Help pulling the trigger!

[woahdae]

I’ve been researching ebikes for a long time, and have been unable to pull the trigger on a new build so far. I did get a basic 250w front hub kit for my current bike, but that was always a stopgap. I would love a sanity check on my current direction, maybe it’d give be the confidence to drop the cash!

What I’ve landed on so far is a sport touring frame with a Falco (direct drive) 500w rear hub motor for a clean PAS experience, plus a geared 250w front hub motor like this one on a simple throttle for extra torque.

The requirements:

* #1, pull myself (~180lbs) and potentially 50lbs of stuff (kid, commuting junk, etc) up a mile long 7-9% grade at 15mph with a mild contribution on my part.
* 20mph cutoff is OK, don’t need/want to go much over 25 anyways.
* Lightweight, entire bike must be <55lbs to legally go on bus rack. It’s OK to remove the battery for this, but nice if I don’t have to.

Nice to have

* Street legal, i.e. 20mph & 750w. This is because I already want a light, torquey system that seems achievable with 750w, so why not. I’m always advocating ebikes among friends, co-commuters, etc, and if I’m not street legal I’ll get called out on it.
* Clean installation, minimal wiring. I don’t even need a display, necessarily.
* Regen for the long, rainy descent down said 7-9% mile-long hill to check my speed while carrying the kiddo without wearing on the brakes.
* Regen for charging ebike lights to provide a means to get home in the dark if my battery is dead.

Non factors

* Range. More is better, all things equal, but not a deciding factor.
* Top speed. I’m happy at 20mph, maybe 25. Actually once up to speed on a flat, the effort to stay at speed is the right amount of exercise for me.
* Cost. I don’t have a car, so in other words the money I would spend on insurance and depreciation can go to a bike!

So, torque is mostly what I need, and both the 500w and 750w falco motors claim 60nm of torque, which seems like just barely enough. The new Bafang 250w motors claim 42nm of torque, and only weigh just over 3lbs, so adding that gives 102nm total torque for a nominal weight increase.

I think I could get the 500w Falco system, and perhaps this controller and these cables and splice the 250w motor into the battery? Is it that easy?

So...

Does this make sense as per my requirements? Is there a better way to do the wiring? Also, 36v or 48v? Seems like 36v is the path of least resistance because the small front motors are 36v. I’d only care if it affected my ability to haul cargo at 10-15mph up 7-15% grades (usually max 9%). I’ve read lots of pages about max torque vs peak power, voltage, and such, but I’m going a little cross eyed now and can’t make sense of how it would affect my trip up a hill at relatively low speeds.

Thanks for any feedback. This forum has been extremely helpful so far, and apologies if something is obvious but I think I’m saturated at this point. Hopefully some advice can get me over the line.

 

[motomech]

What I’ve landed on so far is a sport touring frame with a Falco (direct drive) 500w rear hub motor for a clean PAS experience....

Street legal, i.e. 20mph & 750w. This is because I already want a light, torquey system that seems achievable with 750w, so why not.

If you are limiting yourself to a 750 Watt system, why do you need a large, hi-power capable $900 DD motor? DD motors like lots of power and something like a $150 BPM geared would be a better climber on a lowly 750 Watts.

I’m always advocating ebikes among friends, co-commuters, etc, and if I’m not street legal I’ll get called out on it(750 Watt system).

Is this for one motor system or two(get my point?)?

Regen for the long, rainy descent down said 7-9% mile-long hill to check my speed while carrying the kiddo without wearing on the brakes.

Regen is over-rated and one can buy lot's of brake pads for $750.

Regen for charging ebike lights to provide a means to get home in the dark if my battery is dead.

Lights consume very little power and if you are implying that you want the light to PEDAL home, well, I don't think you are going to like pedalling a 2WD ebike w/ lot's of batteries. 2WD by it's nature, has a back-up system and the idea is to carry enough battery capacity to not hit the LVC. It sounds like you will be doing the same route over and over, so it shouldn't be hard to know what you need and not have to press the range limit.
Which brings us to;

Lightweight, entire bike must be <55lbs to legally go on bus rack. It’s OK to remove the battery for this, but nice if I don’t have to.

A 2 WD ebike usually isn't mentioned w/ the word "lightweight". My 2 WD mountain bike w/ an Ezee geared in the back, a mini-motor in the frt and 25 Ah's of batteries weighs 70 lb.s. I think building a 2 WD anything w/ much of a battery pack would tip the scales at more than 55 lb.s.

20mph cutoff is OK, don’t need/want to go much over 25 anyways.

