about electric motors

Discussion in 'Electric Bicycles' started by jucasan, Jan 14, 2011.

  1. jucasan

    jucasan New Member

    I'm thinking about making my 1st electric bike but still a bit lost. I was looking online and I was reading about regenerative braking and regenerative motors. Are these the same thing or there is a difference?

  2. DuctTapedGoat

    DuctTapedGoat Active Member

    I don't know jack about electrics, I'll put that out right now.

    Common sense will tell me that the difference is this.

    Regenerative Braking - Battery charges when you brake.
    Regenerative Motors - Battery charges when you ride.

    The noticeable differences are these.

    Regenerative Braking Motor - You will have a faster speed, more torque, but your battery won't last as long as a full on Regenerative Motor.

    Regenerative Motor - You won't have as much speed or torque, but your battery will last longer as some of all the power exterted will go back into the battery.

    Now, keeping in mind I don't know jack about electrics, that's all opinion based on reasoning.

    Please, someone correct me if I'm wrong.
  3. retromike3

    retromike3 Member

    a question about power

    The main reason I decided to forgo the electric mode is that it is impossible to get the the same power out of even the best electric system than you can out of a gasoline engine. my little half a gallon gas tank will get me over fifty miles at about forty miles an hour.(I don't have a speedometer so I don't really know how fast I am going officer) and even at three dollars a gallon it is still much less expensive than the bus.

    electric is much more quiet and smooth and better for the environment but unless it can get me there quickly and when I want to it will remain a unfulfilled dream.

    Mike Frye
  4. Ypedal

    Ypedal Member

    In general, electrics are good for 20 miles or less.. if you have to go much longer than this you get into special setups and more expense.. certainly possible but not always economical... i've build a 100 km range ebike.... but i never go that far so it was a waste with excess weight i did not need..

    Regen.... bottom line is that ebikes are not heavy enough to make it worth while, you can only generate so much energy from a system and it's a factor of how steep the hill is and how much weight you are trying to slow down...

    It's "generally" accepted that you are better off coasting/freewheeling down hills than trying to recouperate that energy..

    There is possibility of using the motor ( only direct drive hub motors need apply, as geared setups freewheel and canot force the motor to spin and generate energy) as an E-brake, turning the motor into an anti-lock braking system to save on brake pads but again, unless you have to go down a reallllly big hill at a reduced speed, it's not worth it.

    Cars, EV, on the other hand, have alot more weight, and can generate more energy in the process .. but ebikes benefit from simplicity and less weight.

    Also, be aware that regen can in some situations damage your battery pack, if you head down a big hill from a full charge, you risk over-charging your pack and frying it.. complex electronics can prevent this, but again it's not an off the shelf options at this point in time.
  5. jucasan

    jucasan New Member

    still confuse

    Is this true? Probably a regenerative motor is more atractive than a regenerative brake to me
  6. Ypedal

    Ypedal Member

    There seems to be some confusions regarding terminology here.....

    All electric motors can create energy by being forced to turn, mechanically, or can be fed energy from a battery to make it turn..

    example, the alternator in your car is an electric motor, the gas motor is forcing it to spin at X rpm creating a certain voltage that recharges your 12v lead acid battery in the process...

    In the same way, a direct drive hub motor, powered by a battery and controller, has a max rpm depending on the voltage of the battery.

    More voltage = higher rpm

    So lets say that a bike with a hub motor on 36v goes 20mph on the flats at full throttle... you keep the throttle on full and roll down a big hill where the bike goes over 20mph, by going down the hill faster than the max rpm of the motor at 36 battery volts, the motor generates higher voltage because it's forced to spin faster by the hill and your momentum, at a certain point you will be producing energy from the motor that can be fed back into the battery and increase the battery voltage and put energy back into the pack...

    That exists right now with most hub systems... right out of the box.


    With the right electronics, you can rig a switch that disconects the battery from the controller, and makes use of the energy produced by the motor while on the downhill right down to 0 rpm and you can do one of 2 things with this energy, either run it thru a big resistor to turn it into heat ( Resistive Braking ) or feed it into electronics that can step up the voltage and feed the battery pack ( Regenerative Braking )

    confused yet ? :eek:

    All that said, unless you roll up and down severe mountains, most places on earth will not produce any meaningfull enery from all this, it can be usefull to bring you to a stop saving on brake pads, but regen to charge your battery pack typically only delivers a few small percent points back of usable power because you have to factor in the losses in those electronics on top of the added weight and complexity of the system....... just not worth it right now until someone makes a plug and play solution for it and i don't know of any readily available right now.

