Nearly all retail electric bicycles and e bike conversion kits are listed at a specific power level like 500 Watt electric mountain bike or 250 watt e bike conversion kit, yet most of the time this power rating is misleading or just wrong. The manufacturers don’t use the same standards for naming their motors, and consumers don’t understand the difference.
Unit of Power is watt which is named after a Scottish engineer James Watt. Watt is used to measure the instantaneous power output of a machine like the electric motor on your e bike. Number of watts used by the electric motor is equal to the voltage supplied by a battery x the current flowing from the battery to the motor. Therefore and e bike motor connected to a 24 volt battery, supplied with 10 ampere of current would be powered at 24 * 10 which is equal to 240 watts.
So Here’s is How Fast Does an Electric Bike Go
So you see calculating the peak power of an e bike is just multiplying the voltage in the battery by the maximum current the bike can handle. This Maximum current is determined by e-bikes controller, and is somewhere between 15 to 30 amps. Bike with 48 volt battery and 20 ampere peak controller would be capable of 9 60 watts of instantaneous Power . This is where complications occur because the manufacturers of e-bike not always rate their parts this way.
General cause for this is skirt importation laws. A large number of European countries limit imports to e bikes with motor rated at 250 watt or less . 250 watts is not a good power for e bike standards.
Professional cyclists put more than 400 watts on leg power alone. So to clear their electric bike for import to many countries, e bike manufacturers rate the components much lower than what they are in reality on their e-bikes. This is very common in the industry as e bike with 250 watt Motors come standard with 36 volt
batteries and 15 or 20 amperes controllers. a 15 ampere controller means the peak power supplied to the motor is closer to 540 watts and a 20 ampere controller nearly over 700 watts.
How do the manufacturer’s get away with this? One method is to rate the motor for continuous power instead of peak power. Continuous power means a motor can handle safely power for an indefinite amount of time without any damage or any overheating. 250 watt continuous motor can run forever at 250 watts without overheating, but any more power will cause it to overheat, if a 250 watt motor is run at 251 watt will cause it overheat.
It is OK for ebike companies to rate their Motors this way if the numbers are accurate. But if a 250 watt continuous motor can handle more than 250 watts continuously this means the numerical naming is inaccurate and misleading.
The problem here is that it confuses customers and makes it much more difficult to compare different Motors.
How Can Power Ratings Be Used Best
While comparing e bike kits, first of all you should know if you are comparing continuous or peak power. When advised by someone that a 220lb Rider needs at least 1000 watt motor he means 1000 watts of peak power, the e bike should be able to produce the amount of power to drive the rider up a hill.
500 Watt ebike conversion kit listed as a 500 Watt kit, on inspecting closely shows that the kit comes with 48 volt battery and 20 ampere peak controller. This kit is capable of putting out 960 watts, essentially a 1000 watt kit. What initially appears to be too weak is actually a 1000 watt peak kit, perfect for 220 lb Rider.
When it comes to e bikes, 1 kilowatt, a full 1000 watts is just too big a unit. Generally e bikes are rated in un prefix words, with power ranging from 250 to about 900 Watts. If you think in terms of horse power, it’s about a third of a horse’s power to about 1.2 hp. Any bike with more power accelerates more quickly or carries more weight at speed up a hill.
What Do You Mean By Watts On An Ebike Actually?
To get some idea for what power means in human terms, we can see how many Watts a typical Rider uses on a standard bicycle. Just pedaling along at a cruising speed for a non sporting Rider takes 30 watts, it’s about the same energy as normal walking. Going up 220 mph, rapidly increasing Aerodynamic loads and 220 Watts is needed- most non athletes can sustain. Tour de France quality racers can put out 400 watts for an hour and somewhere over thousand watts on the short sprint to the finish of a race.
The other important concept is the energy related with E bikes. Power is related with acceleration but energy is related to range. In an automobile energy is stored in the form of gasoline and the car’s engine converts it into power. E-bikes are much more direct. The battery stores the energy and feeds it to the bikes electric motor to create power. Electric power units are watt hours, which means how many watts can be delivered for an hour by the battery. E bike batteries range from 300 watt hours to about 1000 watt hours. 1000 watt hours is expressed as one kilowatt hour.
As in cars, bike mileage varies. If you are able to calculate your range, the number of watts used per mile of travel is a more important number. Depending on the bike, your travel speed and how high the electric assist is turned up, the number that is somewhere between 10 and 20 watt hour per mile. It tells you that a small 300 watt hour battery may take you between 15 to 30 miles on an e bike. If you want to do long rides at a high boost level this may not be enough, and you have to get a bike with a bigger battery.
Most e bikes have a simple bar and percentage gauge indicating the state of their battery charge with which you will quickly get a feel of how far 10% or 25% of battery charge will carry you or how far you can go with no maths required. Unlike an E car, you can always pedal without assistance if misjudged and run out of battery.
Watt hour is a far more accurate way to know how much usable energy in a given pack battery pack is there, also translate it into how many Watts, continuously, for 1 hour! A 500 Watt hour battery can deliver 500 Watts for one hour or thousand watts for 30 minutes or 250 watts for 2 hours etc. A number of e bikes do not use power at an exact level, continuously, so it does not translate directly into ride time, but you can quickly see how a larger battery with more energy can deliver lower power for a longer time and go further on a charge.
Some of the vendors are prone to bending the truth and over promise in terms of range expectations. Do some research before you buy, ask the right questions and buy from a vendor that gives range estimates in relation to your weight, bike, intended use and intended input.
Ah vs Wh
It is very important to understand the difference between ampere hours and watt hours. Ampere hours means nothing unless you factor in the voltage and watt hour is more important because it factors in the voltage and ampere hours together and determines how far you might go on a full charge. All the packs are not labelled or constructed the same, so you have to be careful and you have to pay close attention.
A 48 volt battery with an extra 120 watt compared to a 36 volt pack will not always give you more range, if you are going faster than a 36 volt battery going at full throttle, but the more watt hour you have on the bike , the more range you can get from it.
With just a little knowledge, you can get better informed buying decisions, put together the proper kit and ride happily without running out of power and not buying a lot more than you need.
The common mistakes many ebikers make is to want a huge battery, this is fine until you have to find out how to mount it on your e bike and it gets worse when you carry it up a flight of stairs or put it on a bike rack.
You have to be realistic and you can save yourself from a lot of headaches and money, also you can end up with the best ride possible for your needs.
If the trip is a long one and if you can stop for a short break or coffee, plug in the charger and grab some power, it might not charge fully but it will extend your range if needed and in case anyone ask, electricity from the wall cost about 10 cents per kilowatt hour 360 watt hour battery pack of yours withhold less than 4 cents of power on a complete charge.
To conclude the 1000 watt is powerful and fast. It will take 190 lbs. man up any hill without pedaling easily. This is a great kit, cheaper and easy to install then buying a manufactured e bike and the most amazing part is that you can pick the bike. 1000 watt is highly recommended if you are travelling a reasonable distance, do not forget to bring a repair kit with you, extra tube , pump etc as it can be rough out there.