Just more than a bike (low power / low consumption)

[Jil]

I start this post to continue the discussion started on the "Bafang M500-M600 thread" :

Grin estimates that the GMAC (no freewheel) has a drag around 20-30 watts at usual speed, you can estimate that on a motor with freewheel it’s less than 10 watts.
As for the additional weight, I have made the calculation on Grin’s motor simulator, 10 kg more represents around 10 watts at reasonnable speed on steep hills. So, finally, on a motor with inner freewheel, the power needed to compensate the additional weight and drag is 20-30 watts only.

I have tested my GMAC yesterday and today with very low power (electrical assist between 30 and 50% of my pedaling power), I felt very clearly the electrical assistance (100 watts when I put 200-250 watts of human power), making the ride more enjoyable than without motor, and keeping the consumption very low (around 4 Wh/km).
That’s another way to use ebike, which I’m not really used to (the former version of my GMAC was mainly for fast commuting at 1000-1500 watts) but which I enjoy also.

Are you using a low-powered ebike ? max 500 watts peak power and 250 watts average power.
If yes, what is your usage, your setup, your consumption depending on the conditions ?
What is the adavantage you see in using low-powered ebike ? More sport, more range, less batteries, less weight... ?

 

[markz]

Define low power?
Is it 500W and below

With average power being 750-1000W and high power being 1500W+

I recently am going much slower while riding, I want extended range. The old battery used to get 22km of range of normal use, 25-32kph but if I go slower I measured 40km range, 750wh of battery. Which makes me want to look into pedal assist because people find its better then throttle, will force me to pedal, but at times I want to use cruise control so maybe look into a pas bypass. That just came to me now. I'd have to look into if my Greentime controller has pedal assist, if not its an added cost.

 

[Jil]

As for the additional weight, I have made the calculation on Grin’s motor simulator, 10 kg more represents around 10 watts at reasonnable speed on steep hills.

To illustrate this, on the Col du Tourmalet, one of the hardest of the Tour de France, 10 kg additional weight (a medium electrical system) represents only 11 watts of addtional mechanical power.

A bike+cyclist of 100 kg at 125 watts (https://ebikes.ca/tools/simulator.html?motor=MG310_STD&wheel=28i&cont=PR&throt=0.001&hp=125&mass=100&grade=7.3)
climbs at the same speed than
a bike+cyclist of 110kg at 137 watts (https://ebikes.ca/tools/simulator.html?motor=MG310_STD&wheel=28i&cont=PR&throt=3.5&hp=125&mass=110&grade=7.3)
--> that's only 12 watts of difference. Concering the drag, it's really minimal if the motor has an inner freewheel, like the Bafang G310.
It appears that the additional power needed to compensate the weight/drag of an electrical system is often overestimated.

 

[Jil]

Define low power?
Is it 500W and below

Let's say below 500 watts of peak power, and maximum 250 watts average power.

 

[markz]

Do not forget about aerodynamics, it really does help out a lot.
Just read something about the magic #, being 25mph with wind resistance becoming a major factor in over coming it, so if you go recumbent you can still pedal hard yet have a lot of aero to increase distance, lower consumption and continue on riding. I don't see to many "laying on the ground" recumbents, nor do I see many upright recumbents. The ones who lay on the ground startles you at first, but they usually have one big bright flag. I see one guy on a velomobile, its yellow, see him in the oddest of spots and I still dont know if he is electric or not. First time was downtown Calgary by a memorial teepee, next was far away so he gets around, just like me. I get around, in all parts of the big city.

 

[pickworthi]

Are you using a low-powered ebike ? max 500 watts peak power and 250 watts average power.
If yes, what is your usage, your setup, your consumption depending on the conditions ?
What is the adavantage you see in using low-powered ebike ? More sport, more range, less batteries, less weight... ?

LoL - asking about low power on a USA dominated forum, I don't think they believe that 250W exists

For me:
- Generic Shengyi rated at 250W "maximum continuous power" (sic), supplied by Dillenger
- Cycle Analyst V3 and Baserunner controller, configured for 500W max power, and 16mph max assist speed
- PAS only
- Built on a Dawes Galaxy AL (2013) frame (aluminium tubing)
- A variety of self built and Dolphin batteries ranging from 10aH to 21aH capacity. Carried in front panniers (Ortlieb) mounted on Tubus front rack.

