Newbie Here, Saying Hello - dual motor build planning

[Mikebergy]

Hi ES,
This is a wonderful place, with a LOT more smart people than I am used to seeing on an online forum (cannot even approach the knowledge base that is Lebowski and Liveforphysics). Anyway, I begin my journey here.

My plan is a 1000W, dual motor single speed for getting around town, and learning how to outfit a bike cleanly. Here are what I am looking at building with:
Bike - Raleigh Tripper SS with disc brakes
Motors - matched Q128 on 700c wheels (28-35c tires)
Controllers - Infineon 6FET 3077
Battery - 4x 6s5200 HK Multistar lipos in 2s2p with BMS board. Need suggestion on BMS
Charger - reliable bulk charger (suggestion)
Need advice on monitoring- CA? Will that work with dual motors?
Also could use advice on reliable wire routing and good looking, simple connectors. I'd love to have hermetically sealed Milspec type connectors but that is not likely as they are pretty expensive. Anybody have a good waterproof clip-type power connector for battery and controller connections?
I need help figuring out what windings on the motor I should be looking to get - looking to cruises @ 25mph around town. Since the load will be distributed, the motors could be a hotter wind and not suffer too much. Are these Q motors decent to rewind if needed? I have experience reminding RC bell motors but these are much bigger, and I am curious how much of a nightmare they are to dismantle. We have hills here, but I am not really looking to go conquer them with this - that is what my legs and my regular carbon road bike is for . Thanks for any advice, where to get good deals on hardware, etc, I appreciate it. - Michael

 

[amberwolf]

Regarding CA with 2WD, and waterproofing/etc, there are some threads about that in the stickies here:
https://endless-sphere.com/forums/viewforum.php?f=21
for ebike general and ebike technical.

 

[dogman dan]

Re connectors, many kits out there now have decent water resistant connectors. Just don't buy a kit with crappy scooter style molexes. Hunt around, and there are kits out there with nice looking controllers and tight plugs.

I don't know how to run a DP CA on two controllers. But a stand alone CA will work fine on the wire from the battery, between the battery and the Y connector to the two controllers.

Assuming 12s, 44v, you will need a faster winding for 25 mph. Something in the 375 rpm (at 36v) ballpark.

For bulk charging Lipo, my favorite charger is the one from EM3ev. It has a three position switch for half charge, 90% and 100%. Most of the time I never need more than 90% to get around, so I have less risk of an overcharged cell.

You will definitely want at least one cellog 8 for checking voltages, and if you do need 100% of the capacity, then you want low voltage alarms you can set to the volts you want to stop.

AS ALWAYS, never store or charge your lipos in a place you would not build a fire.

 

[motomech]

I'm not particularly smart, but I have been doing what you are talking about for several years now.

Bike - Raleigh Tripper SS with disc brakes

Strongly recommend a full suspension, potholes at 25 mph w/ the extra weight will be painful.

 

[dogman dan]

I think 11 ah of the lipo can easily support 2000w, or 50 amps of power with no problems.

I do somewhat wonder why two motors though, since everything he wants can be had with one larger rear geared motor running on 30 amps.

 

[wesnewell]

A single rear motor is all you need. 1000-3000W, depending on what you want.
https://endless-sphere.com/forums/viewtopic.php?f=3&t=70169

 

[Mikebergy]

Two motors, for me, is to create balance in the design aesthetics. I prefer the smaller motors, visually, and like the idea of running with smaller components at lower power settings. I'm looking to run 500Wx2, not 1000Wx2.

 

[Jasonv8z]

What is the dropout width on the Raleigh? Most of the motors need 135mm or more with discs. If 25mph is all you need and you don't have major hills, you could go with a single Q100H and S06S or similar. Use a small controller to keep from frying the motor.

 

[motomech]

Why do you keep insisting that these motors are easy to "fry"?
Have you done it?
If so, please give the circumstances.
I only know of three on the entire internet, and they were seriously over volted.
It's the controllers, especially small ones, that are at risk.

 

[motomech]

I think what the Doubters here are over-looking is, there are other reasons to use 2WD other than in an effort to get high power.
My two Cutes can be out done in that regard my a single BPM on 35 Amps.
I'm using it at the lower end of the spectrum, as a single low power pedal assist, while retaining the ability to cruise cross town should the need arise. two Ebikes in one.
Let me ask this; You have a larger single motor on 35-40 Amps and you want a nice, smooth, natural PAS, how do you do it?
You could turn to Justin and get out your wallet.
Or, you could turn to BMS Battery and go with the current-limiting sine wave controllers. I was one of the first to try these and the first to come to understand that sine wave controllers and Lipo Voltages do not mix.
That leaves the square waves and the somewhat course 3-speed LED display. The problem with using powerful motors with these, is everything falls in between. Speed #1 is too slow while speed #2 is too fast. And with the first rotation of the pedals, the whole bike jumps. Ever seen a post here titled; "Help me tame my 17 Amp controller." No, I didn't think so.
Low power, low speed, makes for easy, natural assist experience on a budget. Even not using PAS, I can set the cruise on #2(15-16 mph), forget it and just pedal on top.

Then there is the issuse of un-sprung weight. At some point, adding weight to the end of the lever(chain stay), effects suspension performance. How much is too much. I'm not sure as the heaviest motor I have ever used is the Ezee, at 3.8 Kg.s. Yes, I knew it was there, but I wasn't riding off road. As far as the frt. is concerned, I wouldn't know the difference here either, as I have not owned an Ebike without a 2 Kg.s min on the frt.

