One of the most common questions people ask about electric bikes is, do ebikes charge themselves? After all, when you are pedaling or the bike is moving, you are creating energy that could be transferred back to the battery, right? Well, kinda…
Do ebikes charge themselves? Electric bikes equipped with regenerative braking can charge themselves. One can expect 5-10% return on their charge. Charging an electric bike by pedaling is not practical or recommended. It would take 11 hours to charge a 672 Wh battery by pedaling.
Can You Charge an eBike by Pedaling?
Charing an electric bike by pedaling sounds pretty awesome right? And while it sounds great, the reality is a little different.
Technically, yes, you can recharge a bike by pedaling. But is it worth it? Well, there are two scenarios we will look at. Charging while pedaling and charging when stationary.
If you are trying to get from point A to point B, then charging the bike at the same time will be self-defeating. In order to charge the bike battery, some of the energy need to move the bike forward would be diverted back into the battery. Not only will you go slower, but during this process, energy will be lost, which means you’ll be exerting more energy.
But what if you wanted to charge your battery like a stationary bike, could that work? Well, you could, but it would take a lot of work. Let’s look at the numbers…
First, we’ll need to find out how much energy is required to charge an electric bike battery. A Rad Power Bike battery is 672 Wh. Next, we need to find out how much energy a person could produce.
A normal person, cycling 8 hours a day, can produce 1 kWh per day. But, there is energy lost converting the mechanical energy to electric energy to chemical energy, where the power is stored in the battery. This means, instead of a person producing 1 kWh per 8 hours, they are producing half that, or 0.5kWh.
At 0.5kWh being produced every 8 hours, you’ll need almost 11 hours to fully charge an electric bike battery. That is 11 hours without breaks at a constant speed. That’s quite the workout!
But will I save money? Because you aren’t using electricity to charge your ebike, you might think you’re saving money, right?
Actually, quite the opposite! After all, humans are fueled by calories, and calories cost money. It would take about 578 calories to fully charge a 672 Wh battery. But, it’s not that straight forward. Only about 1/4 of the energy from calories is converted into mechanical energy (ie pedaling). The rest of the calories are spent keeping you alive, like your lungs breathing and heart pumping. There are also things like heat loss as well. So, overall, it would require 2312 calories to fully charge an electric bike.
If we take one of the cheapest foods, white rice, and calculate cost per calorie, we get about $0.41 per 2,000 calories. That’s 47 cents to charge your bike. Considering it only takes 4-11 cents to charge an electric bike using electricity, you would be spending 10x more money to charge your battery.
What about Regenerative Braking?
There is one case where charging your electric bike battery while moving is both possible and practical. This is in the case of regenerative braking.
Regenerative braking is feature on some ebikes equipped with a direct drive motor that charges the battery when braking. This essentially works by turning the motor into a brake, where forward energy is diverted back into the motor to charge the battery.
On the Rad Power Bike Radwagon, regenerative braking is applied whenever the front or rear brakes are activated
Regenerative braking is active on the RadWagon whenever the front and/or rear brake lever is applied, which flips and electronic switch, turning the motor into a brake. This feature recharges the battery pack when the brakes are applied while coming to a stop and traveling downhill.
How much energy can you get back? Some people who “hypermile” can get back as much as 10-12%. If you apply your brake longer instead of stopping suddenly, you’ll get more power back. You can also apply the brakes on downhills to get even more charge.
Self Charging Electric Bike – Is It Possible?
As we’ve explored, there’s no such thing as a self charging electric bike. Some bike manufacturers may make that claim, but their bikes simply make it harder to pedal on flat ground. And making it harder to pedal defeats the whole purpose of owning an ebike in the first place.