My use case:
I am a recreational cyclist, but getting on a bit. Ok, a lot. I don't have stamina or power to do the 50+ mile rides any longer, but I still want to. So this PAS setup is the answer for me. Enough power to sustain a 15 mph average over 100 + miles (did that in September - great ride).

Also, avoid drawing the attention of any busy body / law officer by riding obviously too fast. (Recent press report of e-bike in Wales confiscated and destroyed after being witnessed riding up a hill without pedalling, so it is happening.)

 

[dogman dan]

Back when I was riding the big monster of a touring bike, worst possible aero, My goal was to get from a to b without using more than 200w on average, as measured going into the controller. This bike had the big 25 pound 5304 crystalyte motor which was needed to get the big load up the rocky mountain passes. So we are talking about a huge heavy bike, with enough crap on it to need to go slow. 20 mph cruise without pedaling could cost you 800w.

But if I ran it at 15 mph on a day with no huge headwinds, I could hit that 200w number, pedaling up enough of the total wattage to really increase my range. I did not need PAS, since I always loved to pedal anyway. It worked great to run this monster motor at 200w and 15 mph. I rode it 15 mph on the flats, and 15 mph up a 6 mile long mountain pass kept it running efficient enough. Somehow you just don't think you can ride a small motorcycle rear hub bike at 200w. But you can, just by slowing down and pedaling moderately hard. I just learned to feel the pressure on my feet, and when it got too light back down on the throttle. With practice, it became automatic with no thinking at all, and worked better than any dumb pas. (without torque sensing) My feet could sense the torque just fine.

You bet it took some getting used to, riding that slow. But given the bike I was on, it was going pretty good. Pedal only, I was hard pressed to keep up 5 mph. But in the right gear, I could throttle to 12 mph, and pedal up the rest easy. I got the range I needed, since some of these rides out west are 60-80 miles plug to plug.

 

[dogman dan]

Re riding to eliminate the drag of the weight and the DD motor resistance, I always estimated it at about 50w. My bikes tended to run heavy in battery. But in practice, with a throttle at least, its hard to actually ride at 50w. But you can hold a throttle at 100w, and ride with just about 50w of extra assist. I did this to limp home on a near empty battery plenty of times. Systems with 5 power levels can be set on the lowest power level, and still get a decent assist on a hill, or start, then revert to pulling only 50w or so on the flat if the rider pedals and keeps the speed down. So you don't have to have pas.

The catch 22 of riding like this, at 100w is hills. Yes, you can ride up a hill with just 100w assist. But if you do this with a hub motor, you end up running the hub motor too slow for its rpm to be efficient. Then the dang thing makes 60w of your power into heat. So you turn it up to 150w, still don't go any faster, but now its making 90w into heat. Put your hand on a 60w incandescent or halogen light bulb sometime and turn it on. You won't keep your hand there long. This is why my touring cargo bike had the capability and motor size to pull 2000w up the mountains, keeping it cool and efficient on the hills. I just ran 15 mph up the hill, 25 down it, and 15 again on the flat. I never ran the motor too slow to be efficient, even with full loads of camping gear.

So the low power hub motor is great, till you get to a big hill. Then you just piss away your assist into heat. Fine if you live where its pretty flat. Holland, Florida, West Texas, Manhattan, etc. Everywhere else, a 250w bike really needs to be a mid drive, so you can gear down. Then the rider needs to be smart enough to gear it down. :lol:

 

[Jil]

So the low power hub motor is great, till you get to a big hill. Then you just piss away your assist into heat. Fine if you live where its pretty flat. Holland, Florida, West Texas, Manhattan, etc. Everywhere else, a 250w bike really needs to be a mid drive, so you can gear down.

I agree. A small mid-motor is much better for this. You always run in the good range of efficiency, even at 5 kph. In addition, running low power allows to avoid what is, from my point of view, the major issue with mid-drive motors : accelerated wear of the transmission.
Among off-the-shelf mid-drive systems, Fazua looks to me like the sweet spot for this type of use.

 

[Jil]

20 mph cruise without pedaling could cost you 800w.

