Here at Electrek we love DIY projects. And solar power. And electric bikes. So when those three can be combined, that’s pretty much a trifecta in our books.

In this case, we got the chance to chat with the builder of an awesome solar charging utility trailer that the industrious e-bike owner built to upgrade his ride.

DIY solar charging e-bike trailer

The creator of the awesome little trailer is a redditor who preferred to remain anonymous (wisely forgoing the heaping serving of internet fame that Electrek would surely bestow upon him), so we’re going to call him Bob.

Bob built the base of his utility trailer using a Wike DIY kit.

The kit includes the basic hardware such as the corner pieces, wheels, and other small parts required for the trailer, but lets you add the structural components to customize the size and construction to your own needs.

The frame was built using 1/16″ aluminum square tubing and the walls of the trailer were made from galvanized sheet metal meant for roofing, which Bob then caulked together to dampen out the rattling sound.

For the roof of the trailer, Bob used a rigid solar panel that he mounted on gas pistons that allow it to open easily and hold its position. A bungee cord is used to adjust the angle for optimum sun, but he keeps it closed while riding so it doesn’t turn into a wind sail at the wrong moment.

The flat panel is still fairly efficient for solar electricity generation, but angling it towards the sun when the bike isn’t moving helps boost the efficiency even more.

Speaking of boosting, to get the 12V panel’s DC voltage up to the 54.6V required by the battery, a simple boost converter was used that employs MPPT charging to get the maximum possible efficiency.

As is usually the case with these types of DIY electrical projects, Bob had to do a bit of an electrical connector square dance to make everything play nicely. A mixture of XT60 connectors, MC-4s and 5.5×2.1 barrel connectors were used to match the solar panel, charge controller and charge port on the e-bike’s battery.

Bob’s setup is designed to charge his Rad Power Bikes RadRunner Plus electric bike, whether the bike is operating or turned off. He measured the output of the panel at around 100W in direct sunlight, which isn’t enough to provide infinite range when the sun is out (that’d probably take 300-400W of power or around 3-4x the size of the current trailer’s roof).

However, the 100W from the panel is likely enough to help offset the extra power required to pull the trailer. If so, that basically gives Bob back the energy he would have spent on lugging around a less-than-aerodynamic box behind his bike.

The goal of course wasn’t to offer endless range, but rather to provide an easy way to slowly recharge the bike when in use for several days. Camping trips were one example Bob gave, where he could spend a couple days out in nature and get a full charge each day directly from the sun.

We’ve seen other interesting DIY solar charging projects for e-bikes before, and I’ve done my own experiments with simple portable power stations and their matching solar panels, but Bob’s project is one of the nicest and cleanest mobile solar charging solutions we’ve seen. Plus the fact that it’s part of a sturdy trailer that is rugged enough to carry a few hundred pounds of concrete sacks sure makes it even more impressive!