Whoever thought to add an electric motor to a bicycle deserves a prize for such an innovation. Electric bikes are a popular commuter tool and way for anyone to get outside into fresh air. While these bikes overcome many of the problems inherent with standard bikes, especially people tiring too soon, they do come with the problem of having to navigate the terms used for their electric components to make the best selection.
If you want to purchase an electric bike of your own, you need to understand wattage, voltage and amp-hours and what they mean for your ride to make the best decision for your lifestyle. Here, you will find the definitions and more about the operation of e-bikes.
How Does an Electric Bike Work?
Electric bikes use a motor to assist the movement of the pedals, making riding the bicycle less taxing. Some designs allow the bike to move forward under its own power from the motor while others require your assistance to pedal.
Don't confuse electric bicycles with motorcycles. The electric motor and battery don't last as long as a gasoline-powered engine. However, e-bikes are better for the planet because they do not generate polluting exhaust when you ride them. They also are a healthier option for you because you will have to use your power to move the bike, which will improve your cardiovascular fitness.
While you might think electric bikes don't have an upper limit for their speed, thanks to the addition of a motor, they do. Because federal regulations under the 2002 Consumer Product Safety Act regulate the definition of low-speed electric bikes, you will have a speed limit for how fast you can go with motor assistance. Depending on the bike you have, you may have a speed limit of 20 to 28 miles per hour (mph).
E-bikes have three classes in states that define what an electric bicycle is. Check with your state laws because some places regulate the operation of certain e-bike classes to specific age groups.
- Class 1: These bikes assist the rider while they pedal at speeds up to 20 mph.
- Class 2: These bicycles may use a motor only to propel the bike up to speeds of 20 mph.
- Class 3: The fastest bikes only provide motorized assistance when the rider pedals, up to 28 mph.
Electric bikes have three main components that set them apart from standard bicycles — the battery, the motor with its controller and the sensor.
1. The Battery
The battery powers the motor. This device's capability for generating power and how long it lasts are where the numbers for wattage, voltage and amp-hours come into play. To keep these weighty parts of the bike from upsetting your balance, they have a position low and centered on the bicycle.
While bike batteries have shrunk in size and increased in power since converting from lead-acid to lithium cores, they still contribute a significant amount of weight to your bike.
2. The Sensor
To prevent electric bikes from going too fast, they have sensors that monitor your speed to determine when to instruct the motor to turn the throttle or pedal assist on or off. The sensors may measure speed or torque. Both act in similar ways, though. The speed sensor watches how fast you travel. A torque sensor, however, monitors how hard you pedal, as harder pedaling correlates to faster speeds.
3. The Motor
Electric bikes use a motor to boost your ability to ride. If you tire out while riding an e-bike, you can use the throttle to help you move. Pedal-assist also kick in while you pedal the bike, allowing you to use less effort. As soon as you stop pedaling or go over the preset speed limit of the bike, though, the pedal-assist stops.
The motor changes electric power into mechanical work that it uses to help turn the bicycle's wheels. Manufacturers have three positions for placing the motor — the front hub, rear hub and in the center of the bike. Motors placed on the front hub have become less popular today than those installed in other locations on the bike. You will typically find these front-installed motors on low-end e-bikes.
Rear-hub motors drive the bike from the rear wheel and integrate with the bicycle gears. The motor in this position improves traction and handling thanks to its connection to the gearing. With better control, rear hub motors often appear on mid-class e-bikes.
Premium, and very expensive, electric bikes have their motors near the center of gravity and attached to the frame. This motor position does not prevent you from quickly changing tires on your bike while making the bike stable.
E-bikes are typically made with electronic components that have secure coverings with tight seals to prevent damage from light rain. They can withstand a variety of climates, but it's important to use common sense and avoid overexposing an e-bike to significant water and/or rain.
Now that you know about the parts that set an e-bike apart from a regular bicycle, learn more about the power options and what they mean.
Electric Bike Wattage Explained
The wattage is one aspect of your bike's battery power. Along with voltage and amp-hours, the wattage informs you about the potential speed and performance of your bike. Understanding the differences between wattage and watt-hours will also help you to see how long you can ride your bike before you need to recharge it.
1. What Is Wattage?
Wattage refers to the power output of a motor. You will see wattage listed with the motor power as both peak and nominal power. These ratings measure the ideal calculated value and typical operating capability of the motor, respectively.
Peak power indicates ideal power from the motor under full throttle and ideal operating conditions. Your motor will likely never reach this value because some power gets lost through friction and other means.
To give you an idea of the realistic amount of power you will get from the motor, manufacturers list the nominal wattage. At the highest power levels, the nominal wattage will typically be 75% of the peak operating power. This value is the second number you see listed with motor power and reflects actual usage. Use this number when calculating watt-hours.
Watt-hours tell you how long your bike can last with its specific motor before you need a recharge and will also dictate the top speeds your e-bike is capable of going.
2. Why Does Wattage Matter for an E-Bike?
The motor power wattage helps you to calculate the watt-hours for your bike. Motors with higher watts will require a longer-lasting battery to support the extra power.
Watts come from the product of the battery's voltage and the motor controller's amps. For example, a bike with a 52-volt battery and 20-amp controller will produce an ideal wattage of 1,040 watts.