Which is it? There is a big difference between a top system speed of 20 mph and 25 mph. You need to pick the speed and select a motor speed range, whl. size and system Voltage to match.
In general, a low-speed motor (a 201 speed range), in a 26" whl. on 48 Volts will top out around 20 mph. A mid-speed motor(a 260) in the same set-up, will reach a 22 to 24 mph(You can use the motor sim. @ Ebike CA for this).
So what you want is;
1)Less than 55 lb.s
2)750 Watt system limit
3) 2 WD
4)Climb 7 to 9% grade for one mile

I might be wrong, but it just doesn't add up to me.
From a practical standpoint, I would throw that 750 restriction out the window and go with a single rear geared motor like the MAC 12T and a stout battery so you can run a 30 to 40 Amp controller, all from from Em3ev.
A BPM from BMS Battery could be the basis of a lower-priced system, but I'm not sure any of their packs can run a 35 Amp controller.
Sorry to seem so critical. Like I said, I could be wrong(but I don't think so , but better to hash these things out now rather than after you order the pieces.

 

[Chalo]

If you're trying to keep the bike weight down, two motors makes no sense at all. Just get a motor that's capable of 750W and has a relevant speed range. Set it up with both PAS and a throttle, and use the throttle as a "turbo" button. Right off the bat, you save the weight of a motor and controller.

 

[neptronix]

Falco can't be tuned, upgraded, or serviced easily. It's a completely proprietary system. I looked at their offerings years ago and they were making false claims about efficiency and the merit of 5 phase hubs.. it's all bs. There are some Chinese $150 hubs out there with better efficiency, lol.

I suggest you check out the ebikes.ca motor simulator. it can answer a lot of your questions about your power needs and what kind of battery you need. Another good place to look is the ebike photos and video section here. That's where people keep their build threads, and you can glean a lot of inspiration from there.

http://www.ebikes.ca/tools/simulator.html

 

[wturber]

The requirements:

* #1, pull myself (~180lbs) and potentially 50lbs of stuff (kid, commuting junk, etc) up a mile long 7-9% grade at 15mph with a mild contribution on my part.
* 20mph cutoff is OK, don’t need/want to go much over 25 anyways.
* Lightweight, entire bike must be <55lbs to legally go on bus rack. It’s OK to remove the battery for this, but nice if I don’t have to.

If you want lightweight, then you really don't want a 13 lb direct drive motor. Let's take my bike as an example. I have a basic aluminum frame mountain bike with a fairly stout frame. In standard configuration the bike weights about 32 lbs. Now add a 13 lb motor and we're already at 45 lbs. That leaves only < 10 lbs to add a battery and anything else like heavy duty rims and tires and racks and such which are pretty much needed to make the bike a decent car replacement. So if the < 55 lbs is a true requirement, you will almost surely be making a sacrifice in some other area. You may have to go with a less robust bike frame, less robust tires, smaller battery and less range or a removable battery.

* Street legal, i.e. 20mph & 750w. This is because I already want a light, torquey system that seems achievable with 750w, so why not. I’m always advocating ebikes among friends, co-commuters, etc, and if I’m not street legal I’ll get called out on it.

From what I can see, the 750 watt requirement is ambiguous in Seattle and will not be easy to apply to a home-built bike. It seems to be mostly aimed at stores selling pre-built bikes. To give you an idea of the ambiguity, just look at the kit ratings for the 750 watt Falco in this review that shows a nominal 750 watt motor with a peak output of 1200 watts. Bottom line is that that there is no such thing as a hard motor rating. You can measure motor power draw and motor power output - and those things will vary mostly depending on controller behavior. So look at the legal stuff closely and read this article by Justin. IMO, what is legal or not is significantly ambiguous and subjective. Proceed accordingly.

http://www.ebikes.ca/learn/power-ratings.html

https://electricbikereview.com/falco/hx-750/

* Clean installation, minimal wiring. I don’t even need a display, necessarily.

Clean installation is up to you and how much effort you want to put into it. Display or not will depend on local laws and whether you put together a Class 3 bike or not.
IMO, you want a basic display with speedometer, odometer and at least a voltage or power use indicator.

* Regen for the long, rainy descent down said 7-9% mile-long hill to check my speed while carrying the kiddo without wearing on the brakes.
* Regen for charging ebike lights to provide a means to get home in the dark if my battery is dead.

As already mentioned, regen for lights makes no sense. Lights don't use much power.

