Exert from “The Power of Electric Bikes” by Jim Turner
The Battery is The Gas Tank
The key to any electric vehicle is the battery and how much energy it can hold. The battery is the gas tank. The battery holds energy. Power accelerates the car, but the size of the gas tank (energy capacity) determines the distance. For a gas car, you buy energy in the form of gasoline. In an electric vehicle, you buy energy in the form of Kilowatt –hrs. This is the way you buy electricity in your house. Your house electricity bill charges you for the amount of kilowatt-hrs of energy you use in the month.
High Power With a Small Gas Tank Doesn’t’ Get you Far
If a high horsepower Corvette has a small gas tank, the car doesn’t go very far. An electric vehicle needs a battery with a high energy capacity to go far. The amount of energy is measured in kilowatt-hrs. An electric vehicle’s range is constrained by batteries. Batteries don’t have the energy density of gasoline, meaning they provide less energy in terms of size and weight compared to gasoline.
Electric Vehicles Need High Energy Batteries, Not High Power
Energy is the amount of power used over time. An electric vehicle must be more efficient with the use of energy than a gas car. With an electric vehicle, a battery with high energy, not high power is preferred. This gives the vehicle the ability to travel long distances. Some batteries put out a large amount of power, but they don’t have very much energy. That means the vehicle will accelerate very quickly, like a high horsepower Corvette, but will not go very far, because the size of the gas tank is small..
Humans Have Energy and Power Differences Too
In the Olympics, there are sprinters and marathoners. The sprinters who run the 100 meter dash have very large muscles. They can go really fast and have huge amounts of power, but they don’t have much energy left because they use it all up in 100 yards. The sprinter isn’t interested in energy density, he wants all-out horsepower. In contrast, the marathon runner can run a marathon averaging 5-minute miles because he uses his energy so efficiently. The marathon runner wants a balance between power and energy. He needs power to have the speed and energy to go the distance. This is the same with an electric vehicle. Electric vehicles need high energy density in their batteries to go the distance.