But if I ran it at 15 mph on a day with no huge headwinds, I could hit that 200w number, pedaling up enough of the total wattage to really increase my range.

That's exactlly the point of this post :wink: The need for power increases exponentially with the speed.

 

[AHicks]

I have 3 bikes. 1 is powered with a MAC 12t geared hub and because I ride for recreational purposes only, average speed maybe 12mph, the bike is generally pulling less than 200w (likely closer to 125w). Clearly, when I need to go faster for some reason, or if I'm faced with a large hill for instance, the bike is capable of pulling WAY more power (1000w+)....

Bafang Ultra mid drive bike - same story as above. Will loaf along pulling very little power until you ask for more, which it is very capable of delivering!

Newest bike, and the lightest of the 3 by quite a bit (55lbs vs. 65-70lbs) is equipped with a 500w geared hub. It's generally pulling less than 200w as well in most conditions. Because the bike is so light, it's a delight to ride! What may make it a bit different, is the fact the controller on the bike is able to supply the motor with up to 1000w.

I'm here to tell you 1000w fed to a 500w motor makes for some pretty sporty performance! The thing is you need to have the brains to tell you that power needs to be used with a certain amount of caution to keep the motor from burning out. Crossing a busy road might be a good application, as would catching up with a riding partner or climbing a short hill. Climbing a long hill, that might take several minutes to climb, would be an example of something that's certain to shorten the motor's life expectancy....

What I've learned, is that all 3 bikes pull about the same amount of power at my average cruise speed. All are pretty sporty at wide open throttle. 1 bike, the 500w bike, is more fun to ride, and the thought is that's because it's lighter.... FWIW, -Al

 

[docw009]

Yes, I have four low power ebikes. They use the Q100H motor on 20" wheels, three powered with a 20A KT controller and one with a 25A KT. I usually run on 36V, but put two of them on 48V this summer/ We ride them slow, at 12 mph and the KT LCD3 display show 80-120W. So 1 hour is 12 miles, 100WH, and about 8WH/mile. My wife, 80 pounds lighter than me, is more like 5-6 wh/mile at these speeds. The bikes are light, pedal easily w/o power, and 100W more than takes the edge of pedaling. On the other hand, put into PAS4, they will cruise at 18-19 mph with easy pedaling too.

In contrast, my fat tire bikes are 2X the weight. They have similar KT controllers/displays, 500W fat tire motors, and 100W on those bikes requires high effort pedal assist, especially on slight inclines. Too much like unpowered biking, I need about 200+ watts showing on the display to feel good. Power consumption for me, at slow speeds is more like 10-12 wh/mile.

My first conversion is a 500W geared hub motor with a 22A 36V controller, and 36V10AH battery. That's 360WH, Some folks would not call it ebiking, but several years ago, when the battery was already 4 years old, I managed to sqeak out 60 niles on it. The last 6 miles was at 32V, with a very light touch on the pedals to keep it from sagging the battery under LVC,

If Grin says their GMAC is only 30W of drag, OK. That's a lot to me.

 

[Mclewis1]

I have 2 bikes, each with ~500w Shengyi SX geared hub motors, BaseRunner controllers, CA3s (same setup except for wheel size), cadence PAS + throttles, and a 52v 14 amp/hr (750w) battery. I'm 6' 2" and around 210lbs, but older (62)

Normal riding is done with about 200w of assist (PAS level 2), the throttle normally only gets used crossing streets or navigating in parking lots or around obstacles. Rolling hills get 300-500w, and around 1000w (throttle) on the nasty short steep sections or accelerating in city traffic.

The around the city in all conditions bike - Surly Bridge Club (steel touring/trail bike), flat bar, 2"/50c tires, fenders, rack, small panniers. About 55lbs as ridden. Around town I'm in the 13w/m 8w/km range, with average speeds in the 14mph/22kph range. On the open road and without the panniers I can get into the 12w/m high 7w/km and average around 15mph/24kph.

The fun longer distance road bike - Surly CrossRoads (steel road/gravel bike), flat (but soon a drop) bar, 700x37 tires. About 40lbs as ridden. Average speeds on the road in the 18mph/29kph range at 11w/m 7w/km. The expectation is with the drop bars that the efficiency should get even better, dropping into the mid 6w/km range.