Lastly, while I can't say my bike is particularly stealthly, I just couldn't use a pizza-sized DD motor. They just screem Ebike and I prefer to remain as low key as possible.

 

[Mikebergy]

Thanks, motomech. The low key aspect you mention is key for me. My chief complaint with both mass-produced and DIY solutions is that they are very much the 'look' of an ebike, that is, components are very noticeable, no subtlety. I'm not looking to make an ebike statement, nor am I looking for a quick and dirty solution. Looking to make something that looks nice and is functional. If my components don't mame sense from that perspective, I'll have to keep doing more searching.

I think that's the beef I have with most of the e-vehicles out there. Why does everything electric have to look borderline fugly? Prius? Volt? Fiat 500e? Leaf? Mirai? i3? All kinda fugly in their own way, whether it be a gross paint job, body kit/body design, or standout features. Time for the world to start making beautiful e-products rather than statements. Tesla kinda did it right although I still think aspects of the design are not well done.

 

[Jasonv8z]

Why do you keep insisting that these motors are easy to "fry"?

Sorry for the misunderstanding. I have never said these motors are easy to "fry". My suggestion was to protect the motor with a small controller. The controller has current and thermal limiting. The motor has neither. I'd rather under-size a controller than a motor.

 

[motomech]

My apologies then.
Actually, there is a Q100 used on a mid drive on this page right now.
It was destroyed......@ 48V and 35 Amps!
We do differ as to what is a safe controller though.
I have experiened the most heat, not only on the motor, but the controller especially, using the SO6S
Completely melted the phase wire connections one time.
My reasoning is this; The most damaging thing for small motors, aside from crazy high Voltages, is falling below 50% of the no-load speed while climbing hills.
My contention is, a controller of 17 to 20 Amps can help the motor maintain the speed above this threshold.
But the rider has to be aware of this threshold and if the motor falls below, shut down, get off and push.

 

[flat tire]

Don't do dual motors. It will totally screw up your bike's handling, decrease your efficiency, and besides that unless you weigh 300 lbs a single motor will be more than adequate for getting around town. Get a good battery, a controller from Lyen and you'll be flying. Make sure to figure out how many volts you need for the Kv of your motor so you will have an acceptable top speed.

 

[amberwolf]

Looking to make something that looks nice and is functional.

Have you looked at the EPO from Grindz145?
https://endless-sphere.com/forums/viewtopic.php?f=3&t=70440&hilit=epo#p1062567

 

[dogman dan]

No problem, I just wondered what the reasons for dual motor were. If the only reason is it will be fun and cool, that's ok.

Re the motor weight, the difference between a small geared motor and a large one is only about 2 pounds. Where two small motors is likely to be about 5 pounds heavier over all. And both easily put out 1000w.

So in terms of handling, I'll take 9 pounds on one wheel, vs 7 pounds on each wheel. I do understand reluctance to use a 14 pound dd motor, but two little motors combined will be about the same weight. So that's what I'm not getting.

One little motor won't fry running on 500w if the rider is not too heavy. But I can fry one motor in 30 min easily anytime. Done it several times. It's simple, too much weight, up too long a hill. This is why the company I work for recommends a 200 pound weight limit for one small gear motor, and a 300 pound weight limit for the larger 1000w geared motor.

Two smaller motors would be very hard to fry. Because under a heavy load each motor is running less watts, time to overheat will be longer. So if he's weighing over 250 pounds, then two small geared motors would stand hills better than one larger one.

Simple math, one big gearmotor best kept under 300 pounds. But two 200 pound limited motors gives you up to 400 pounds possible without undue strain on the motors.

 

[Mikebergy]

Looking to make something that looks nice and is functional.

Have you looked at the EPO from Grindz145?
https://endless-sphere.com/forums/viewtopic.php?f=3&t=70440&hilit=epo#p1062567

That's a nice looking bike, maybe the cleanest I've seen. Thanks for the link. I still want to build my own, but that style is close to what I want to aim for.

Also, dogman, for reference, I weight in at 180. I ride 150mi/wk in the spring/summer/fall, but slacking off this winter with only about 70mi/wk. I have no trouble peddling. My reasons for the smaller motors are aesthetics. The bigger DD motors are ugly in my opinion, weight is just a lesser reason for me wanting smaller motors. I like the dual motor symmetry, so the front and rear should be matching.
That being said, the specs for the cute motors are strange. I assume that when they say 48V201RPM, that is the unloaded rpm it will spin when 48V is applied? Why couldn't they just give a kV and a gear ratio? That is more standard to me.
A 201rpm motor @48V within a 700cc tire gets about 17mph if my calculator works, and that is too slow for me. Would it be better to buy a 36V201RPM motor, then run it at 48V? That would bump no load RPM up to about 24mph then. Or is there a better Q100/Q128 motor out there that would be better suited?

 

[Mikebergy]

Just got my batteries in today.
4x 6s 5200 Multistar packs. All of them are sitting pretty at 3.91V/cell.

Is BMSbattery the most budget-conscious place to buy the Q-motors? I am going to go with Infineon controllers from em3ev, and likely going to pick up a charger from there too if they offer one for 12s. I have a hobby charger to balance if I need to, but I plan on a BMS wired into the pack to make it a plug and play. Any suggestions on a decent programmable one and where to buy it? There are a few options out there, and I am not afraid to solder as needed.