Going the Extra Mile: Can Pedaling Charge Your Electric Bike’s Battery?

For all the benefits of electric bikes, the downside is that you need to plug them in to recharge. But is there another way to do it? While putting your bike on charge after a grueling day in the saddle, you might ask yourself, “do electric bikes charge while pedaling?”

Unfortunately, most electric bikes do not charge while pedaling. Although some models harness kinetic energy through braking to charge the battery, the amount of charge is often inefficient. The only way to adequately recharge an electric bike is to plug it in while stationary/not operating.

Electric bikes offer several benefits, but unfortunately, they do not effectively charge through pedaling. Below we’ll further investigate the intricacies surrounding why most electric bikes don’t charge while pedaling, which models recharge while in use, and the technology that recharges electric bikes.

Why Don’t Electric Bikes Charge While Pedaling?

If you have any knowledge of cars, you’ll know that a car’s alternator converts the turning motion of the wheels into electricity which charges the battery, a very effective system. However, electric cars and bicycles do not follow the same principle.

The reason is that the energy conversion rate is too low (roughly 10% of the energy generated through pedaling is converted into electricity, which charges the battery.). In other words, you would need to travel 10 miles to charge a battery enough to run for 1 mile.

Unfortunately, this technology is unavailable in most e-bikes, as the amount of watts produced through pedaling is insufficient to adequately charge a battery.

Depending on the model, e-bikes require between 400 and 800 watts to charge their batteries. The average cyclist pedaling produces around 100 watts per hour (on a regular bicycle at a consistent pace).

With such a low economy, it’s not worth the effort, and the traditional method of recharging an e-bike battery through a charger is superior (taking roughly three to four hours to charge).

Why Do Electric Bikes Have Poor Energy Conversion Rates?

Electric bikes (e-bikes) do not effectively convert pedaling into electricity because they are not designed to do so.

Pedaling is the primary source of movement for a bicycle (regular and electric), which means the energy created by the pedals needs to move to the wheel (through a chain or drive shaft) to push the e-bike along. The priority for forward motion leaves little energy to charge a battery.

If you had to effectively harness the energy created through pedaling to charge a battery, you would severely stifle the e-bike’s movement. I.e., you would pedal to power a piece of hardware instead of moving forwards, drastically reducing your speed and increasing the effort needed to pedal.

An e-bike’s motor kicks in when you pedal (or use the throttle) to help you go faster or to maintain a constant speed.

If your pedaling were disconnected from forward movement and only powered by a battery, your riding experience would be completely altered (i.e., no matter how hard you pedal, you won’t go faster).

While e-bikes don’t charge the battery during use, most modern e-bikes have a built-in “cut-off” function that allows the battery to conserve energy while pedaling or braking.

While these technologies don’t directly put electricity into the battery, their incorporation into an e-bike means that the battery discharges at a slower rate (than if in constant use), which results in a better economy (how far you can travel before recharging the battery).

But What About Using Downhills?

While pedaling uphill or along a flat road is too inefficient to convert the power into electricity for battery charging, pedaling. At the same time, “freefalling” downhill is an opportune time to convert “excess” energy into electricity.

However, the lack of practicality of charging while freewheeling downhill is why manufacturers don’t offer this function, as they would need to include a device that switches between “charging” and “discharging” modes when the e-bike was in freewheel or regular use (peddling).

For example, most e-bike motors are limited to a certain speed (depending on the country). When you hit said speed, the motor disengages, allowing momentum to carry you onward without speeding you up.

While manufacturing specialized clutches and driveshafts to harness the energy for battery charging is possible, the process is currently too expensive to incorporate into the system.

As technology improves, we may see more features and gadgets that allow this type of charging/cycling.

Lithium-Ion Batteries Charge Best When Not Under Load

Electric bikes run on lithium-ion batteries, which are superior at holding a charge (to lead batteries).

Although you can charge lithium-ion batteries while under load, lithium-ion batteries charge best when disconnected (if you charge a battery while under load, it can “confuse” the charger).

Aside from charging under load, lithium-ion batteries charge optimally between 50°F and 86°F. Higher temperatures may cause the cells to deteriorate quicker, shortening the battery’s lifespan. If you cycle in hot (or cold) areas, charging your battery during use may inadvertently reduce its lifespan.

Why Do Some Electric Bikes Charge While Pedaling?

Although most e-bikes do not charge on the go, several break free from the mold.

The majority of e-bikes that offer charging-while-in-use are those that capture energy through regenerative braking.

A Brief Look At Regenerative Braking

Although this technological advancement is relatively new (in e-bikes), regenerative braking is one of the methods that manufacturers try to “recapture” energy to charge the e-bike’s battery.

Regenerative braking converts the e-bike’s kinetic energy into electricity which charges the battery by turning your motor into a generator.

Electric motors turn in a specific direction to turn your wheel while you use the throttle/pedal assist function. However, when you press the brakes, the motor switches directions, and the current is redirected to the battery.

This type of braking is more effectively employed in cars and other larger/heavier vehicles. An electric bike and rider do not weigh much, so their inertia (the ability to move in a particular direction) is not very high.

This “lightweight-ness” means that e-bikes stop quickly, reducing the time available to charge the battery. E-bikes using regenerative braking only charge roughly 5 to 10% of a battery’s capacity.

This braking is only available for e-bikes with a direct drive/gearless hub motor (motors found in the hub of the rear tire).

Prominent e-bikes which use a regenerative braking system include:

  • RAD Power Bikes (including RadCity 4, RadCity Step-Thru 3, and RadWagon 3)
  • Cooper Bikes (four electric bike models)
  • Opium (the 6.0 and the 4.0)
While some e-bikes charge while pedaling, others can be charged with solar panels.

Are There Electric Bikes That Recharge While Pedaling?

Although pedal-charging e-bikes are still a long way off from being the norm, the good news is that developers have already begun the process.

The ByAr Volta, a Dutch-produced e-bike, is growing in popularity for its sleek design and because the e-bike charges the battery when you pedal backward.

Most shaft-driven (no chain) bicycles have a rear hub allowing the motor to turn the other way and charge the battery.

However, they have a limited speed and are restricted to cruising around a city. Unfortunately, they cost a pretty penny, starting at around $4000.

While slightly different, this backpedaling is akin to regenerative braking.

As you move the pedals backward, the bike begins to slow. To use the charging function effectively, you’d need to reach an appropriate speed, coast, and backpedal, slowing the bike down and turning the motor into a generator.

The longer you backpedal, the more you’ll charge the battery. While this method works well on hills, it might not be so effective on straights (you lose speed as you put pedal power into the battery).

Although limited to a few models, backpedaling and other regenerative braking methods should continue increasing in popularity as time progresses. It is not unfeasible to think that, shortly, electric bikes will be more self-sufficient in their ability to charge.

Conclusion

Unfortunately, the technology to efficiently charge electric bikes while pedaling does not exist. While several models that use regenerative braking or backpedaling are available, their energy economy is not particularly great. Given sufficient time, these bikes will be “charged on the go,” but for the time being, the most effective way to recharge e-bikes is to plug into a charger while stationary.

Author

  • Miles Baxter

    Miles Baxter is an engineer with a longstanding love for bicycles, sparked by winning a mountain bike in a childhood lottery. Balancing a keen interest in mechanics with the thrill of biking, his career is a testament to the art of turning wheels and gears into adventures.

    Baxter Miles