While avg speeds obviously drop in the congestion of the urban trails and city traffic it's the start stop that really seems to affect the w/km. On the open road the 2nd bike is showing much better efficiency numbers (as expected) but also at substantially higher avg speeds. Very limited start/stops helps, but a bigger part of this difference is using more appropriate high speed gearing while maintaining a similar amount of assist. The city bike's high end is only 32x11 so I spin out in the 30kph range (I'm really not helping much above 28kph or so) but the more road bike setup has up to 52x12 gearing allowing me to continue to really push well above 30kph. So while the assist is still averaging 200w the output from the protein motor (me) is actually increasing at higher speeds. This also means that by changing my riding style a bit (increasing my output while keeping the speed down) should further improve on the w/km, extending the range of the battery to well over 100km.

After a little learning, most of my hill climbing is now best done at the fastest speeds possible/practical, normally with a max of 500w of assist. This has usually kept me from overheating on all but the steepest sections. The CA3 in it's default setup is starting to roll back power at 90°C and at 500w it doesn't take too long (few minutes) for me to start bumping into that point when climbing (and only a short time at 1000w).

 

[LewTwo]

Well as long as you folks are talking "low power", you do realize that small front wheel geared hubs tend to work well as well. Less encumbrance with various gear systems as well

 

[Mclewis1]

Well as long as you folks are talking "low power", you do realize that small front wheel geared hubs tend to work well as well. Less encumbrance with various gear systems as well

Ah yup, sure do. The city bike I mentioned in the post above is a front hub setup. It's worked out very well but that rigid front wheel just isn't very comfortable on my hands on 3+hr rides unless I really soften it up by running much lower tire pressure (not really appropriate on longer distance road rides). So when I decided to add the assist to the road bike I went with a rear hub setup to keep the front end as compliant and comfy as possible.

 

[dogman dan]

All of those above posts confirm the conclusions I came to 12 years ago, when I first started reviewing different hub motors. DD or geared motor, they all got real similar efficiency on the open road. At 20 mph and no pedaling, all took just about 500w. 400w is possible, but I was riding a bike with no aero advantages. These tests were done on identical routes of 8 miles, on the same bike, in the same weather. What I mean is the type of motor did not matter a whole lot on routes with few stops and only very mild grades. Btw, this was all front motors at that time. Rears were rare at that time. Front or rear does not matter for efficiency when its street riding.

Once you added a stop sign 8 times a mile, then the motor type and winding made huge differences.(still no pedaling) A slightly fast DD was 20% less efficient than a geared motor of typical 36v rpm winding. But you could eliminate that difference by how you rode. Pedal for 20 feet on the starts and the DD got efficient again.

The best bet for a hub motor e bike is of course, lower speeds, lots of pedaling, and a 20 inch wheel. The very most efficient bike I ever built was the one that burned in my garage fire. It had a 20 rear hub of the 9c type, but a 10 T wind that gave it a 48v top speed of 18 mph. The wind did not make it more efficient per se, but being completely unable to exceed 18 mph DID. While the 20" rim gave it the torque required to pull a large trailer. When the fire happened, I had just built the coffin trailer designed to carry a bed inside, and 50w of 48v solar on the lid. Unfortunately, the fire kind of ended those ideas of touring by e bike for me.

This bike would have done good in Chile. It was designed to haul a huge trailer, a really tiny house, and the thing could carry 4 kw of battery with ease.

 

[Mclewis1]

Dan, You've raised a question I've had for a while. It's been discussed back and forth within some of the other discussions but there doesn't seem to be much specifically on the subject and difficult to search on.

So a question or discussion for everyone ... Fast wind vs. slow wind hub motor cores (a question that seems to be appropriate in a thread about lower wattage motors and power consumption/efficiency).

I know the general wisdom is to select regular/slow wind for larger diameter wheels (say 26" and above) and fast wind for smaller ones (26" and smaller). I understand the general reasoning for this with the desire to keep the motor in a more efficient rpm range and more commonly to just be able to have a faster bike. The other general wisdom is that hub motors don't climb as well as mid drives primarily due to gearing. Personally I've observed the benefit (efficiency and heat avoidance wise) of climbing at a faster speed with my geared hub motor bikes.

