Mac 6T 20" wheel, 40 amp controller.. good idea?

-Mac 6T 20" wheel from em3ev
-S12SN 40 amp controller from bmsb
-lcd3 from bmsb
-48v20ah high C, 50a continuous from bmsb

Great idea, or terrible mistake?

Wheel link: http://em3ev.com/store/index.php?route=product/product&path=36&product_id=107
Controller link: https://bmsbattery.com/ebike-kit/72...r-ebike-kit.html?search_query=s12sn&results=2
Lcd3 link: https://bmsbattery.com/ebike-kit/67...s-ebike-kit.html?search_query=lcd3&results=32
Battery link: https://bmsbattery.com/ebike-batter...battery-heat-shrink-battery-pack-battery.html


My goal is to build a 20" folding monster, for cocking about and the occasional commute to some properties around the city.

I love biking and for me I get excited when I see a hill, and I usually ride 9 speeds in the rear on a trek aluminum frame 700c (Trek 9th District from a few years back), but I intend on having this (my first ebike) on a 1 speed folding bike with horizontal dropout, and 20" wheels, and pretty much never pedal.

I want it to pull hard off the line, and to hit its top speed of hopefully 30+mph asap.
I understand that the 6T has less pull, but I saw all this talk in reference to people who were using it on 26" wheels and 700c, whereas I'll be using a 20".
Is the 6T an ideal motor for a 20" performance machine?

I'm planning on running it with a 40 amp controller, and using the lcd3 to limit amps and work my way up to something comfy.

If I limit it's amps, as well as limiting it's speed for a less rushed commute, will it be more wasteful at the same limited speed than say a 8T?

Essentially, I'm not trying to run it on max at all times, but instead to choose a normal cruising speed and amperage, but be able to kick it up to max with the lcd3

I've tried using the tools at bike.ca, and just don't know how to process that info.

I figured you folks can help, and after searching for days for the answer, I figured I'd just ask it outright.

Also, I've seen people talked out of using the 6T on the forums, but for larger wheeled applications.
Furthermore, Paul from EM3ev said it was a "difficult motor to drive" and I'm wondering, in what way he means. (asked and am waiting for a reply)

Lastly, referencing the above linked S12SN controller, will it handle this duty well, or will I end up frying it somehow?


Thanks so much in advance guys!

-AL

Welcome, RAT TAT TAT

Please fill in your location
https://endless-sphere.com/forums/viewtopic.php?f=3&t=66302

You are in the right place to ask questions.

Thanks for the welcome and suggestion markz.

I rode a http://www.ebikekit.com kit, and thought it was great.
Being born and raised in America, I figured why not see how far I can push a geared motor, instead of getting what I know works well haha.

Bike I rode was:
-Dahon Mariner 20" folding bike
-Ebikekit.com 500w rear geared motor (similar to Mac 10T I hear)
-Ebikekit.com 22 amp controller (square wave?)
-Bmsb 48V20ah, 50a continuous

Yes I was similar, I rode a BionX at a local bike store, but it was limited to 32km/h by law, and it wasnt THAT impressive, but I liked the fact it was a bicycle powered by a electric motor, rather then a noisy gas engine. I was totally turned off by the fact the BionX bike was like $2500+. Anyway I am not a "guru", I am a newbie aka n00b....my thoughts are you should go to a smaller Tooth count, like a 5T or 4T to get your KV or rpm per volt up higher, because you have a 20" wheel. I dont bother trying to figure out the formula for speed, I just use ebikes.ca motor simulator because my motor is on there. I doubt the MAC is on there. So some other people with more experience can chime in on that.

Think of your desired speed, and if 20" wheel is set and given, then buy an appropriate tooth count motor for your desired speed.

I do believe the "T" refers to the number of turns of wire on each bit of the inside (stator).

So because there are only 6 winds, it is a thicker gauge copper wire.
Which I learned from doing some reading up here on the forums.
Was able to get some info, but wanted real world experience from 20"ers if they were out there.

Thanks again for your input!

That set up will do everything you want. Similar setup on my old bike would lift the front wheel about four inches at the start if I didn't lean forward. I was getting 33-35mph on flat ground. If your going for a folder though, the Jetstream would be a better/safer option at those speeds. The guy who bought my bike died riding it. The cop on the scene said there was nothing wrong with the bike, but I never got to see it after the accident. There's still that little voice at the back of my brain that would like to know for sure.

Well, even in a 26" wheel a 6t will perk way up on 2000w, vs 1000w. In 20" wheel, it will run real nice even on 1000w.

Some will say, that type motor might be better off limited to 1500w. But again, that might mostly apply to 26". In 20, it will reach it's peak rpm much faster, with much less wasted energy into heat in the first 5 feet.

So in 20",, I'd say go for it. Or certainly go for it at 30 amps for sure!

The battery,,,, I tend to say "cut all claims for continuous discharge in half" Not that the batt wont' do it, but because the batt usually lasts a lot longer if you never cruise at more than half the stated c rate.

Half of 50 amps though, is 25 amps. Plenty for cruising 30 mph easy. So just look at voltage sag under load when you get it. Anything less than 5v sag leaving a stop sign would be generally ok. If no way to measure sag, look at how hot the thing gets. If it gets hard to hold it after a ride, definitely back off amps some.

worldpax,
This sounds terrible. However that's kind of what I wanted to hear.. no so much the dying part.
I would like to do the jet stream, just out of my bracket right this second. It would all be swappable though if I decide to go that route.

Now if I limit this thing with the controller to say, 25amps and limit top speed to 27, will the thing run efficiently, or will it be running the wheel to low?

