250W vs 500W

[partymarty]

If I can get 40 km pedal assisted out of my 500W motor does this mean I would get 80 km from a 250W motor with the same battery? Thx

 

[deardancer3]

Not really.

For example, lets say your route only demanded 200watts for most of the terain/speed. then your 500w motor and your 200w guy would have real close to the same range with identical batteries, adjusting for inefficiencies of course.

And this is reality, since unless doing very demanding riding, most riding is well under a 300w load.

d

 

[Lessss]

No, it means your batteries/controller/motor are likely to have a longer life as you are pulling less amps. Distance may be greater but not double.

 

[torker]

Theoretically yes.But not quite. Also if you have a cycle analyst or a controller that you can control the amperage then you could just reduce the amperage by half on the 500 w motor and do the same thing. Like Lessss says though you may not double your range. Any motor is most effeiciant at max rpm so running it slower will not be as good.

 

[partymarty]

Thanks guys. What is the difference between 24v and 36 v? Speed?

 

[Drunkskunk]

Flat No.

The rating on the motor is missleading. its a rating of how much power it will draw at a given voltage under a given load. Those are almost never specified, and in some cases, the 250watt motor and the 500watt motor might be the exact same motor, being labled for diffrent markets.
generaly, however, the high watt rating means a bigger motor than can handle more power without overheating.

But thats a little off topic. Specific to your question, it takes the same amount of power to go a certian speed and distance, regardless of motor. it might take you 200 watts to go 20kph, and 400Watt hours to go 40km. That rating is the energy needed to move you, regardless of the motor. the only diffrence the motors will make is in efficancy.
All things being equil, there won't be any diffrence in efficancy on the motors. in reality, the bigger motor may (depending on what the controller allows) accelerate faster (it also may not) and use more power on acceleration. it might also weigh more and cost a little more power to get up a hill. call it 1%. maybe. So in that case, if you could go 40km on the 500 watt motor, you might, maybe, possably be able to go 40.4km on the 250watt. maybe.
Then again, maybe not. the efficancy diffrence between two identicle motor off the assembly line is probably higher than the amount of diffrence between running a larger or smaller motor.

 

[Drunkskunk]

Thanks guys. What is the difference between 24v and 36 v? Speed?

Speed, and power.
if the amp limit is the same, higher voltage means higher wattage available for the motor, so more torque and better acceleration too.

 

[dogman dan]

It generally works better in more different conditions to get the 500 watt bike and then ride it using only 2 or 300 watts if you want better range. In other words, ride slower, increasing the percentage of the total wattage being provided by your legs. Pedal harder at any speed. With my big front sprocket, when I feel frisky I can pedal real hard and really lower the amps the motor is using while still riding 25 mph. Most ebikes hit a point where full throttle is faster than the pedals can keep up with, but that problem can be solved as I did.

But if you choose the 250 watt, and run into difficult conditions, your are simply screwed. It happend to me last night, on a run to the Auto parts store for some 12 guage wire. When I left the house it was breezy, but not that bad. But on the way home, a nearby thunderstorm blessed me with 45 mph winds with 60 mph gusts. The 350 watt bike I was on pretty much choked on it, and could barely move at 10 mph. Shoulda took the 1000 watt bike that trip.

 

[dogman dan]

I should have pointed out though, you want to have a motor and controller sized to fit the capabilities of the battery you intend to use. So if the amp rate of 250 watts is all the battery can stand without dying prematurely, then the 250 watt is the one. Bigger wattage motors and controllers , like 1000 watts on up, put tremendous strains on a battery intended for a 500 watt bike, for instance.

A few genrealizations. A 10 amp hour battery of most chemistries is fine with motors in the 250 watt-400 watt range At 500 watts to 700 watts, 15 amp hour to 20 amp hour batteries may be a good size. This is for " affordable" lifepo4, nicad, nimh, slas. The expensive lifepo4 can put out a lot more amps. So if you are looking at pretty affordable motor kits with 10 ah batteries, a 250 watt kit using 36v will be easier on the batteries than a 500 watt kit.

