Important technical parameters of electric bicycles

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The "range" claim
The electric bicycle range is defined as follows: when the new battery is fully charged, the rider's weight is configured to 75 kg on a flat secondary road (without strong wind conditions), and the battery voltage is less than 10.5V/section to be disconnected, under the above conditions, the range is called the electric bicycle range.

The range of electric bicycles with 36 volts 12 amps high quality battery is about 45~60 km, while some individual manufacturers' claims will rise to 70~80 km, which is suspected of false propaganda. This is because this nominal value means that the efficiency of the motor is nearly 40% higher than the efficiency of the motor used by the brand-name factory. If a brand-name factory produces the motor in the above described working condition when the efficiency of 75%, the motor efficiency of the manufacturer of the nominal 70 ~ 80 km has reached more than 100%, which is obviously impossible, which is particularly worthy of the attention of consumers.
In the actual use process, how many kilometers can be driven with sufficient power in the end? This is related to many factors, including those related to the manufacturer, mainly the efficiency characteristics of the motor, the capacity and life characteristics of the battery; factors related to other objective circumstances: the weight of the rider, the frequent riding road conditions, whether the need to use the brake often, how the cyclist's cycling habits, etc. Another issue that needs frequent attention is that the battery capacity will gradually become smaller with the growth of use time, and the distance that can be driven with sufficient power will also decrease. When the maximum driving distance of the old battery cannot meet the traffic needs of a day, you can consider sending the battery for repair or replacing it with a new one.
Motor maximum output power and maximum output torque
The maximum output power of the motor is the key indicator to measure the torque capacity of the electric car wheel. Generally, each electric car factory will set a maximum working current according to its own technical level, and when the external load is large, the working current of the electric car reaches the maximum, and the output power also reaches the maximum. For example, if the maximum working current of an electric car is set to 12A and the working voltage is 36V, the maximum input power reaches 432W. Then, for example, if the maximum current of an electric car is limited to 15A and the voltage is also 36V, the maximum input power reaches 540W. Obviously, some motors keep high efficiency in high current state, while some motors have serious decrease in efficiency in high current state. Most electric car motor in 430W input efficiency has been reduced to about 55%, the maximum output power of 430 × 0.55 = 236W, the maximum output torque is only 14N.m, it is obvious that a maximum torque of 25N.m electric car and a maximum torque of 14N.m electric car in the climbing ability, allow the load capacity and the ability to resist wind resistance and many other aspects will have The feeling of riding is completely different. The easiest way to test the maximum output torque of a vehicle is to "climb with weight".
Motor rated output and output power range
Motor power rating is an important parameter when a motor is tested for driving, it means that when the motor works at this power point, the motor can run continuously and reliably, characterizing the thermal balance point of the motor design. Generally the rated power point of electric vehicle motor can be 150W, 180W or 200W or more, the higher the rated point means the better the thermal performance of the motor and the higher the cost. Since it is impossible to work in an unloaded state, the weight of a normal cyclist will generally reach more than 30kg, and considering the normal wind resistance and other factors, the minimum working point (output power) of an electric car is about 80W, and the maximum output power depends on the design scheme of the motor. The output power of the better electric bikes available in the market can generally reach 200W or more, while the individual poor motors are less than 200W. The larger the output power range, the better the riding performance.
Electric vehicle efficiency and efficiency interval
Electric vehicle efficiency is a comprehensive reflection of electric hub efficiency, control system efficiency and mechanical rotation loss, but mainly depends on the efficiency of the electric hub (motor), which can reflect the same battery, the same riding load conditions of the length of riding mileage, high efficiency is long riding mileage, low efficiency is vice versa, for users, the purchase of higher efficiency to reach the electric vehicle is undoubtedly the right.
However, the efficiency of the electric car also needs to have a range, because the motor efficiency is different under different torque, expressed as a saddle-shaped curve form, some electric car motor in a small power when the efficiency is high, once the output torque increases, the efficiency value drops sharply, this kind of car is often shown as a flat road speed is very fast, once the uphill speed drops sharply, the power consumption level will also increase significantly.

The concept of efficiency interval to replace the concept of pure rated efficiency is an important feature of electric bicycle, because the vehicle load is a very variable load, its working point will be with the vehicle load state, road slope, driving wind resistance of different and great changes, the pursuit of a high efficiency of a working point and ignore the efficiency characteristics of the whole working area is meaningless.

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