km between charges you need 30*10=300Wh. Most 18650 cells are in the 2500-3000mAh or 2.5-3Ah range and at 10S nominal voltage being 3.7V you have about 3Ah*3.7V= 11.1Wh per cell, so can take your total Wh you want for range divide by 11.1 and get the number of cells you need in total to be carrying that much energy. If you go with lipo can just take the Ah on the battery and multiply by 3.7V*number of cells and get the total Wh. Example 10S 5Ah (5x2S 5Ah linked in series) then you have 10S*3.7V*5Ah = 185Wh
I’m one of the anti-BMS people but I mostly worry about people buying cheap ones with bad instructions and wiring things wrong… also you’re effectively strapping your charge circuitry to your board which is basically like a vibration test table. Basic engineering stuff, less parts = less parts breaking.
That said if you go 18650 and are spot welding your own pack together etc. then I don’t see it as a lot more effort to also put a BMS on there for easy charging.
Wow - some great info/advice there - thank you very much.
One reason I am leaning more towards LiPo is that I have experience with this chemistry (flying UAV’s) and I have all the charge gear.
When it comes to the 18650 batteries, one big hurdle is that I don’t have a spot welder and don’t really want to fork out for something that I may only use once. I know that I can purchase these battery packs already made up, which is something I am considering.
Decisions, decisions…
No problem fixed the * in my post apparently need to escape them now with \
Also on the batteries the 3 or 4P is usually used on 18650 based ones because the max discharge/IR on the cells is such that you can’t pull 40A+ from a single cell (usually more like 15-20A per cell), and the more you distribute that amp draw across cells the better (putting them in parallel does this).
With LiPo you have to just look around to see what’s good, there is a C rating on the batteries for calculating max draw do C rating * Ah capacity = max discharge in amps, example 40C*5Ah = 200A the higher that max discharge the better you want it to be well above whatever you will ever actually draw when driving the motor(s) (also manufacturer C rating can’t always be trusted). I also had a charger and some experience with them and also no spot welder or experience with that so stuck with LiPo.
I got 10 miles plus with 5ah 12s 25C Lipos without regen braking
with 7.4ah 12s 90C I would expect to get 15 miles plus
Matter fact with my 5ah 10s 60C Lipos I have gotten up to 14 miles on flat ground.
So, just to ensure I am on the right track here, if I go with the above packs for my battery power, then, do I need a BMS? For charging, I am happy to just remove the packs to charge them. Just need a way of being able to easily split the packs to balance charge them individually.
Well the choice is either BMS and you don’t have to take them out, simple connection for charging/more portable charger or no BMS and using a balance charger
Either works
Okay, I’m in a bit of a bind here, regarding batteries and charging. For batteries, I only want to have a 10s setup. I reckon I’d put myself in hospital with 12s, especially after watching some of the YT videos with 12s boards - that’s some crazy shit right there.
So, if I settle on 10s LiPo, then I am best to get 5 X 2s packs. Obviously, the higher the C rating, the better. This leaves me with two possible choices, so far.
This one:https://www.smc-racing.net/index.php?route=product/product&path=67_152&product_id=126
At this stage, I am leaning towards the Revolectrix battery as I know and trust their stuff after using it for many years flying UAV’s.
That aside, then I am left with a decision on BMS. This is all new to me, and there is a lot of info on this forum about BMS, but my brain is in overload with all the info I have taken on board so far. Not even beer is helping!!!
So, if you were to recommend a BMS for my current setup, what would it be and why?
If going BMS there’s another decision to be made, use the BMS for charge and discharge or just charge, I recommend charge only BMS and let the vesc handle limiting. Either the Bestech D140 or D190 are good charge only BMS, the 140 does 10A, 190 does 15A
Yep the Focbox, or VESC in general, have settings to limit the discharge of your battery. You can also limit the amps sent to the motor.
And you can even set a voltage limit for the battery, so you don’t discharge it too much.
Very intelligent those things, when programmed properly !
Not sure if this is already available, but if not, why isn’t there a system that incorporates something like the Focbox/VESC6 (or whatever) with the BMS? Surely there is a market for an item like this??
44.4v*7.4ah= 328.56Wh÷20=16.428km/10.2m