On the road to electrification with the Swytch e-bike conversion kit

Electric bikes have been on the market for a number of years now. But thanks to increasing affordability, a pandemic induced cycling boom, and a growing appetite for more sustainable modes of transport, sales have snowballed in recent months. Indeed, according to the Bicycle Association – the trade body for the UK cycle industry – e-bike sales grew by 67 per cent in 2020 and are expected to triple by 2023.

Scrambling to tap into this growing market, bike manufacturers have introduced a wide range of different products: from budget electric commuter models through to high end mountain and road  bikes with car-sized price tags.

But the growing interest has also led to the emergence of a number of e-bike conversion kits that can be used to electrify much-loved existing bicycles and which potentially represent a more cost-effective and versatile solution than an entirely new machine.

The Engineer recently had an opportunity to try out one of the most talked about products in this emerging area: the Swytch kit, developed by London based e-mobility startup Swytch Technology ltd.

Consisting of a modified front wheel, pedal sensor system and handlebar mounted power pack – Swytch is claimed to be the smallest and lightest e-bike conversion kit on the market. What’s more, according to its developers, it’s compatible with any bike.

The product was invented in 2017 by electrical engineer Oliver Montague, who was inspired to develop his own system after having a crack at importing and selling off-the-shelf kits from China.

Frustrated by the variable quality of these devices and the non-existent customer service, Montague spotted a gap in the market for a well-designed, universal kit that could be backed up by a slick customer service operation and the concept for the Swytch kit was born.

Following a successful crowd funding campaign on Indiegogo, the product was launched in 2018 and sales have grown rapidly ever since. According to co-founder electrical engineer Dmitro Khroma the company - which now employs 35 people at its HQ in Hackney, East London - sold 20,000 units last year, and is on track to hit similar numbers this year.

Swytch has four key components: a power pack (which contains the lithium ion battery, controller and display), a quick release handlebar bracket for attaching the power pack to the bike, a custom built front wheel with an integrated hub motor, and a magnetic pedal sensor kit (consisting of a magnet that fits on the centre of the pedal crank and a sensor that attaches to the bike frame.) The power pack and connector were developed entirely in house, whist the motors are sourced from an external supplier. These motor and battery add around 3.5kg to the weight of a bike.

During use, the magnetic pedal sensor detects when you’re pedaling and sends a signal to the power pack which uses a bespoke control algorithm to determine how much power to supply based on factors including pedal cadence and acceleration. When you stop pedaling the motor stops spinning.

A simple display on the top of the power pack shows the battery level and allows the user to choose between five different power levels depending on how lazy or active you’re feeling. If you turn the system off entirely you can pedal as you would normally.

The 250W brushless hub motor generates 40Nm of torque (claimed to be enough to drag the average adult up a 30 per cent incline with light pedaling) whilst the 250Wh power pack gives a range of 35 or 50km depending on how much work you’re prepared to put in and which specification you go for (either the Eco or the higher capacity Pro). The system has a top speed of 15mph (24km/h) for UK customers and 20 mph for US customers.

Whilst Swytch isn’t the only conversion kit out there, Khroma believes that the elegance of the design coupled with an emphasis on customer service (including video calls with technicians) sets the product apart.  “The thing that separates us from a lot of companies is the level of service that we provide,” he said, “there are challenges to converting your bike, but we’ll be there every step of the way. We’re trying to make the experience as seamless as possible.”

Until now, the product’s most enthusiastic adopters have been formerly active  cyclists who - through old age, declining fitness or injury - are no longer able to conquer the hills of their glory days.  But according to Khroma the customer demographic is becoming broader all of the time.

Indeed, because of the pandemic the firm hasn’t yet had a serious chance to make an impact on the commuter market (where the technology has some major attractions) and the team is braced for a spike in this area as returning commuters seek out an alternative to crowded trains and buses.

Further into the future, Khroma said that the firm is eyeing up opportunities for other technologies and developments in what is becoming one of the mobility sector’s fastest moving areas.  “The e-bike industry is growing so rapidly,” he said.  “If you ‘re standing still you’re falling behind. What I’m excited about is being able to provide more alternatives to cars and buses…so we’re talking about new types of conversion kit, and even complete electric bikes.”

Prices range from £999 for a universal Eco kit through to £1500 for the Brompton Pro, a configuration designed specifically for the Brompton folding bike (see box out).

Set up and ride

To put the technology to the test, Jon Excell fitted a Brompton Pro Swytch kit to his trusty folding bike. 

Unless – like I did – you adopt the time-honoured approach of diving in without reading the instructions, assembling the Swytch kit (which requires you to fit a new front wheel, attach a power pack bracket, position the pedal sensor, and route an assortment of cables) is a relatively straightforward process, particularly if you take the firm up on the offer of a one-to-one video support call.

Even so, my more gung-ho approach was relatively hassle free, and the kit was up and running in just over an hour.

The trickiest part of the set-up is positioning the magnetic pedal sensor. Precise alignment between the frame mounted sensor and the pedal crank magnet array is key to ensuring that the system operates smoothly, and positioning the frame sensor required some judicious use of cable ties. In response to this relatively minor gripe, Swytch CTO Dmitro Khroma told The Engineer that the team is currently working on an alternative wireless, no fuss sensing method, akin to the Bluetooth cadence sensors already used by many serious cyclists.

With the bike up and running it was time to clip on the battery pack, select the highest power setting and put the technology to the test on the mean streets of Hertfordshire where – it has to be said – the Swytch kit didn’t disappoint.

The boost provided by the kit’s 250W motor – which kicks in after couple of seconds of pedaling – rapidly accelerates you up to a decent cycling speed without any effort at all. And once you’re cruising, the ride is so smooth and quiet that you initially begin to wonder whether it’s stopped working. Until - that is - you cruise past a lycra-clad road warrior without breaking a sweat.

The kit also performs admirably on reasonably steep hills where - although a little more pedaling effort is required - the 40Nm of torque helps you sail up ordinarily energy-sapping slopes.

What’s more, the battery pack and power management system hold up well in various different scenarios. A five mile pedal across London on full power used up just one of the five bars on the battery monitor, so it’s certainly a credible solution for a much longer ride (particularly if you’re using it for the commute and able to charge it up again at the office).

The system does add some weight to the bike (around 3.5 kg including the battery pack and wheel motor) as well as a bit of extra cabling but – in the case of the Brompton – the folding mechanism still works well, and the bike can still be lugged on and off public transport reasonably comfortably. It should also be added that if you are thinking of adding a Swytch, or any other e conversion kit, to a Brompton, then it will invalidate any remaining warranty.

In short though, Swytch is a well-designed, easy to install, and nice to use system, developed by an engaging bunch of UK engineers who are clearly passionate about their technology.  What’s not to like?