52 volts x 20 amps = 1,040 watts calculated power
Find the nominal motor wattage by multiplying this value by 0.75 or 75%.
1,040 x 0.75 = 780 watts nominal power
You calculate watt-hours by multiplying the battery's voltage by its amp-hours. For instance, a 52-volt battery with 13 amp-hours will produce 676 watt-hours of power.
52 volts x 13 amp-hours = 676 watt-hours
To use this information to calculate how long your bike's battery can last at full throttle, divide the watt-hours by the nominal motor wattage. For the above example, divide 676 watt-hours by 780 nominal watts.
676 ÷ 780 = 0.867 hours
Multiply this value by 60 to find out how many minutes the battery will last.
0.867 hours x 60 minutes = 52 minutes
This value reflects running the bike at full throttle continuously. You can save battery life by pedaling more and using the motor less frequently. There are a lot of other factors that affect riding range and battery life, including total payload, average speed, tire pressure, and much more. Ideally, e-bikes supplement your biking skills rather than take them over.
Electric Bike Voltage Explained
The voltage for your electric bike will depend on the bike's battery. Lithium batteries offer much higher voltages compared to their older lead-acid counterparts.
1. What Is Voltage?
Voltage measures how much power the battery can send to your bike's motor. Higher voltage means more power can flow from the battery to the motor in less time, boosting performance. Combined with amp-hours, the voltage gives you an idea of the battery's watt potential.
You will see the voltage listed with the battery. Batteries for premium bikes might be 48 or 52 volts. Even if you have a lower voltage required for your bike, you can still use a higher voltage battery to boost the performance. Most bike motors will allow for a specific amount of voltage overage before they break down.
For some bikes, such as those from us at Juiced Bikes, the motors are backward compatible with some lower voltage batteries. For instance, you can use either a 48-volt battery or a 52-volt model on the RipCurrent S bike. Other bike brands do not offer this capability to use lower voltage batteries with higher voltage bikes.
Currently, 52 volts is the highest amount for electric bike batteries. Higher voltages likely won't appear on existing electric bike models as it would tip the voltage into the high-voltage range, which would require much stricter regulations.
Every bike in the Juiced portfolio includes the industry leading 52 volt battery.
2. How Does Voltage Impact an Electric Bike's Operation?
E-bikes will have a voltage range you must stay within when selecting your battery. Choosing a higher battery voltage can improve the performance of your bike.
Higher voltage batteries operate more efficiently, which explains why they can boost your bike's performance. These higher voltage batteries need less current while supplying the same amount of power as lower-voltage batteries. Since they need to work less, they have greater efficiency and a much longer battery range.
Higher voltage batteries will help your bike get the extra push it needs to climb hills or move more massive people or cargo. It does this by getting the electricity from the battery to the motor faster compared to lower voltage batteries.
Electric Bike Amp-Hours Explained
If you need to know about your battery's capacity, look for its amp-hours. Related to the amps measurement, the amp-hours give you a clear idea of how long your battery will last.
Amps measure the output of your battery. Amp-hours indicate the capacity of your battery by noting how much electricity your battery can put out in an hour at top voltage. The higher the amp-hours, the longer your bike can run, generally.
1. What Are Amp-Hours on a Battery?
Amp-hours for your bike's battery give you an idea of how long the battery will run before it needs a charge. For example, if you have a 20 amp-hour battery, it will last for 20 hours providing one amp of power. Should your motor draw more energy, it will last less time. At two amps per hour, the battery will last for 10 hours.
Think of amp-hours as the gas tank with amps as gas. Higher amp-hours will last longer with similar bike use and energy draw.
2. Why Do Amp-Hours Matter for E-Bikes?
The amp-hours and battery voltage are both essential factors in finding out how long you can ride your electric bicycle on a single charge. As noted, the product of these gives you the watt-hours.
Because amp-hours act like a gas tank, amps as gas and volts as gas flow, these parameters help you to see how long a charge will last at maximum capacity, which gives you watt-hours. Without knowing amps or amp-hours for your bicycle's battery, you would find comparing models complicated. Amps also help you to find the best charger for your ride.
You will see amps listed with the battery and the charger. Higher amps on the charger will recharge your bike much faster. The amps listed for the charger indicate how many amps the charger will move per hour into the battery.
For example, a standard two-amp charger adds two amps of power back to the battery each hour. It would take 5.2 hours to recharge a 13 amp battery from 10% to 90%. If you replaced the standard charger for an ultra-fast model that moves seven amps per hour, the charging time drops to 1.5 hours.
Need a Bike?
Watts, volts and amp-hours all play roles in the quality and longevity of your e-bike. However, you also have to know the construction of your bike will live up to high values for these statistics. Look for trusted names in electric bikes, like Juiced Bikes. We build high-quality, high-performance rides for the daily commuter, fitness enthusiast, casual rider and weekend off-road warrior.
Have you decided you need an e-bike to ease your commute or make riding more fun? Explore our high-performance electric bicycle options at Juiced Bikes. We specialize in giving you the ultimate thrill when riding, which is why we don't hold back when it comes to adding features. Our philosophy for bikes is "more features, more fun." We think you'll agree when you choose one of our ready-to-ride e-bikes. Biking will never be the same for you.