With the desire to run lower wattage motors and if there isn't the need or desire to max out the top speed potential (just as happy with a 35kph top speed vs 45kph potential) and instead a desire to climb more efficiently could it make sense to choose use a faster wind motor with the larger diameter wheels? This should cause the motor to spin faster at a lower overall speed while climbing hills which should equate to a bit more efficiency (not bogging down until much lower forward speeds).

 

[ZeroEm]

You may have misstated your meaning. Larger wheels do not speed up the motor, unless i'm not understanding. Maybe your talking about a Inrunner or Middrive of some type then wheel size does not mater.

With the desire to run lower wattage motors and if there isn't the need or desire to max out the top speed potential (just as happy with a 35kph top speed vs 45kph potential) and instead a desire to climb more efficiently could it make sense to choose use a faster wind motor with the larger diameter wheels? This should cause the motor to spin faster at a lower overall speed while climbing hills which should equate to a bit more efficiency (not bogging down until much lower forward speeds).

If you have not had any luck finding debates on this topic, search John in CR

The winding's should be chosen and matched to your setup and riding style. Not going to debate the pro's and con's. You decide what you want. High speed, small wheel, high amps and Low Turn motor. Low speed, any wheel size, any amps and More turns in the motor.

Example: I wanted 26" wheel, 72v battery, controller limited to 40a and top speed of 30mph. Picked a winding that would fit this setup.

 

[Mclewis1]

No, larger wheels don't simply speed up the motor ... but the question is about the matching of faster wind geared hub motors with smaller wheels and slower or regular wind motors with larger ones. We've done this for years for various reasons. I'd like to find out if there may be a benefit for changing up this traditional matching if someone's prerequisites are a little different (more emphasis on better hill climbing vs. higher speeds). Assume keeping the other variables the same (same controller, voltages, etc.).

thanks for the search suggestion. I've read many of John's posts on this, as well as quite a few others. Part of the issue I've had is trying to break down many of the points involved. Many of the conversations seem to devolve into the benefits of more amperage and higher voltages (of course very true).

Maybe I can put the question into a different format. What happens if you have a bike with 700c wheels with a standard wind hub motor and then all you do is swap out the hub motor for an identical but faster wind version. Yes, it will "top out" at a lower speed, but will it climb any better? Better = would be able to climb using a higher gear at the same assisted power levels.

Or instead of better being faster speed while climbing, since there's a point at lower rpms where a geared hub motor really starts to lose efficiency and the torque levels drop off (it "bogs" down), would a faster wind hub motor take longer to reach this point? (as the human can't maintain his/her output and continues to gear down)

edit: changed the fast wind to higher gearing question and add the lower speed addition.

 

[Jil]

So the low power hub motor is great, till you get to a big hill. Then you just piss away your assist into heat. Fine if you live where its pretty flat. Holland, Florida, West Texas, Manhattan, etc. Everywhere else, a 250w bike really needs to be a mid drive, so you can gear down. Then the rider needs to be smart enough to gear it down. :lol:

On a long and steep hill, with low power, it's not so clear finally.
When you are in the 20%+ range (MTB), no contest the mid-drive is much better.

But for example on a 10% hill, with 150 watts human power and 150 watts electrical power, 120 kg total load (i.e. loaded bike for travel and 70-80 kg cyclist), the difference between mid-drive - BBS02 - and small hub motor - G310 - is not that high (4.3 kph without motor, 6.9 kph with the hub motor, 7.6 kph with the mid-drive) :
https://ebikes.ca/tools/simulator.html?motor=MG310_STD&cont=BRL10&wheel=27.5i&hp=150&grade=10&autothrot=false&throt=21&cont_b=BRL10&motor_b=MBBS02&wheel_b=27.5i&hp_b=150&throt_b=7.7&grade_b=10&bopen=true&mid_b=true&gear_b=1&tf_b=30&tr_b=34&mass=120&mass_b=120

 

[Manbeer]

Going against the grain here with my Just more than a bike being mid drive, but i was a huge fan of the TSDZ2 for that purpose. It did more with less power than pretty much anything else i have used.