For higher wattage motors, higher voltages help with power and top speed, and maybe range. The same motor with a 36v 10 ah battery will be slower than the 48v 10 ah battery. In addition, the 48v battery will be simply larger, and have more avaliable watthours of electricity inside, and should be able to take the bike farther than the 36v one. The 48v one will be 25% heavier, since it's 25% bigger. The higher voltage of the 48v version will mean more watts avaliable to the motor if the amp rate is the same for both.

 

[Russell]

I run my "250W" geared motor on 48V (54V peak) and pull around 750W peak. I run my "500W" DD motor on 36V (41V peak) and pull a maximum of 600W. Both controllers are 15A and both bikes will run around 23.5 MPH on the flats when fully charged. Each motor consumes nearly the same amount of power when ridden over similar terrain under the same conditions at the same speed.

 

[icecube57]

I thought the numbers also meant that the motor is designed to take X amount of watts almost indefintely without overheating. But then in again in GM case they change the controller to a higher amp one... they all of a sudden discovered a new motor line. Also at cruising top speed my gm 48v 1000w motor consumed about 1000w and peak at 16-1800w under acceleration a 35A controller. With a 20A controller the results would be different. Motor ratings are hog wash i think.

 

[DahonElectric]

If I can get 40 km pedal assisted out of my 500W motor does this mean I would get 80 km from a 250W motor with the same battery? Thx

Yes for the Bionx system against my 9C system. Over the same terrain, I could only get about 70-80km with my Bionx, whereas 40km was the max I could get out of my 36V NiCAD 9C system. And don't forget, the 9C is on a 700c wheel, whereas the Bionx is on my Dahon folder which is a 406 wheel (20 inch), which spins a lot more to complete the same distance.

I can explain this problem. With all non-Bionx system, you can not pedal efficiency with it period, unless you have an eZee system which is allows freewheeling when the motor is not used, but even that it is still not as efficient as a Bionx. Secondly, 400w or 500w simply means that the output power of the motor is exceeding that of Mr. Lance Armstrong or Alberto Contador. Unless you are one of them or better yet, much more powerful that the current TDF champion, you will not be able to help the motor conserve power unless you have the ability to manually sense the pedal power output of yourself, then adjust the motor to simply complement the additional needed power -- aka strain gauge or Power Tap (power meter). A human being is simple not capable to do this. So, if you want the equivalent of a Bionx system, you have to install a $1000 PowerTap rear wheel, then use the Cycle Analyst to complement your pedal power. So the best I could do with my 9C system without a Power Tap wheel is do a "Pulse and Glide" which sucks a lot of juice from the battery because everytime you pulse, you are sucking lots of amps to overcome inertia (your bike slowing down). Even then, it simply doesn't feel right. So, I just "fake" pedal, perhaps contributing only to about 50watts max. Besides, my fingers get really tired variably adjusting the throttle to match my pedal strokes over a varied terrain anyhow. Not so with the Bionx.

In fact, a month ago, I met a guy on a hand cycle (he's wheelchair bound) and he has the Bionx system installed (36V Lithium system). Toured with it towing a trailer over 100km with 2 batteries and had spare juice left to spare!

If you really like to pedal full time and feel like you are doing some cardio work, the Bionx is it. After since I used the 9C full time, I didn't realize that I had lost quite a bit of cycling fitness. Well, I'm back with the Bionx now and only use the 9C as a non-pedal ebike.

Last but not least, the difference between a 24V and the 36V is simply speed. When you are depleting the battery energy, the voltage drops. 36V has quite a ways to drop to 20V, whereas 24V doesn't have much. In terms of max speed, my 36V 9C can go up to 40km/h fully charged and slightly assisted, whereas my Bionx 24V can go up to 32km/h pedal assisted.

Hope this helps..

DE.

