Brompton E-Conversion Kits: Top 5 Picks for Your Folding Bike

The Handlebar Battery Problem

Mounting 1-1.5kg on your handlebars fundamentally changes how a Brompton steers. The front-heavy weight distribution makes low-speed maneuvering less precise and affects the bike’s legendary nimble handling. You’ll adapt, but the trade-off is real.

Pedal Sensor Installation Reality

The Brompton-specific pedal sensor (extra cost) requires crank arm removal and careful alignment. The universal sensor works but sits exposed and vulnerable on the frame. Getting the 2mm gap correct between sensor and magnet disc requires patience and zip ties.

No Remote Control

Power adjustment happens on the battery itself, not via handlebar controls. This means reaching forward mid-ride to change assistance levels. The interface works but feels outdated compared to competitors with wireless remotes.

Service and Delivery Issues

Delivery timelines frequently extend beyond initial estimates. Customer service responses can take weeks, and warranty registration proves frustrating for some buyers. The kit itself works, but post-purchase support is inconsistent. Budget accordingly for potential delays and minimal hand-holding.

Integration and Fold Quality

The Boost system preserves the Brompton’s quick fold completely. The battery stays mounted during folding, and the weight distribution doesn’t compromise carrying. The wireless head unit communicates via Bluetooth, eliminating cable routing issues through the folding stem.

The Hub Gear Sacrifice

Installing the Boost rear hub motor eliminates Sturmey-Archer hub gears. Your Brompton becomes a two-speed (one gear plus the motor). For hilly areas, this means relying heavily on electric assistance. The derailleur remains functional, but you lose the versatility of internal hub gears.

Power Delivery Quirk

The motor’s power curve favors higher speeds. At low speeds on steep hills, assistance feels muted unless you press the Super Boost button. This button override works but requires constant thumb pressure, making sustained climbing awkward. The system excels on moderate inclines and flat terrain but struggles with steep gradients compared to competitors.

Battery Non-Removable for Charging

The battery charges in place, requiring you to bring the bike to the outlet. If you store your Brompton at work or lack convenient charging access, this becomes a daily inconvenience. Competitors offer removable batteries you can charge at your desk.

Range Expectations The 30km range suits short urban commutes perfectly. Daily 15km round trips leave comfortable battery margin. However, if your commute involves significant hills or you’re carrying cargo, expect closer to 20-25km before recharging.

Five Power Levels and Bluetooth Control

The handlebar boost button cycles through five assistance levels (20% intervals) with satisfying precision. The Bluetooth app provides battery monitoring, power customization, and firmware updates. The system’s sprocket movement sensor counts individual teeth for smooth, accurate power delivery.

Cadence vs Torque Sensing Trade-off

Cytronex uses cadence sensing rather than torque sensing. Assistance kicks in about half a second after pedaling starts and has a slight on/off character compared to torque-based systems. It’s smoother than cheap cadence sensors but not as seamlessly progressive as ARCC’s torque system.

Step-Over Height Increase

The battery’s central frame position raises step-over height noticeably. Shorter riders or those with mobility limitations need to evaluate this carefully. The battery can be removed quickly, dropping the bike to near-original weight for lifting onto trains.

Customer Support Excellence

Cytronex provides responsive, knowledgeable support. The Winchester shop offers personal service, and email responses arrive promptly with detailed technical answers. This level of support justifies part of the premium pricing.

Installation Simplicity

The F23 mounts directly onto Brompton’s standard bag hanger clip. Replace the front wheel, install the bracket, mount sensors, and you’re riding in 15-20 minutes. The battery detaches easily, reducing theft risk when parked.

The 45Nm Question

Byqee advertises 45Nm torque, matching more expensive kits. In practice, the motor handles moderate hills adequately but can’t match Cytronex or ARCC on sustained steep climbs. The 350W peak power (250W nominal) provides decent punch for urban riding but falls short in mountainous terrain.

Limited Track Record

Byqee’s relative newness means fewer long-term reliability reports exist. The company offers standard warranty coverage, but service network and replacement part availability remain question marks compared to established brands. Early adopters report satisfactory experiences, but multi-year durability data is sparse.

Optional Throttle Mode

Unlike most conversion kits, Byqee offers an optional thumb throttle. This provides walk-assist functionality and pure electric propulsion without pedaling. UK and EU regulations limit throttle-only operation to 6km/h (walking pace), but the feature adds versatility.

Torque Sensing and Automatic Mode

ARCC’s system uses both torque sensing and an inclinometer. The motor responds to pedal pressure instantly, and automatic mode adjusts assistance based on gradient changes. Seven power levels provide granular control, and the system feels closer to mid-drive quality than typical hub motors.

The Battery Capacity Problem

ARCC uses Bosch power tool batteries. The standard 144Wh (4Ah) battery provides only 7 miles range in hilly terrain. Upgrading to the 216Wh (6Ah) battery extends range to 20 miles but costs £200 extra. The 324Wh battery exists but must be purchased separately and adds significant weight. Compared to Cytronex’s 198Wh included battery with 40km range, ARCC’s base specification underwhelms.

Fiddly Button Controls

The Bluetooth controller features small buttons difficult to operate with gloves. In darkness, finding the correct button requires fumbling. The iPhone app provides an alternative interface but excludes Android users. Battery level indication uses color-coded LEDs rather than precise percentage display.

Front Luggage Block Compromise

The pod mounts where Brompton’s front luggage block normally sits. ARCC offers a bag adapter kit that integrates the battery into most Brompton bags, but this solution adds complexity and weight. You’re choosing between full luggage capacity and the ARCC system.

Five-Year Warranty ARCC backs the system with a five-year warranty and will honor remaining Brompton frame warranties on bikes they convert. This coverage is exceptional for conversion kits and reflects confidence in long-term durability.

Wet Weather Traction

Front-wheel drive systems can break traction on wet manhole covers or painted road markings when accelerating hard. Throttle control and smooth pedaling mitigate this, but rear-drive Boost eliminates the issue entirely by driving the weighted rear wheel.

The Conversion Math

Take a used C Line 12-speed (£750-£1,000) plus Cytronex kit (£1,145) = £1,895-£2,145 total. The official C Line Electric costs £3,150, meaning you save £1,005-£1,255 with a conversion kit.

However, the official model provides full warranty coverage, integrated design, dealer support network, and significantly better resale value. New riders often find the premium worthwhile, while experienced Brompton owners comfortable with DIY modifications benefit most from conversion savings.

Weight Reality Check

Official Brompton electrics add 4.7-5.6kg over their non-electric equivalents (P Line Electric adds 5.6kg, C Line Electric adds 5.3kg, G Line Electric adds 4.7kg).

Quality conversion kits add 2.4-3.9kg but use smaller batteries. Brompton’s 300-345Wh batteries provide genuine 40-72km range with predictable performance, while most conversion kit batteries (90-237Wh) deliver 15-40km.

You carry less weight with conversion kits but accept significantly reduced range and battery longevity questions.