    I have had the opertunity to ride Justin L's ( ebikes.ca ) ebike that he crossed canada with, something like 6000 kms for 8$ of electricity ( he left vancouver BC, and i'm in Moncton NB, so coast to coast ) .. he made his own controller, it has means of using the throttle as a variable adjust braking system, you pull a brake lever attached to a wire ( not a brake cable, but an electric wire ) that turns the throttle into a brake lever by causing resistance in the motor according to how much you twist.... really cool and very smooth !!!
    Last edited: Jan 15, 2011
  7. DuctTapedGoat

    DuctTapedGoat Active Member

    Not confusing at all - resistive braking makes a lot more sense, and I really dig that about the variable brake on the throttle!
  8. jucasan

    jucasan New Member

    Thanks Ypedal, now I'm starting to understand a bit more about this. Now, what is the function of the controller?
  9. Ypedal

    Ypedal Member

    An ebike Controller is the Electrical equivalent of a Carburetor .

    It allows you to use a throttle to regulate the power going to the motor.

    A Brushed motor does not really need a controller, it can technically just have an ON/OFF switch, there are only 2 wires that exit the motor, + and -

    A Brushless motor has no brushes, and wired in such a way that there are 3 power wires that exit. ie: 3 phase. The controller needs to time 2 of the 3 wires at a time in a certain pattern to push or pull a magnetic field inside the motor.. Most motors also have 5 more tiny gauge wires going to three hall sensors inside. These tell the controller if the copper coils have a North or a South magnet facing them, this is essential for a powerfull Instant Start brushless setup. Some motors and controllers only use the 3 power wires and disregard the hall sensors ( Sensorless ), some requrie that you pedal first to get the magnets spinning, other controllers can use software to bump the motor and take off from there, sensorless is not ideal at a dead stop and sometimes fails to start if the motor is heavily loaded.

    Everyone has played with magnets, North and North push eachother, N and South attact... well the magnets in a Brushless motor are in a ring of N-S-N-S-N-S so if you time a positive or negative flow of electricityy thru a copper coil, it will either push or pull against the magnet facing it.. causing it to spin.

    The throttle does not vary the voltage to the motor, the motor always sees the same voltage, but to make the motor turn slower at partial throttle, the controller turns the power on and off very quickly ( Pulse Width Modulation, often PWM seen on controller pages ) ..

    Most controllers have a " Max Amp " rating, regardless of the voltage you plug into it, so if you run a 20 amp controller at 36v you get peak 20x(batt operating voltage that varies depending on battery type ) but on a fresh charge 20a x 40v = 800w peak

    Take the same controller and put 48v to it and you get 20a x 55v = 1100w peak

    Once you reach cruising speed, the controller usually does not have to limit the amps anymore, it just lets the motor draw as many watts as it needs to keep the speed constant, at 20mph that is usually 200 to 300w .. at 30mph that goes up because of wind resistance so 500 to 700w ... notice almost double the power for 10 more mph !!

    ugh.. ES is offline with upgrades going on.. i'm loosing my mind ... information junkie the internet turns you into lol..
    Last edited: Jan 16, 2011
  10. wheelbender6

    wheelbender6 Well-Known Member

    Locomotives use the Resistive Braking to save brake wear. While going downhill, the current from the motor is fed to resisters and escapes as heat, just as Ypedal described.
  11. richardmg9

    richardmg9 New Member


    Regenerative braking usually requires a hub motor, as most chain drive setups do not transfer power from the wheels to the motor(or your peddles). There is no regenerative riding, only braking. If you peddle against the braking, or have a gas engine work against it, or you are motor braking down a hill, that would be "regenerative riding", but it's all braking. Also, anyone who says electric is slow is misinformed. http://www.youtube.com/watch?v=WKAMus3oSdw Granted, that is an expensive setup, but brushless motors with lipo batteries can be faster than gas. One last thing, electric motors do NOT make max torque at stall, however they do make max torque early in the rpm range. And one last nice rule of thumb I like, an average person peddling makes 250 watts.
  12. sangesf