 

[dogman dan]

It did take me about 2000 miles of commuting before I even began to get the hang of riding more efficient, where a bionx would have done it in the first mile. I had to get into a lot better shape too, for my pedal effort to make any difference in range. Riding slower is easier said than done too, with the throttle easier to hold in one spot at full throttle, it tends to creep up to there over and over. I find that sometimes I need to just select a lower gear to keep from creeping up on the speed when I want to hypermile. Then keep to a speed that keeps you needing to push that lower gear. It definitely takes practice to get the hang of.

 

[fifthmass]

It definetly takes time, lots of miles, AND a watt-meter to learn how to effectively match manual throttle input to to terrain and speed/cardio effort desired.

When I first got my ebike in November of last year I was using 17-20 wh/mile riding around Boston. Used lot of power for startup and acceleration but was pedaling full time. At the present I'm using only 10-11 wh/mile for the same rides with the same average speeds. I am in better shape now (30 lbs lost weight) and am probably pedaling a bit harder but my throttle control is second nature now and IMO much more efficient.

The Bionx would be more efficient still but it just seems too 'cruise control' for me.

Ride safe,
Bill

 

[Russell]

I can explain this problem. With all non-Bionx system, you can not pedal efficiency with it period, unless you have an eZee system which is allows freewheeling when the motor is not used, but even that it is still not as efficient as a Bionx. DE.

Not true...oh so not true. If you want to ride with maximum efficiency on an ebike, any ebike, you can certainly do so. I have a combined 2,400 miles on my two ebikes just this season and I ride them very efficiently. What it takes to do this is a light touch on the throttle (I use modified trigger throttles), keep speeds close to your natural ability on a particular bike, monitor the power with a meter and pedal continuously. Doing this I use between 6 and 10Wh/mi to average in the high 16 to low 18 MPH range over the entire trip which is normally 20-32 miles.

I ride for exercise and figure I contribute about 50-60% of the total energy during my rides. I get a good workout but avoid the extreme peak exertion levels I used to hit on a conventional bike. For a commuter who wants to make better time and doesn't want to sweat efficiency numbers like I get aren't going to be possible. If you want to input 75W and average 20+ MPH you're gonna use a lot of juice.

-R

 

[partymarty]

I get 40km (24miles) on a 36v 7ah SLA and BL36. Am I efficient? Since the SLA is actually 4ah because of the Peukert effect (ebikes.ca), should I get 3 times this range with a 12ah lithium?

 

[Russell]

Yes very good, around 6Wh/mile, though you did forget to mention the average trip speed. And yes a good lithium battery will deliver 100% of its rated capacity however for longevity you'd want to keep actual consumption to 80%.

-R

 

[partymarty]

I average 20km/hr - it's my pedalling speed. I hit the juice on hills and for passing tourists.

 

[deardancer3]

If I can get 40 km pedal assisted out of my 500W motor does this mean I would get 80 km from a 250W motor with the same battery? Thx

Sooo Marty, do you have the information you were looking for? I presume you were looking to increase your range, and hopefully you found that a good Amp meter and a well adjusted/tuned bike and rider will do more for that than downsizing your motor. And a bigger and more capable battery. Meanwhile we debate other pieces of ... hmmm information.



d

 

[partymarty]

If I can get 40 km pedal assisted out of my 500W motor does this mean I would get 80 km from a 250W motor with the same battery? Thx

Sooo Marty, do you have the information you were looking for? I presume you were looking to increase your range, and hopefully you found that a good Amp meter and a well adjusted/tuned bike and rider will do more for that than downsizing your motor. And a bigger and more capable battery. Meanwhile we debate other pieces of ... hmmm information.



d

I am fine with my 7ah piece of junk since I never go more then 40km. It's my sister that wants an e-bike so she can accompany her husband "Lance" on his 200k day rides. It looks like if she rides like me she will need 25ah which is expensive and heavy... but she's paying! Thanks everyone.