How were the hills with that rig you had?
Thank you so much for your input!

dogman dan,
Dan! thanks for making me join the forum! Totally helped me out, and really made me understand this stuff.
How do you feel about occasional hills? will anything above 10% grade kill this thing?

Just an fyi, I laced a similar geared front motor into a 26" (ran ok), then a 700C ( big step in the wrong direction), then a 24" and a 20". It got happier and happier every step down in size.

Oh my lord, you guys are getting me hyped! It's all ordered except for the bike now.

Gonna still figure out which 20" frame?

maybe a bmx with front pegs so i can sit back and steer with my feet hahah!

but seriously, if I find money on the street, I'm going the jet stream route.
otherwise, steel framed Dahon Speed Uno

Make sure the tires are up to snuff. I was always fearful of a blowout and checked my pressures religiously.

Thanks for coming through with the information.

I'll try and post pics when the gear gets in, and maybe even some build details for those trying to do the same.

I capped my 10T at 1500 watts and it will only go over 1000 watts if I am climbing.

I went up a 13% grade with 26 inch wheels and 205lbs total weight at 17 mph. At the top of the hill, the motor was at 71C. If the motor were to hit 100C, the CA would scale back the power anyway.

A motor with fewer winds with automatically draw more watts when meeting resistance. For this reason, I would not consider a 6T unless I were willing to cap it at 2000 watts - which should be ok as the CA will scale the power back if it gets too hot.

A 10T on a 26 inch wheel would be like a 7.3T on a 20 inch wheel. I am running 30 amps. So I think a 6T for you with 40 amps sounds good. I think you will get 32 mph.

Thank you for the input rsilvers.

Update!: It seems I caught a local craigslist 30 minutes after it was posted, for a Dahon Jet Stream from 2010 for a pretty decent deal.
About as much for a Dahon Speed Uno brand new. Something in the cosmos has aligned and this seems to be coming together nicely.

Something in the cosmos

Click to expand...

Blame it on the aliens RAT TAT TAT.
Especially this guy Giorgio A. Tsoukalos
https://en.wikipedia.org/wiki/Giorgio_A._Tsoukalos#/media/File:Tsoukalos_NOLA_Comic_Con_2012_A.JPG

Got a Great deal! $400 for a fully functional one. A rusty bolt here and there, but for the same price as an entry level Dahon, worked out lovely!

Torque arms a Must. Before it's to late. Thought about a 8t rear ? It might make Paul happier.

That's for sure!

Why is it that he would be unhappy?

An 8T with 20 inch wheels will probably go 26+ mph. If that is fast enough, then it will have more torque and not slow down as much going up hills.

That is the speed I get, except with 40 amps there will be more torque than my 10T with 26 inch wheels as I have 30 amps.

On the one hand, I like my speed and going faster wastes power (speed kills range). On the other hand, when the speed limit is 30, I can't own the lane, as cars want to go 35. If he had a 6T, he would be able to own lanes on many roads.

If his batteries can really handle 40 amps, then I would probably lean toward the 6T. If his batteries cannot handle 40 amps, then the 8T.

Also factor in weight - my bike and I come to 205 lbs. If his payload is much more than that, that is an argument for an 8T so that it can still climb.

I ride a 20 inch folder with a 10T BPM and 20S battery + 20A 6x4110 fet controller, which is similar to a 6T MAC with 12-13S (48V) battery. The bike does about 30-33mph and climbs with ease.
HOWEVER, the rear positioned motor and battery make the bike severely unbalanced. It is quite unpleasant and dangerous on takeoffs, even at 20A it wants to lift the front off the ground if I don't lean forward, and there is generally low front wheel traction. I haven't crashed this bike yet, but had some close calls. All of this is made worse by the fact that is is a production push bike with short chainstays. Had it been made with longer ones, like most e-folders that need to accomodate a battery, I could get away with 25A (equivalent to 48V40A @ 6T) for even better take off, and have a safer, more stable ride in general due to increased wheelbase. As it is now, the bike is quite scary. Therefore I strongly recommend getting a used e-folder with extended stays and give it a new motor+battery.
I had the same motor in a 700c wheel and while it had less torque, it was a safer ride, less noisy AND more efficient at moderate speeds due to less non-copper motor losses. To lower the noise, I suggest a sine wave controller.

I have an Infineon controller, which is square wave. While I am not sure what a sine-wave controller would sound like on my bike, my noise seems low. I can ride by someone and I don't think they can hear the motor. I have passed several spandex-wearing bikers and they probably only know it is an eBike from the large visible battery and hub. I think I would enjoy a Q100H motored bike with a smaller battery since I am trying to pedal most of the time. A true 500Wh pack would have suited my Pedlec needs.

rsilvers said:

I have an Infineon controller, which is square wave. While I am not sure what a sine-wave controller would sound like on my bike, my noise seems low. I can ride by someone and I don't think they can hear the motor. I have passed several spandex-wearing bikers and they probably only know it is an eBike from the large visible battery and hub. I think I would enjoy a Q100H motored bike with a smaller battery since I am trying to pedal most of the time. A true 500Wh pack would have suited my Pedlec needs.

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Mate, the thing is, you run a 26" wheel.
When run in 20", the gears will turn 30% faster for the same speed, and they will transfer 30% less torque, so in total, the gear teeth will push about half the force compared to 26", so they will get "looser" and thus noisier. This is my experience, but frame resonance may also play part in total noise factor.

Mine is on Titanium. Maybe carbon is the loudest.

Most noise I hear is from the square wave controller. The 9c whine. A sine wave controller is much quieter.

Very excited!
Ordered some Shinko SR714's (16x2.25)

Having some faith that I can get these to work, as they would be ideal for the higher speeds and I can worry less about a flat..