    sangesf New Member

    The only thing that gas has over electricity is the initial cost is lower..
    However, over time, the electric bike is cheaper.
    My current setup allows for 80miles distance @ 20mph.
    Any faster or longer distance, buy a motorcycle...
    My cost is ~$1500 for the bike.. Yes, it takes 3 hours to "refuel" from "empty" but trust me, after 80miles you NEED the rest.
  13. retromike3

    retromike3 Member

    I hate to disagree ,But

    The main problem with electric powered bikes is the fact you just can't store that much energy in a conventional battery as to the chemical power in gasoline. Granted that they do make high storage low weight batteries for laptops and cel phones,but even they are not even close to the power per weight of a ounce of gasoline.

    I looked up electric bike when I first was looking at getting a commuter going. The best thing I could find would not serve my needs. Motor bicycles are noisy,they rattle,they smoke and pollute, but they have the ability to go a long way at a reasonable speed for a reasonable cost.

  14. Happy Valley

    Happy Valley Active Member

    I'm running ICE powered bikes but those kind of performance numbers are certainly getting into the ballpark for me with an electric.

    As to cost, after toying with an HT engine some years back I moved on and come to know decent gas powered bikes/engine set-ups are gonna run a $1000 anyway so your number on that is not out of line. Good news!
  15. etard

    etard New Member

    As exhibited at the Tuscon Death Race, electric technology is overtaking ICE power with great momentum. Using the electric push in RC aircraft as a catalyst, many homebuilders are seeing much greater gains I'm power and torque than even the 2 strikers can reproduce. Paul's bike was putting out 4.5 hp, but with the linear torque curve of the electric motor, he was able to accelerate as fast as Alex on his 10 hp Morini. He also had about a 25-35 mile range and his bike only weighed about 50 lbs. He can then recharge in about an hour or two and only spend about $.10. If one was a fabricator, he could reproduce Paul's setup for less than $1500. His ride was also fairly conservatively run, he could probably pump 2 or 3 more horsepower through his system before things began to break.

    I love the motored bikes, especially te old flat tracker style, but electric will always win out when you need a little peace and quiet.
  16. retromike3

    retromike3 Member

    peace and quiet

    Your right about peace and quiet. the bike will not make a sound while you are waiting for the battery to charge. How many hours is another matter. As for the range of the bike, my little motorbicycle will go about thirty eight miles an hour for about sixty miles on a tank(half gallon of super)

    Granted all of the other problems I brought up with internal combustion are true. But its still a grate way to store a huge amount of energy. And yes I know that most of the energy that you expend when you burn gas actually goes out the tail pipe in the form of wasted heat.

  17. Skipper Dan

    Skipper Dan New Member

    I am about to get a system going with an electric motor. I am going to use a 24v brushless here: motor http://www.alibaba.com/product-gs/266907604/electric_tricycle_motor.html or something similar. should draw around 15 amps. at 12v or 9 amp at 24v. That is only a guess on my part. I am gearing it to go 20 mph max. 12v battery has around 100 amp hours. 100/15=6.6 or 6.5 hours. 6.5 * 20mph = 130 miles 100/9=11 11*20=220 miles.

    Cut that number in two for battery sake gives 65 and 110 miles as a minimum and pedaling also would give better results. Am I way off base here.

    I know the batteries are draining faster than the 20 hr rate but stop and go traffic so it is not constant. Who can ride for six hours without stopping anyway. I think the speed is going to be a lot slower 20 mph is rather fast for in between stop lights.

  18. sangesf

    sangesf New Member

    A 12v 100AH battery is going to weigh about 60lbs and the motor is going to pull more like 40a at 12v, and the usable ah of the battery is 60ah, so figure 1.25h running at 20mph = 30miles actual.
  19. Skipper Dan

    Skipper Dan New Member

    how are you doing this 80 miles with only a 20ah battery?
  20. etard

    etard New Member

    Besides that, can you think of anywhere on your bike you would want yo strap a 60# battery that is at least 8 inches wide? You're gonna fry that motor at 12 volts too. I appreciate your enthusiasm, I was the same way when I wanted to build my first bike. Try this website:


    A lot of good information for consideration here.

    The easiest way to get into ebikes is with a Hub motor. You should be able to get a full kit sans batteries for about $250. If you are interested, pm me and I will send you a link.