 

[DahonElectric]

Many of you are absolutely right. You can definitely ride a long distance with an ebike without the Bionx's strain gauge and be able to stretch the battery a long way. After all, how much does my 9C and battery system adds up? Hmm a mere 40lbs or so. No big deal since I've toured with an 80lbs + load myself averaging at around 20-22km/h over a max distance of 100 miles or even longer. So does it mean that my 9C can travel up to 100 miles with battery juice to spare? I can certainly ride my Bionx 100 miles with my 250w system and do a credit card tour still have a lot of juice left. I simply dial the assist to "0". The only problem with direct drive systems is that, it doesn't freewheel all that much. I've ridden the eZee system and I think that's a great system and in fact, should have bought that instead!

I also think there's a misconception on how a Bionx system works. There's an assumption that the pedal and power assist combination is what a Bionx system does. As a matter of fact, it provides power assist based on the rider's power output and riding style. And this is based on gearing and the Bionx system adds the appropriate additional power based on the assist level you programmed onto the console. Which means, the rider always has command of his or her gearing selection at ALL TIMES regardless of terrain and the rider can always maintain normal regular cadence. I usually ride around 95 to 100 rpm (I'm a spinner). I find it quite difficult to spin 100rpm with a powerful motor and variably tune the throttle to match my power output on the 9C. It became tiring after awhile, so I ended up using it fully assisted. Or I simply ride it like a normal bike and then use assist going up a hill.

A human being does not have an unlimited fuel source. We store fuel in our muscles (muscle glycogen) and liver (liver glycogen). When we pedal, we use them, but this is expended in a rate controlled in part by which zone we exercise in. Usually, if we want to do endurance sport, we want to be in lower to medium aerobic zone which allows us to burn equal proportions of fat and carbohydrates. No doubt people are getting fit on ebikes and thanks in part to this. Let's say one rider's efficient easy aerobic zone would be around 150watts and am able to ride long, the only way to maintain a lower heart rate is to switch gears to maintain steady effort. If you are able to ride only with 100 watts and the computer provides 50 additional watts and can do so automatically, accurately and consistently in ALL GEARS and in all terrain, wouldn't that mean a rider will ride even more efficiently at the same speed? The answer is yes. If the battery can help the rider conserve his or her riding energy, wouldn't that also help the battery back in return. Many of you had done that, but what is different in a Bionx system is that, it is done so automatically and in all riding gears. It's definitely not cruise control, because the assist level is based on what you put in. You put in lesser, it puts out less (not more). You do not need to match your gear to the motor. The motor matches your needs. I've re-programmed the Bionx to show energy consumption and prediction based on approximate riding efficiency, simply meaning what the computer thinks I can cruise out to. At one time, I got a number of around 225km, based on my 150w riding output. Btw, that 80km ride I did last year was based on an average speed of 18 miles and 2 hills with a gradient of 8% with the Bionx. So a strong fit rider can really benefit from this system and so did the hand cycle dude with his PL-350.

If someone designs an interface with a heart rate monitor to control the motor speed to ensure the rider stays at the designated heart rate, now that would be interesting!! Include that as part of the Cycle Analyst upgrade and yeah, I'll be the first in line to buy it -- hint hint!!

DE.

 

[DahonElectric]

I get 40km (24miles) on a 36v 7ah SLA and BL36. Am I efficient? Since the SLA is actually 4ah because of the Peukert effect (ebikes.ca), should I get 3 times this range with a 12ah lithium?

Actually marty, the 36V Nicad ebikes.ca is selling is a pretty good replacement battery for your SLA. Not quite lithium, but not very heavy either and I quite like it. I get about 40k with it with little pedaling -- you figure it out the math. Nothing suck up more amps than going up a steep hill, unless you're willing to sweat it out. But that's not the point of riding an ebike right!

DE.

 

[dogman dan]

To keep up with a roadie, on looong training rides will take a very big battery. Good roadies can ride away from me on my 350 watt bike that goes 20 mph. So your sister may not ride near as efficient as you do Marty. BTW, you are very very efficient. She needs to look at perhaps two 48v 15 ah Pingbattery lifepo4's. That would give her about 40 miles of range at 30 mph. More of course, if the training rides are slower, like 18 mph. Any more battery than that, is simply too heavy to carry easily. The two pings and the boxes for them will be about 40 lbs.

