Brompton C-Line Ebike Conversion with a Grin Kit

I’ve always admired the Brompton for its clever engineering, especially its folding mechanism—which, in my opinion, is one of the best in the world. Recently, I had the opportunity install a conversion kit on a Brompton C-Line and I was genuinely impressed by how well the conversion turned out.

Although Brompton offers factory-made electric versions, they come with a steep price tag. By opting for a conversion, you not only save money, but you also get a higher-quality kit with more customization options and features like regenerative braking (which recaptures energy during braking to recharge the battery). For this build, I used a Grin Technologies Brompton Kit, featuring their Crystalyte SAW20 direct drive front hub motor. This kit is designed specifically for the Brompton, and Grin’s attention to detail really shows.

Here is a video showing all the components included in the kit:

Components Used

• Motor: Crystalyte SAW20 (direct drive)
• Battery: 36V 10Ah, mounted in a front bag for easy removal
• Display: 600c display
• Custom Parts: Torque arms and motor controller bracket from Grin Technologies

Grin provides custom torque arms to reinforce the fork and a motor controller bracket that sits neatly above the front fender.

Installation Highlights

The conversion was relatively straightforward thanks to Grin’s well-thought-out kit. The biggest challenge was cable management: ensuring that everything stayed tidy without affecting the bike’s folding mechanism. Some small adjustments were needed to the handlebar angle to accommodate the new display and throttle, but once that was dialed in, the bike folded just like before.

One small hiccup was the motor spinning in the opposite direction from what was labeled on the motor casing. But since this is a direct drive motor, direction can easily be reversed in the setup, so it wasn’t an issue.

Performance

• Top Speed: 30 km/h
• Range: 30–40 km, depending on assist level
• Folding: Still folds fully—only the battery needs to be removed
• Regenerative Braking: Not enabled in this build, but possible with the Crystalyte motor

Electrifying the Brompton opens up an entirely new way to use the bike. With the added pedal assist, hills become manageable, and the small form factor still makes it perfect for multimodal commuting. Whether you're hopping on the SkyTrain in Vancouver or zipping through downtown traffic, this electric Brompton is a joy to ride.