-
Howdy! we're looking for donations to finish custom knowledgebase software for this forum. Please see our Funding drive thread
Low Weight, Low Power E – ASSIST
- Thread starter jmygann
- Start date
jbond
100 W
- Joined
- Oct 1, 2010
- Messages
- 204
Nice 'bent Jeremy. Please excuse my Brit bluntness, Kepler. I didn't mean to be rude. Please excuse me.
My current ride is an Alien Aurora. This has the Bafang BPM motor. Claimed 350W@36v with a Phylion 36v-10Ahr batttery. Wonderful as it is, it's too heavy, range is too short and there's a bit more drag than I'd like from the motor. All of that makes it less fast as a bicycle than my Ridgeback Hybrid. On the up side it will go up any hill I can throw at it at a perfectly acceptable speed. I don't think I actually need the 350W and a 250W motor would be adequate. With a lighter, more free running bicycle I think the range would be a lot better with a more intelligent controller strategy. Hence my thoughts above. What I'm aiming for is two things.
- Take the sting out of hills, even seriously steep tracks off road.
- Enough power to get my pedaling average over 15mph on the flat.
What I don't want is an artificial speed limit on when that power is available either for legal reasons (UK-EU 25kph limit) or because it makes the controller simpler.
As far as I can tell, the Infineon controller is still speed limited where what I'm after is something that is power limited.
Bafang do a 250w 1.9Kg hub motor. With some attention to drag plus less weight, I should be able to get more range from say 2/3 of the battery. That should get the battery+motor under 5Kg, perhaps down to 4Kg.
The Gruber just looks wrong to me. And on a conventional bike, hub motors look better and simpler to me than other options. Cyclone-style dual freewheel, chain drive motors look perfect for recumbents but it's hard to make them look neat on a head first bike.
My current ride is an Alien Aurora. This has the Bafang BPM motor. Claimed 350W@36v with a Phylion 36v-10Ahr batttery. Wonderful as it is, it's too heavy, range is too short and there's a bit more drag than I'd like from the motor. All of that makes it less fast as a bicycle than my Ridgeback Hybrid. On the up side it will go up any hill I can throw at it at a perfectly acceptable speed. I don't think I actually need the 350W and a 250W motor would be adequate. With a lighter, more free running bicycle I think the range would be a lot better with a more intelligent controller strategy. Hence my thoughts above. What I'm aiming for is two things.
- Take the sting out of hills, even seriously steep tracks off road.
- Enough power to get my pedaling average over 15mph on the flat.
What I don't want is an artificial speed limit on when that power is available either for legal reasons (UK-EU 25kph limit) or because it makes the controller simpler.
As far as I can tell, the Infineon controller is still speed limited where what I'm after is something that is power limited.
Bafang do a 250w 1.9Kg hub motor. With some attention to drag plus less weight, I should be able to get more range from say 2/3 of the battery. That should get the battery+motor under 5Kg, perhaps down to 4Kg.
The Gruber just looks wrong to me. And on a conventional bike, hub motors look better and simpler to me than other options. Cyclone-style dual freewheel, chain drive motors look perfect for recumbents but it's hard to make them look neat on a head first bike.
Jeremy Harris
100 MW
The Xiechang controllers (wrongly referred to here as Infineons, even though they stopped using the Infineon controller chip a year or so ago) are certainly speed-controlled, but not speed limited (unless you deliberately choose to programme them to be). By speed controlled, I mean that the output voltage to the motor is directly proportional to the input voltage from the throttle. This isn't the way the throttle works on an internal combustion engine, so feels a little odd at times and tends to give poor low speed throttle control, especially at high motor/controller power capabilities.
We're more used to a throttle control that determines torque, rather than motor rpm, as this is pretty much what the throttle on a car or motorcycle does. In the case of an internal combustion engine, the throttle sets the volume of mixture admitted to the cylinder(s) which directly corresponds to the brake mean effective pressure that the piston(s) exerts on the crank. This is pretty closely matched to the shaft output torque.