If i put in a brisk walking level of effort (100-13x watts)
9 watts per mile got me in the 17s, If I put it in a fitness level of effort, 12-13 wpm would see me around 22mph under normal conditions. This was on a hybrid with fat slicks, So it was a somewhat efficient set up to begin with. 40 miles range from a seat bag battery with 13s2p 21700s- As long as you didn't want to go to fast or get a free ride, it did it all well. Even had it on a Hardtail 90's stumpjumper for a while and it was good off-road, On a pretty heavily used local trail here I was logging the ride on strava once And accidentally left it on bike rather than ebike and when I went to finish I had a bunch of top 10 segment times On a 25 year old Frame with 2 inches of suspension travel in the front only, crappy tires and worn rim brakes

 

[COAR]

43450474-DD1B-43F5-8BB7-8FD0EAD692B7.jpeg

Perhaps it's more obvious from the left side, but that is probably the stealthiest conversion I've seen.


As for the original topic, I have a BBS02 that is about 850-900w peak but I ride almost exclusively in the lower PAS levels (<5 out of 9) which means my real world peak output is well under 500w. I'd guess my average while cruising barely breaks 200. Use case is recreational mt biking on a variety of singletrack. I'm still putting in probably 1/2 to 2/3 of the effort I do on a normal bike, I can just go faster and/or farther than I would with pedal-only. I would be OK with a 'detuned', true 500w peak motor but the current mid-drive options don't really offer a significant weight savings over my setup.

 

[markz]

I'd love to get that kind of wh/mile, to much work, to much "breaking a sweat" for my liking.
From 750wh I got 40km, babying it, going slow and pedaling 70% of the time.
Today I rode behind some Bosche people, maybe it was Shimano mid drive but they were flying and they always had to pedal. If I had gears maybe I would put effort into my riding, I got a wobbly crank 1x and 7 rears.

I felt as if I had to keep up to those 2 people on Bosches or whatever, so I wasted a lot of juice, throttle only behind them. Luckily I got my spots to juice up, $2.50 Starbucks which broke my rule to buy anything from them.

40 miles range from a seat bag battery with 13s2p 21700s- As long as you didn't want to go to fast or get a free ride, it did it all well.

 

[99t4]

So much room in that triangle (more of a trapezoid?) for a nice big battery-- in some weird way it seems like a waste for such a minimalist battery on that frame. :lol:

Guess I have been looking for too long at possible donor bikes from the standpoint of "how much battery can it hold?"

 

[dogman dan]

RE the slow winding motor I chose for that efficient bike. I chose slow motor and small wheel combination solely to make going above 18 mph impossible, unless downhill. Downhill I'd coast, or coast while tickling the throttle just enough for it to coast faster. Most of this bikes efficiency came from the 20" wheel, and never riding 20 mph or more. Could do the same thing with a cycle analyst, setting speed limit to 18. But I was running a controller with no CA plug.

The small wheel was for torque, which made it climb a hill efficiently despite 400+ pound loads. This combo would not get too inefficient until loaded to the point ( with grade or weight or combined) where its max speed was under 10 mph. For a typical hub motor, 26" wheel and normal rpm wind, this is more like 15 mph.

So if your situation, combined grade, weight, and pedal effort results in 15 mph, any hub motor however low power will still climb with good efficiency. When I was doing extensive testing for E-bikekit.com, I was exploring various loads in weight by towing a trailer full of sand bags or water jugs, and climbing hills in extreme weather conditions, like over 105 F. The combined data we got led us to be able to offer a very long warranty that was conditional to the buyer not overloading the motor with much more than 300 pounds of weight. EBK also stopped selling motors that could not carry that much load, without maintaining 15 mph up an 8% grade, without pedaling.

The overall conclusion was, overloading the motor is the real issue. The overload could be a 20% grade, a fat ass, or a trailer full of cargo. But the motors EBK was selling all ran at 750w or 1000w max watts, which I don't call low power. They just stopped selling a small motor that lacked enough magnet and copper to pull a big load without slowing down too much. They were replacing way too many of the lower wattage rated geared hub motors to make it profitable. Usually the customer getting a new motor lived where hills are steep and would not pedal much, or at all. This change just about eliminated motor replacement warranty issues.

But a low wattage motor can pull a very fit guy up a hill, folks that can pedal up 8% at 10 mph only need 5 mph of assist to get into that efficient hub motor rpm. Most of us though, walk a bike up 8%, that's why we bought e bikes.