Coasting downhill is one of the most efficient ways of recovering energy. If it's legal and safe, coasting down a hill at between 25-30mph is a fine thing IMO. I'd take that over recovering .1 cents of power using regen while city commuting any day. And coasting downhill is FUN!

Regen makes sense if you are wearing through brake pads a lot and/or are doing long distance touring going up and down hills. But even then, it doesn't typically extend your range all that much. I'm thinking of enabling regen on my bike ONLY because I have about a mile of downhill through a gated HOA that is residential and has a 20 mph speed limit that I want to respect. I kinda dislike riding my brakes all the way through it. But that is a special case. I take full advantage of gravity on all the other downhill sections I deal with.

* Range. More is better, all things equal, but not a deciding factor.

Defining the range you need/want is actually a HUGE factor in determining bike weight and also cost. IMO, you want to think long and hard about how you'll use your ebike and what kind of range you'll want and need.

* Top speed. I’m happy at 20mph, maybe 25. Actually once up to speed on a flat, the effort to stay at speed is the right amount of exercise for me.
* Cost. I don’t have a car, so in other words the money I would spend on insurance and depreciation can go to a bike!

The Falco systems seem awfully pricey to me.

So, torque is mostly what I need, and both the 500w and 750w falco motors claim 60nm of torque, which seems like just barely enough. The new Bafang 250w motors claim 42nm of torque, and only weigh just over 3lbs, so adding that gives 102nm total torque for a nominal weight increase.

You seem to be treating torque as a static thing. It isn't. It varies with motor speed. Go play with the Grin motor simulator and look at what kind of motor controller combos are required to get you and your 50 lbs of cargo up a mile long 9% grade.

I think I could get the 500w Falco system, and perhaps this controller and these cables and splice the 250w motor into the battery? Is it that easy?

Adding a second motor makes no sense when you can get more torque/power by simply using a higher amp controller. What you really need to think long and hard about is whether you want a heavier, simpler, but more robust direct drive hub, a lighter, somewhat higher torque but still quite simple geared geared hub (that will be somewhat more prone to having problems if you push it hard a lot), or a mid-drive system that will give you the most flexibility and hill climbing torque since it drives through the bikes gearing system, but will bring with it a generally higher need for maintenance and will typically be more trouble to install. Note, only the direct drive system can easily accommodate regen.

So...

Does this make sense as per my requirements? Is there a better way to do the wiring? Also, 36v or 48v? Seems like 36v is the path of least resistance because the small front motors are 36v. I’d only care if it affected my ability to haul cargo at 10-15mph up 7-15% grades (usually max 9%). I’ve read lots of pages about max torque vs peak power, voltage, and such, but I’m going a little cross eyed now and can’t make sense of how it would affect my trip up a hill at relatively low speeds.

You probably want a 48 or 52 volt system IMO. I see no point in adding a small front motor for anything if you have a goal of keeping your weight low. You have said nothing about the length and frequency of your trips and why you need to get the bike on a bus. How many miles/year to you expect to put on the bike. It would be good to know how strict the buses are in enforcing the 55 lb limit as well.

It is good that you've gone to the trouble to define priorities. The question is whether you have defined them well or not. IMO, now is the time to take a second look and re-assess them honestly to be sure that you have them right. I remember when I was considering building my bike I almost bought a Cyclone mid-drive. Then I reminded myself that I'd be putting a LOT of miles on the bike commuting. So I sacrificed hill climbing for simplicity, durability and cost. I think it was the right call ... for me. That won't be the right call for everyone.

 

[woahdae]

I had a long reply to everyone on my iPad, but it seems to have been eaten... I'll try again, although I don't have as much time right now.

Thanks for everyone's critiques - It's all just ideas until I spend the money to put it together. Then I'm stuck with it.

One critique of the plan pretty much everyone made is that dual motors makes no sense, and the Falco is too expensive.

Here's one thing I like about the Falco that I'm willing to pay for: it's an all-in-one solution that's easy to install and has a good warranty. I've got a 10 month old at home, so my project time is very limited. The idea of tossing on a rear wheel and getting torque sensing pedal assist with a built in controller and wireless display is awesome. I haven't been able to find many people reviewing them, so they seem extremely botique, but if they deliver on their claims it sounds great. Bummer to hear someone say it's all BS...

Re dual motor idea, I think I read on this forum at some point that direct drive motors are very efficient at higher speeds, while geared motors are relatively more efficient on hills. Since the Bafang G370 weighs only ~3lbs, if it can draw from the same battery, the idea would be to get the best of both worlds by adding a geared motor in the front to help with steep hills. I swear I read that trick here somewhere. If it was 6lbs, though, I don't think it would be as interesting.