There is a current limit on the Xiechang controllers, in fact both linear limiting and current peak shut off protection. The linear current limit mode effectively sets the maximum torque that the motor/controller will deliver, by reducing the commanded PWM duty cycle when the supply current exceeds the programmed level. In effect, this tends to give power limiting, as it fixes supply current (but not phase current) whilst allowing the motor current and voltage to change in accordance with the applied load.
Jeremy
We're more used to a throttle control that determines torque, rather than motor rpm, as this is pretty much what the throttle on a car or motorcycle does. In the case of an internal combustion engine, the throttle sets the volume of mixture admitted to the cylinder(s) which directly corresponds to the brake mean effective pressure that the piston(s) exerts on the crank. This is pretty closely matched to the shaft output torque.
There is a current limit on the Xiechang controllers, in fact both linear limiting and current peak shut off protection. The linear current limit mode effectively sets the maximum torque that the motor/controller will deliver, by reducing the commanded PWM duty cycle when the supply current exceeds the programmed level. In effect, this tends to give power limiting, as it fixes supply current (but not phase current) whilst allowing the motor current and voltage to change in accordance with the applied load.
Jeremy
JennyB
1 kW
Kepler said:
At those power levels you don't need a freewheeling crank, so the simplest solution might be a tongxin/cute on the down tube, chain driving the (hopefully redundant) 28t inner. A 12 tooth cog should give a brisk but usable cadence.
Can that be made to work on an unmodified chainset without the two chains rubbing against each other?
recumpence
1 GW
I can tell you light weight and performance can go together, but you have to really source things properly and mate ideal components together to achieve it.
My first electric bike is my Actionbent Midracer. That bike weighs 48 pounds with a 12S, 10ah pack. It runs 40mph on a fresh charge and averages 14wh per mile at 20mph without any pedalling at all. My Catrike 700 weighs 59 pounds (it is a trike, after all) and has the same battery capacity and efficiency as the Midracer, though a lower top speed. Both of these bikes pedal like a normal bike. There is very little discernable slowing from the weight while pedalling. I use both of them primarily as pedal bikes that give some accelleration help and hill climbing aid. Ridden that way, the batteries run a looooong time on a charge. In fact, I only recharge them once every few days when I am doing alot of pedalling.
I think the best way to go with these electric drives (for most people, anyway) is a light weight assist, not a motorcycle with pedals as an obligation for "Legality". For me, I want the exercise and the increased range that pedalling gives me.
Matt
My first electric bike is my Actionbent Midracer. That bike weighs 48 pounds with a 12S, 10ah pack. It runs 40mph on a fresh charge and averages 14wh per mile at 20mph without any pedalling at all. My Catrike 700 weighs 59 pounds (it is a trike, after all) and has the same battery capacity and efficiency as the Midracer, though a lower top speed. Both of these bikes pedal like a normal bike. There is very little discernable slowing from the weight while pedalling. I use both of them primarily as pedal bikes that give some accelleration help and hill climbing aid. Ridden that way, the batteries run a looooong time on a charge. In fact, I only recharge them once every few days when I am doing alot of pedalling.
I think the best way to go with these electric drives (for most people, anyway) is a light weight assist, not a motorcycle with pedals as an obligation for "Legality". For me, I want the exercise and the increased range that pedalling gives me.
Matt
Kepler
10 MW
jbond said:
No problems jb. I was a little out of line myself. My apologies and once again, welcome.
recumpence
1 GW
Kepler said:jbond said:
No problems jb. I was a little out of line myself. My apologies and once again, welcome.
Wow, you guys sure are appologetic to each other. Maybe I am a naturally insensitive individual or something, but, I never noticed anything offensive said by either of you.
Matt
Kepler
10 MW
Where all nice blokes here Matt Problem when we write stuff on forums, as you know, it can come across as agressive very easily even when you dont really mean too. Maybe i need to include more 
Problem when we write stuff on forums, as you know, it can come across as agressive very easily even when you dont really mean too. Maybe i need to include more 
sk8norcal
1 MW
IMO, in terms of practical cycling,
the assist is most needed for acceleration from stop,
in recreational cycling, hill climbing is part of the 'fun' of the ride..
the assist is most needed for acceleration from stop,
in recreational cycling, hill climbing is part of the 'fun' of the ride..