I agree with Dahon about the Bionx, though I've never ridden one. It took me 2000 miles of riding to even begin to ride my ordinary motor better. Too bad the bionx has such a fussy battery arrangement. One of those, with 30 ah would be ideal for your sister.

 

[Russell]

Many of you are absolutely right. You can definitely ride a long distance with an ebike without the Bionx's strain gauge and be able to stretch the battery a long way. After all, how much does my 9C and battery system adds up? Hmm a mere 40lbs or so. No big deal since I've toured with an 80lbs + load myself averaging at around 20-22km/h over a max distance of 100 miles or even longer. So does it mean that my 9C can travel up to 100 miles with battery juice to spare? I can certainly ride my Bionx 100 miles with my 250w system and do a credit card tour still have a lot of juice left. I simply dial the assist to "0". The only problem with direct drive systems is that, it doesn't freewheel all that much. I've ridden the eZee system and I think that's a great system and in fact, should have bought that instead! .

I use the throttle about 90% of the time I'm riding so my efficiency numbers aren't due to riding without assist for long distances, if I wanted to do that I'd ride my regular bike. Power consumption is all about speed pure and simple. If you want to ride a lot faster than you can ride unassisted then you're gonna use a lot more power than someone who uses a motor for a little boost.

I have a Bafang, which is like a mini-eZee at a fraction of the cost. At 36V the Bafang is a nice little assist motor and at 48V it's a kick. I also have a front 9C and find the cogging torque to be of minimal concern. As I said above I'm on the throttle 90% of the time so what cogging torque there is with the 9C is essentially cancelled out most of the time. Both the Bafang at 48V and the 9C at 36V are pretty much an even match-up in speed, hill-climbing and total weight. In regard to the original theme of this thread the fact that one is a "250W" motor and the other a "500W" motor makes no difference in the range I get. I don't push either very hard however so neither of my motors or the controllers get very warm. I prefer the Bafang (at 48V) because I prefer riding the Kona Smoke over the Raleigh and I like the stealthier look of the Bafang.

I also think there's a misconception on how a Bionx system works. There's an assumption that the pedal and power assist combination is what a Bionx system does. As a matter of fact, it provides power assist based on the rider's power output and riding style. And this is based on gearing and the Bionx system adds the appropriate additional power based on the assist level you programmed onto the console. Which means, the rider always has command of his or her gearing selection at ALL TIMES regardless of terrain and the rider can always maintain normal regular cadence. I usually ride around 95 to 100 rpm (I'm a spinner). I find it quite difficult to spin 100rpm with a powerful motor and variably tune the throttle to match my power output on the 9C. It became tiring after awhile, so I ended up using it fully assisted. Or I simply ride it like a normal bike and then use assist going up a hill. .

I think most folks are well aware of how a BionX works. The BionX system is the kit I thought about buying years ago when I first considered electrifying one of my bikes.

I had the same control problem with the 9C as you when I first tried it. My first ebike conversion used a 36V Bafang with SLA batteries which had a top speed of around 16.5 mph. The output was well matched to my normal riding speed which made throttle control easy. The 9C however was a beast by comparison with a top speed around 23.5 mph. I found it difficult to ride with the motor simply assisting me as I had done with the Bafang, instead I found I was trying to keep up with the motor. After a few rides I did get the hang of it but it was a chore riding in the 16-17 mph average speed range as I had done with the Bafang. What I did to alleviate this problem was to change the resistors used to modify my trigger throttle to give me more low speed resolution. After that it was more pleasant riding with the 9C. The throttle modification was also helpful when I moved to 48V with the Bafang which made it a match for the 9C at 36V. I spin in the same range as you do and have no problem getting just the right amount of power with either motor but again I think it's due mostly to my throttle.