However, to many of your points about not needing dual motors, I played with the simulator a lot, and I couldn't get it to show me a real difference between various direct and geared hub motors as far as hill climbing was concerned. I mean, maybe a single MPH difference, and not always in favor of the geared hub if the DD hub was wired for torque. That suggests it's as academic concern rather than practical. Is that true? If I just run extra power to a DD hub, it'll be roughly the same as extra power to a geared hub?

I didn't try everything, but in general the only motor that got above even 12mph under my parameters on <750w (36v, 20a) was the Mac 12T (12.5mph). A Crystalite H3525 got 11.6mph (DD motor to approximate Falco, hopefully), and that extra 1mph won't be a deciding factor. This speaks to the point that I need more power than 750w to climb at my goal speed of 15mph under load.

Misc things.

Re 55lbs and "why bus," bus + bike is a car-killing combo, so I want to make sure I can do it as long as I'm building from the ground up. 55lbs isn't a hard limit, actually bus rack manufacturers set a total limit around 165lbs and Seattle Metro divides that by the number of bike slots (3) to come to 55lbs. So you could have two 70lb ebikes and an old rock hopper and still be safe. Bus drivers do have discretion, though, and if you need to lift your bike one wheel at a time they could decide to not let you ride. So it's more of a goal than a limit.

Re use case, I don't have a car, so my bike is used often and year round, about 2,000 mi/yr. That's the appeal of DD hubs - reliability. It's a shame they weigh so much, although the Falco only weighs 4lbs more than the MAC and doesn't need a controller.

The Mac 12T is a good recommendation, I hadn't seen that yet. Hill climbing is definitely a top priority, but I do like the seamlessness of a good pedal assist implementation. I like bikes that feel like bikes, ya know? I'm not excited to drill my BB to get it, although it's not out of the question.

I actually couldn't find much in the first couple pages of the show & tell section on the forum, aside from crazy powerful setups. I feel like I'm in a minority here that wants something relatively low speed and low fuss, am I wrong about that?

 

[wturber]

First, the 3 lbs for the front motor is actually 3 lbs plus the weight of the controller and wires. So I'd say that as a practical matter, it is 4 lbs. And if it weren't for you <55 lb target, I'd say, "so what?" But given your target weight, I think four pounds matters. I'd rather add that in extra battery range or extra racks/baskets/panniers if your target is car replacement.

As to the 750 watt limit and what is legal - you seem to be limiting yourself to 750 watts of power limit on your simulator runs. That seems logical. But I'm pretty sure that is wrong. Yesterday I thought you had the same ambiguity that is common with the three class system. But I looked up the actual law and it specifically refers to motor output. So let's look at your situation from that point of view:

http://lawfilesext.leg.wa.gov/biennium/2017-18/Pdf/Bills/Senate%20Passed%20Legislature/6434-S.PL.pdf

This is your situation with a Mac 12T running 36v 20amps battery draw for a motor draw of 731 watts. I have you on your 9% grade with 286 lbs (55 lb bike, 50 lb cargo, 180 lb rider.) With you working moderately hard, that gets you up the hill at about 11 mph.

http://www.ebikes.ca/tools/simulator.html?bopen=false&motor=MMAC12T&mass=130&grade=9&axis=mph

But take a look at the graph. The motor is operating at about 74% efficiency and is delivering only 544 watts - not counting mechanical losses to bearing, tires, etc.

Now if we take the situation above and replace the 36v battery with a 48v one, our hill climb speed improves by about 2.5 mph, and our efficiency goes up a tad. The batter power is 960 watts and the motor power is 733 watts. That seems compliant to me. That said, that setup could probably sneek past 750 watts of motor output. On a freshly charged battery operating at optimal efficiency, you'd be well over 800 watts. But with many controllers, you can implement limits so that you could almost guarantee that your motor would not go past 750 watts of power output.

If you really want to climb at 15mph, you are going to need more power and that means a direct drive if you want to avoid the mid-drive option. That adds weight at the motor, probably at the controller, and perhaps with having enough battery to drive the whole thing. That may very well push the limits of weight for use with a bus. But if you do that, you are probably no longer legal. Will that matter as a practical matter? I doubt it. If you operate reasonably and seldom go even to the 28 mph class 3 speed limit nobody would even have a reason to check. And even if they did, that 750 watt sticker you could stick on your motor would probably be enough to convince any LEO that you are A-OK on a legal bike. But will it matter to you personally that the bike isn't really legal? I dunno. That's your call. Maybe you'd rather be legal and go up that hill a tad slower. It's your call.