JennyB
1 kW
sk8norcal said:IMO, in terms of practical cycling,
the assist is most needed for acceleration from stop,
in recreational cycling, hill climbing is part of the 'fun' of the ride..
Depends on where you are riding. In any case, both starts and hills are acceleration, which is the main range limiter. You can easily adjust your steady-state speed to match your capacity, but sooner or later circumstances call for one push too many, and that's when you blow.
I'm not convinced that low power assist is necessarily the most economical way to go for range in the real world, if you are also trying to maintain a good average speed.
Assume you have a low power system that assists you to an average of 20 mph, but 5% of your ride is hills that pull your average for that section to below 10mph. To complete the whole on time, you need to ride the remainder at just over 21 mph. Not much of a speed difference, but it requires about 14% more power.
A single-speed system with enough power to maintain 20 mph over the toughest section would need over twice as much power, but it is only using it for 2.5% of the time. Because it can afford to go slower the rest of the time, it saves 3 times that investment.
Hillhater
100 TW
Not every cyclist is as capable as L Armstrong.sk8norcal said:IMO, in terms of practical cycling,
the assist is most needed for acceleration from stop,
in recreational cycling, hill climbing is part of the 'fun' of the ride..
for some folks, cycling is not for fun, but for transport, either necessity or convenience, and hills are definitely not fun to many of those "practical" cyclists.
.. and to some, hills are a serious barrier to any of the other advantages that cycling may have.
Electric assist for commuting is the best thing since sliced bread. No, it's better. I can't describe how nice it is to have electric power when you are commuting.
I'm a roadie/racer, and also love pushing my physical limits, but not when going to a restaurant to meet a friend, or work.
And it is totally fun to go up steep hills at 15mph with casual effort. Of course, with any ebike, it does take away the 'physical accomplishment' feeling.....but I don't lack that - that's what the road bike is for.
I'm a roadie/racer, and also love pushing my physical limits, but not when going to a restaurant to meet a friend, or work.
And it is totally fun to go up steep hills at 15mph with casual effort. Of course, with any ebike, it does take away the 'physical accomplishment' feeling.....but I don't lack that - that's what the road bike is for.
sk8norcal
1 MW
JennyB said:
Definitely, but I get the feeling that most "practical" cycling done by majority of cyclists are on the flats.
I believe most cities are not on hilly terrain.
(I believe even in SF, you can manage to get around most places by avoiding hilly terrain)
I live in Silicon Valley, pretty flat here...
Hillhater
100 TW
Miles said:
ditto for Sydney. My residential area is officially called "The Hills District" ! ....for a good reason.
If you check with google Earth, you will see that northern Sydney is nothing more than a complex series of ravines, hills, and gorges . Many of us have rock cliffs in our back garden.
sk8norcal
1 MW
i think someone should do a study of the market for practical cycling,
my bet is hill assist usage will be secondary vs stop/go riding.
the more congested area, more stop/go...
my bet is hill assist usage will be secondary vs stop/go riding.
the more congested area, more stop/go...
drifter
10 W
Some of us are aged 60+ and in my situation having electric assist to help me uphills or just to get back home makes the difference whether I cycle or not.
Hillhater
100 TW
+1 Drifter. Exactly how i was thinking.
Solcar
10 kW
While there are lots of places where there are many hills, often steep, there are places like plains that might have a lot of wind. In that case it is nice to have assist to help push against strong headwinds.
sk8norcal
1 MW
drifter said:
I don't think that a low weight, minimal assist system would be for you then,
you would want something with with more power and range...
miles said:
why not?
I would bet most electric bike usage are done on the flats,
I used to be really into cycling and commuted for a while (cause I just wouldn't have enough time to train after work)
15 miles each way, I actually drive 5 miles to the start of my ride...
if I could get rid of all the re-acceleration effort from stop, I could increase my range..
Similar threads