A human being does not have an unlimited fuel source. We store fuel in our muscles (muscle glycogen) and liver (liver glycogen). When we pedal, we use them, but this is expended in a rate controlled in part by which zone we exercise in. Usually, if we want to do endurance sport, we want to be in lower to medium aerobic zone which allows us to burn equal proportions of fat and carbohydrates. No doubt people are getting fit on ebikes and thanks in part to this. Let's say one rider's efficient easy aerobic zone would be around 150watts and am able to ride long, the only way to maintain a lower heart rate is to switch gears to maintain steady effort. If you are able to ride only with 100 watts and the computer provides 50 additional watts and can do so automatically, accurately and consistently in ALL GEARS and in all terrain, wouldn't that mean a rider will ride even more efficiently at the same speed? The answer is yes. If the battery can help the rider conserve his or her riding energy, wouldn't that also help the battery back in return. Many of you had done that, but what is different in a Bionx system is that, it is done so automatically and in all riding gears. It's definitely not cruise control, because the assist level is based on what you put in. You put in lesser, it puts out less (not more). You do not need to match your gear to the motor. The motor matches your needs. I've re-programmed the Bionx to show energy consumption and prediction based on approximate riding efficiency, simply meaning what the computer thinks I can cruise out to. At one time, I got a number of around 225km, based on my 150w riding output. Btw, that 80km ride I did last year was based on an average speed of 18 miles and 2 hills with a gradient of 8% with the Bionx. So a strong fit rider can really benefit from this system and so did the hand cycle dude with his PL-350.
.

I don’t think anyone will argue with you that the Bionx is not a good system however why many forgo purchasing a BionX is the high initial cost and the limited ability to customize the proprietary system. Cumulatively I probably have spent enough on ebike stuff that I could have purchased a BionX…but then I would not have had all of the fun. One day I may have to try a BionX but until then my brain will control the throttle based on feedback from my body to provide the right amount of power for any situation.

-R

 

[DahonElectric]

Hi Russell,

Ahhh okay.. I'm starting to see the light here with some of the confusion here. I suppose you do not own a Cycle Analyst?!? You do know that you can use the CA to do the throttle controlling for you automatically?

Did you know that the Cycle Analyst comes with a rudimentary cruise control function built into the box?? They call it the "limiting features" (page 12) and you also have the ability to tune the feedback loop of this cruise control to maintain the transition between on and off smoothly (page 13). So in effect, you can turn a rather dumb ebike into something similar to a Bionx system. It's actually pretty cool to feel the motor turning on and off, to maintain a fixed cruising speed with you pedaling with it the same time. I also limited the current draw too, so it climbs rather anemically without sucking a lot of amps (current limit feature on CA) and it helps conserve the battery usage quite a bit. Downside is that, it pretty much limits your bike to doing a certain speed. You need to restore those limits to higher values if you want the beast of the 9C to return and I find them tiring after doing a while. I much prefer Bionx assist 1 to 4 with a 1 button touch. I wish Justin would incorporate a "Cruise Control" function separate from the current limiting features and can only be engaged with a touch of a switch. The kill switch for this throttle on control would be the brake lever. JVBIKE sells the Bionx brake sensor.

Battery consumption is not a function of speed though. It's a function of acceleration and hill climbing and is controlled by the current draw of a set system, because once you achieve your cruising speed, current draw would be minimal right. Yes, you can somewhat control the throttle to minimize current draw, but if a computer does this for you like the Cycle Analyst or the Bionx, wouldn't that be even better?

I agree with you that the Bionx system is expensive and it doesn't have the guts to go head to head with more powerful motors out there, but I am actually looking into expanding the capacity of my Bionx system to include one of those LIFEPO4 24V 12ah battery ebike.ca has for sale. All I have to do is disable the regenerative braking so it doesn't charge the battery and then I'm set. Part of it is inspired from Denis who also owns the same bike as I do. But learning from his experience, I'm trying it on my out of warranty Bionx battery that I think is no longer 8ah -- probably closer to 6ah. Still 18ah in a nice light package is going to be cool!

Thanks for the reply Russ..

DE.