 

[wturber]

I actually couldn't find much in the first couple pages of the show & tell section on the forum, aside from crazy powerful setups. I feel like I'm in a minority here that wants something relatively low speed and low fuss, am I wrong about that?

No. Your situation is very similar to mine. The main difference is that I dislike buses and don't want to ride them. My bike is 65-70 lbs and has a 50+ mile range. And while I've had my bike pulling over 1000 watts in the past, right now it can only do that on a very fresh battery for a very short time period if I go full throttle or set my PAS to the top level of 5. But as a practical matter, I never do that. My top PAS level right now supplies about 650 watts of battery power which is probably closer to 500 watts of actual motor power - and I probably use that level about 30% of the time. So most of the time, I'm using less than 500 watts of motor power.

My long uphills are probably closer to 6% than 9%, but I do have some short 15% grades. I don't pull 50 lbs of cargo and I weigh closer to 165 lb most of the time. If I needed to pull more cargo frequently, I'd probably go back to pulling closer to 1100 or 1200 watts from the battery to get some extra help. But even tho the motor could output more than 750 watts in that configuration. As a practical matter I'd seldom do that. I'd typically be on full power to climb a hill and with the lower speed my efficiency would also be low. So I'd probably never actually exceed 750 watts of motor output - even though the bike could technically do that.

 

[Chalo]

The one single factor by which you should choose between geared and direct drive hub motors is this: Do I ever want to ride the bike without using motor power? If the answer is yes, you should discard the idea of direct drive motors. They are depressingly draggy. Not impossible to ride unpowered, but no fun at all.

Having lived in Seattle for six years, and having used bicycles, e-bikes, and motorcycles for transportation there, I think a hub motor is not a good choice. A mid drive that allows you to change the motor's ratio by using your gears will work better on the wide range of street gradients in Seattle. Resign yourself to the idea that you'll need a replacement chain and cassette a lot more often than before. It's not a big deal. And you won't need very much motor power to do everything you want to do.

My first Seattle e-bike used a shafted scooter motor with 12:1 reduction gears to a freewheeled left side sprocket. My second one used a big heavy direct drive front hub motor. The second one was much more powerful and had multiple pedal gears, but the first one felt more versatile despite having only one gear for the motor and one for the pedals. The main difference was the lack of drag while coasting on the earlier bike.

Now I use a Bafang BBS02 on a cargo bike that would be slow and tedious without motor assist. I can go as slow or as fast as I want, and the motor works equally well regardless.

 

[woahdae]

Awesome, thanks for the feedback. The kiddo didn't sleep much, so it's one of those stare-off-into-space days for me. I'll have to use tomorrow's brainpower for this.

Good point about direct drive and drag. Falco claims no drag, is that BS?

 

[neptronix]

All direct drive motors have drag. It just depends on how much.
Falco had some half decent laminations in their initial which decreased drag over the motor they considered was their competitor, the Crystalyte H35xx series..

But any motor, other than the most garbage of 9C clones has those 0.35mm laminations now. Drag is very low.
On my 35mm wide Leafmotor, drag was so minimal that i could pedal with only 1-2mph of loss. Not a big deal.

If you want imperceptable levels of drag, a geared motor is the way to go. And geared motors are significantly lighter, too. But then you lose regen capability.

 

[donn]

I don't have a lot of experience behind me here, but it's all in Seattle and it's with direct drive hub motor. I did have to pedal it home last week, when I ran out of juice. It was slow, and some of that was drag, but I think weight has a lot to do with it. I have a "1500W" kit from West Coast Electric Cycles. It's quiet and works well, but it is heavy, and then there's the battery. Really no complaints, about the motor - I think my main complaint at this point would be the bicycle with no suspension, vs. condition of the roads and trails around here.

I certainly agree with the general sentiment (if I read it right) that you could get what you want from one hub. I'm not 100% confident that I'll never get into some kind of trouble over my setup, which is technically over powered, but I think the way to avoid that is not ride like a nut. They're not going to look at me pulling out from a stop and say, "hm, that guy on the recumbent has illegal amounts of acceleration!" It's the 40mph stunts that are going to bring the heat down. I do really like it, for acceleration and maybe for the occasional really steep hill, but honestly I don't pull over 750W all that much, and the cargo bike crowd seems to be pretty happy with theirs.

I love the recharge with the WCEC setup. I'm getting maybe 9% back, and it's a very nice braking effect. It's null when the battery is dead, though. I don't know if it would go into the lights - maybe, I doubt it.