What Are Electric Bike Batteries?

The battery is one of the most important components of an electric bike. Designed to supply power to the electric motor, the battery enables the electrical assist features to propel the e-bike forward.

E-bike batteries come in various types and charging capacities. These characteristics influence which electric bikes they are compatible with and how far they can take you on a single charge. Thus, it’s worth understanding how they work so you can choose one that best fits your needs.

In this article, you’ll find out what batteries are used in electric bikes, their key metrics, and what sized batteries are best for certain e-bikes.

What Type of Battery is Used in an Electric Bike?

As battery technology has advanced, so has the power and travel range of electric bikes. Early electric bike models ran on lead-acid batteries. These batteries were great for their time but have been replaced by better alternatives

Lithium-ion Batteries

Lithium-ion batteries power the vast majority of electric bikes, with the estimated size of the global lithium-ion battery market being 54.6bn USD.

The widespread adoption of lithium-ion is due to the various improvements made over older lead-acid batteries. Not only are lithium-ion batteries smaller and lighter, but they also hold their charge for longer when idle and in use.

Lead Acid Batteries

The first electric bikes ran on lead-acid batteries, which were popular due to being inexpensive to produce and easy to recycle.

Lead-acid batteries have fallen out of favor due to their bulky size, heavy weight, and low travel range. In fact, they last only half as long as lithium-ion batteries and weigh nearly three times as much.

Nickel-Metal Hydride (NiMH) Batteries

NiMH batteries are a better alternative to lead-acid batteries. They are more eco-friendly and more resilient in cold weather, which is why they are commonly found in portable electrics.

NiMH batteries have a lower charging capacity than lithium-ion batteries, so they don’t travel as far on a single charge. They also have a higher self-recharge rate, so they lose their charge faster when idle.

FURTHER READING: What is an Electric Bike and How Does It Work ?

Key Metrics of E-Bike Batteries

When shopping for a new electric bike, you’re going to encounter technical terms like voltage, amp hours, and watt hours. Unless you know these terms, you risk choosing an electric bike that does not meet your needs.

To help brush up on your knowledge of e-bike batteries, here is a breakdown of their key metrics.

Watts (W)

Short for wattage, watts describe the amount of power it takes for an electrical device to perform a task.

Electric bike manufacturers use two watts ratings to promote their electric motors. Continuous (nominal) power is the maximum power output over a given period. Peak power is the maximum power output of a short burst.

The average wattage rating for electric bikes is between 250 and 1000w. The higher the wattage rating, the more power the engine consumes. Thus, the faster the e-bike goes.

Watt Per Hour (Wh)

Wh is a unit of measurement. It describes the amount of work that an electrical device does when using one watt of power per hour.

To calculate the Wh on an electric bike, multiply voltage and Amp-hours. Let’s apply this calculation to an electric bike with a motor that has a 36-voltage rating and a 7 Amp-hour rating. Here is what this calculation would look like:

36V x 7Ah = 252 Wh

Voltage (V)

Voltage, or volts, determines the force of flow from the battery to the electric motor. The average voltage rating on an electric bike is from 36 to 52V. The higher the voltage rating on an e-bike battery, the more power it provides to the electric motor.

In the UK, the legal max power output for an electric bike is 250w, which is typically paired with a 36V battery.

Amperes (Amps)

An amp is a unit of measurement that describes the amount of power being drawn from a battery at any given time. Like voltage, the higher the amps rating, the more power the engine can produce.

Most electric bike manufacturers advertise amp-hours (Ah) over an amp rating. Ah is a more accurate representation of a battery’s travel range.

Ampere Per Hour (Ah)

The Ah rating describes how many amps a battery can deliver over a set amount of time. For example, a 25Ah battery can provide up to 25 Amps per hour, or up to 50 Amps for two hours.

The Ah rating is used with the voltage rating to calculate an electric bike’s Wh rating.

Battery Management System (BMS)

Despite being an often-overlooked component, the importance of a BMS on an electric bike cannot be understated. Connected directly to the e-bike battery, the BMS is responsible for monitoring the battery and the charging process.

The BMS ensures that the battery supplies the right amount of power to the motor. This helps prevents over-charging and under-charging. It also evenly distributes voltage to all battery cells.

What Size Battery is Best for an Electric Bike?

The best battery size depends on your needs and physical capabilities. Consider the average travel range of each trip you take.

Will you do short trips around town, or long-distance outback riding? A battery capacity of 5 to 10Ah will suffice for shorter commutes but choose 10 to 20Ah for longer commutes.

Another deciding factor is your physical capabilities. While more powerful batteries go further on a single charge, they are also larger and heavier.

Decide if you can handle the additional weight, as the extra bulk will affect the ride feel. For example, you may need to anticipate corners and turn sooner than you would on a lighter e-bike.

Do Electric Bike Batteries Need to Be Replaced?

Like all e-bike components, batteries don’t last forever, and when they fail, you need to replace them. There’s no set lifespan for electric bike batteries, as most last for about two to five years (10,000 to 30,000 miles). Afterward, they start to lose their charging capacity.

What does this mean? The battery can no longer hold as much energy as it once could, resulting in a shorter battery life per charging cycle. Once your e-bike battery reaches its rated number of charging cycles, it should still be able to get 70% of its original capacity.

When replacing your e-bike battery, ensure the replacement battery is compatible.

Read the manufacturer’s guide for information on recommended voltage and ampere ratings. Choose a replacement battery with the same voltage and ampere ratings as your existing battery.

Wrapping Up

The battery is the lifeblood of any electric bike. Without one, you cannot use the electrical assist features. The result? A more traditional riding experience. With the right battery, though, you can use the pedal assist and throttle to ride for longer, sweat less, and climb steep hills easily.

Need a replacement battery or charger? Explore the full range of replacement parts on our online store.