If you are shopping for your first ebike or electric scooter, you might be confused by the numbers on the spec sheet. What is a watt-hour, and how is it different from an Amp-hour? Does it matter? How big of a battery do I need?
We're here to help you understand the numbers with the help of basic physics and math.
Chances are you will see a variety of numbers related to the battery on the electric bike or escooter. The most common ones are watt-hours, watt-hours, and watt-hours.
When it comes to energy capacity, watt-hours are the most useful unit. If you want to compare the battery sizes for two rides, you should look for the watt-hour rating on the spec sheet.
The bigger the watt-hour rating, the bigger the battery.
Many electric scooter companies still stick to the old formula of showing battery ratings in watt-hours, despite the fact that most ebike companies now show battery ratings in watt-hours. My friend, don't worry. The easiest way to find a watt-hour rating is to look at the volts and hours. The formula for you is here.
Ah * V.
That is it. By the same token, you can find a battery's Amp-hour rating by dividing its watt-hour rating by its voltage. The watt-hours can be divided by Amp-hours to find the voltage.
The above formula is an approximation, as the battery's voltage will vary during use. It is the easiest way to compare battery capacity among various escooters.
The motor's wattage doesn't tell you anything about the range. Although they are related, watt-hours and watt-hours are different.
The latter is a unit of power. The amount of power the ebike is able to draw from its battery over an extended period of time is what that means.
A motor with a higher wattage can theoretically go faster. It will drain your battery faster if you push the motor hard, but the motor's wattage isn't a fixed value, it depends on how hard you push the motor. The figures are averages.
The watt-hour is a unit of energy. It tells you how much power is needed to drain the battery in an hour.
It would take about one hour to drain a 250Wh battery, two hours to drain a 500Wh battery, and so on.
You shouldn't rely on watt to estimate range because the motor's wattage is not always constant. They usually can ramp up to wattages beyond their official rating.
There are some general guidelines you can keep in mind when it comes to the amount of energy used by a motor.
The batteries for ebike and scooter are usually between 400 and 600Wh. Lighter scooters and e bikes tend to be closer to the 300Wh mark, while heavier, powerful models tend to be closer to 1000Wh.
How far those batteries will go depends on how you use your bike or scooter. Higher assist or speed settings will use more energy, but things like the type of motor, wheels, or sensors can affect range as well.
For most people, knowing the watt-hour rating is the most important thing to know about an electric vehicle. You might be interested in how volts and Amp-hours come into play. The following is a simplification and can be a little confusing.
The most common voltages on the market are 36V, 48V, and 52V, although you will occasionally see lower or higher ratings too. A higher voltage battery will usually be able to output higher power and maintain high performance at low battery levels.
It is thought that higher voltage batteries will use less current at a fixed power rating, which will translate to less heat and damage to the motor for a given performance level. The risk of electrocution can be increased by higher voltages. Commercial ebikes rarely go beyond 52V.
The implementation of technology is more important than the actual specifications. Some of the best hill-climbing e bikes I've tested have used 36V motors, while I've had weaker pedaling experiences out of some 48V e bikes. I have experience with higher voltage batteries being better than lower ones.
Amp-hours is a useless metric for most ebike and scooter riders.
It should only be used for comparison on e bikes with the same voltages. A 24V 20Ah battery has less range than a 52V 15Ah one.
If you want to know the range of an electric bike or scooter, look at the watt-hours.
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