Brompton powers up its folder with new Brompton Electric

Nov 26, 2023

Hub-based motor and battery adds a little extra weight and a lot of extra cost

By Paul Douglas

Published: July 29, 2017 at 11:05 am

Brompton has entered the e-bike market with the announcement of its new Brompton Electric, a familiar-looking folder based on the brand's classic design, with an added 250W front hub motor and a battery bag which sits on the front of the bike.

The bike folds to the same size as a non-powered Brompton, with an additional 1.5L battery bag that can be carried as a shoulder bag when it's not on the bike. The battery also features a USB charging port for mobile devices A larger 20L bag is also available if you want to carry more stuff around.

The Brompton Electric has four modes, ranging from no assistance, through to a high level of assistance. With a claimed range of between 25-50 miles, the bike should have enough juice for even the lengthiest of urban commutes.

Despite the slightly unusual placement of the motor on the front wheel — unusual at least for a production e-bike, where the motor is usually based around the bottom bracket — this is not a throttle-controlled system. Like most others on the market, the bike includes a "smart, integrated torque and cadence sensor" to control the levels of assistance provided.

The battery also powers a set of Busch & Müller LYT lights for year round, hassle-free running.

BikeRadar has today been given a first look at the new Brompton Electric that the UK company hopes will transform city commuting and get more people onto two wheels.

Five years in development, the bike retains the looks and practicality of the original Brompton, adding a 250-watt front hub motor to the equation developed in conjunction with Williams Advanced Engineering. We went ‘under the hood’ with the company's chief design and engineering officer Will Carleysmith.

"The fold is the killer feature of the Brompton, it's what the business is built on," he explains, "and so very, very consciously we wanted to keep that and make the whole thing as seamless as possible."

The fold also helps to explain the decision to go with a front hub motor. "We looked at several options," confirms Carleysmith, "but the design of our bike means we couldn't fit a motor in the crank, and we wanted to keep the convenience of having gears so that ruled out the rear hub.

"We talked to some Asian companies about front hub solutions, but they couldn't deliver the standard we were looking for. Eventually we teamed up with Williams, and F1 is a very specialised world where they have an electrics person, a gears person, a motor person, all in one place. They were able to build something that we considered good enough for Brompton.

"We started out with a very good clutch, we killed that and went on to an even better clutch, so there is a very high quality of manufacture. Then we had to put our expertise into getting them made: F1 teams don't need to worry about mass manufacture.

"But if you want to know how is this different from a Chinese motor, then the really smooth super low friction front hub would be an excellent visible example of the knowledge and work that has gone into this."

The torque and cadence sensors, which are in the crank, measure your effort to kick in the motorised support, and on my test ride around St Paul's Cathedral in London that motor kicked in quickly and smoothly to put a smile on my face as I raced away from traffic lights and breezed up inclines at a very healthy pace. Like all UK e-bikes, the Brompton Electric has a 15mph speed limiter.

Another mark of the bike is its simplicity of use. The engineers at Brompton put in the hours of thought so the rider doesn't have to.

The decision to put the 300Wh battery – which allows for a range of 25-50 miles – in a separate bag rather than on the frame not only keeps the essential Brompton fold intact, it also allows the battery to be charged away from the bike and for it to be removed when the bike is being carried to help spread weight (the two-speed bike weighs 13.4kg, the battery 2.8kg).

The battery bag itself clips on and off as easily as any Brompton bag, but that is the result of a great deal of work.

"The battery connection to the bike has to be permanently engaged," explains Carley-Smith, "so our German partners developed a magnetic connector that can move on the bottom of the bag, meaning it can handle cobbles and potholes without disengaging. The cover over the connecter on the bike is not to keep it dry but to keep it clean: magnetic dirt is a thing, we discovered!"

Most users will never know the hours that went into developing a cover that can be flipped out of the way by the battery bag as it is fitted, but it's the sort of detail that delights and is absolutely consistent with the Brompton ethos. It will make your life easier, without you even realising it.

And designing a complex machine that is simple on the surface was essential in creating the Brompton Electric.

"One of the reasons it doesn't have a display with loads of functions on the handlebar is because simplicity was key from the off," confirms Carleyadams. "But there is a Bluetooth module in there that will talk to your phone, and there will be an app so you can add all that functionality to the phone. But most of our customers want super clean, super simple.

"Initially we weren't even going to have three assistance modes, although I think we got the balance right with that. I think Bosch had 12 at one point."

As for maintenance: "We have a diagnostic kit that works the same way as your car, so the bike shop will plug it in, swap out the parts the same day and away you go. They will then send the parts to us so we can work out what really went wrong. This is a tool for living, you can't take it out of action for three weeks."

The investment in this technology is clearly significant, but Brompton CEO Will Butler-Adams is adamant it will prove worthwhile:

"My belief is that in 15 years time you’ll have purists still riding regular bikes, but we’re not selling bikes in cities to cyclists, we’re selling them to urbanites as a useful tool to make life easier, give them freedom and make them happy. And this e-bike gives you the ability to get some exercise whizzing across your city, but does it in a way that gives you even more freedom to go further.

"We as a company are going to have to change a bit, because the speed at which this technology is moving, versus the speed bicycle technology has been moving, is going to be a lot faster. So we are going to have to innovate faster and faster."

"We’re unusual in being a bike company with technology as part of the company," adds Carleysmith, "most others buy the technology in. Owning the tech means we get to dictate terms, but it also means we have to keep pace."

The Brompton Electric is currently only available to pre-order for UK residents, excluding Northern Ireland. Once you’ve reserved your bike, you’ll be able to choose your options and dealer to collect from when you’re invited to make your final purchase. Prices range from £2,595 to £2,755.

The first bikes are due to be ready for delivery in the UK from early 2018 and then in "selected countries in Europe soon after". More info on Brompton's site.

This isn't the only folding ebike we’ve spent time with — the Tern Vektron really impressed us with its ‘regular’ Bosch motor and powerful disc brakes, but it was hard to swallow the 21.6kg weight and £3,000 price tag. Maybe a head-to-head is due in the coming months?

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