Let’s dive in.

When it comes to using traditional bicycle frames for long-range e-bikes and high-speed models, the challenge is quite significant. It's similar to trying to fit a gasoline engine into a horse-drawn cart. While Carl Benz managed to do it successfully, the design wasn’t very reliable — as demonstrated by his wife Bertha, who took the first ever car on a long journey with her children. In the photo, you can see what that original model looked like.

Courtesy of Mercedes Benz

It doesn’t look much like a modern car, does it? That’s because early inventors used what they had available. Carl Benz used a cart, and today’s engineers often use standard bicycles. However, this approach has proven problematic — trying to adapt regular bike frames for electric bikes often leads to structural failure, just like how old horse-drawn carriages couldn’t handle the weight of a gas engine.

The reason behind this is the different distribution of mechanical stress. Electric bikes require large batteries and powerful motors, which add significant weight and torque. Unlike traditional bikes, which are powered solely by human effort, e-bikes rely on strong motor torque that puts more pressure on wheels, rims, and spokes. Aluminum frames, especially those with forks, are particularly vulnerable to twisting forces from high-torque motors. Despite many attempts to modify these frames, failures still occur — whether in bolts, welds, or other joints.

This is why specialized e-bike frames are now being developed. After exploring various options, Delfast came up with our own unique frame design. But let’s take a closer look at the battery — one of the most critical components of any e-bike.

A high-capacity battery pack is essentially a collection of individual cells connected together. This makes it bulky and heavy, as shown in the image below:

The size of the battery directly affects its capacity and, therefore, the range of the e-bike. The larger the battery, the longer the ride — which is crucial for an e-bike. A 20 km range isn’t practical for most users. So, the battery we use in our e-bikes is designed to be both powerful and safe.

But here’s the catch: lithium-ion batteries are highly flammable and need proper protection. With traditional bike frames, it’s almost impossible to safely house a large battery. First, there’s not enough space, and second, small batteries don’t provide enough range. For city riders, this might be acceptable, but for long-distance travel, it’s not enough.

That’s why many e-bikes today have small batteries tucked away where a water bottle would go, along with a motor controller in a black plastic box. It looks a bit like the first cars — not very advanced, but functional for short trips.

However, for a large, high-capacity battery, such a design is impractical. Not only is the space limited, but the battery also needs protection from impacts and temperature fluctuations. Lithium-ion batteries can get very hot, even reaching melting points if not properly cooled. We’ve made sure to avoid that risk by designing a protective frame that acts as a housing for the battery and control systems — much like a PC case.

Here’s what it looks like:

This frame is not just a structure; it’s a protective casing that keeps the battery safe while keeping the center of gravity low. A lower center of mass improves stability and handling, making the e-bike more agile and easier to control. The frame is designed around the battery and electronics, similar to motorcycle construction rather than traditional bike design.

So, how do you choose the right frame size? It’s actually quite simple. By adjusting wheel size or saddle height, the frame can be adapted to cyclists of all heights — from 166 cm to 180 cm and above. Just talk to your sales manager when purchasing your e-bike, and they’ll help you find the perfect fit.