E-Bike Conversion Kits: Safety, New Tech, and What UK Law Means for Riders (and Shops)

E-bike conversion kits have become huge news across the UK cycling scene, but with that popularity has come a fair bit of controversy—especially around safety, tech advancements, and what the law expects of both riders and shops. If you’re thinking about converting your bike to electric, or fitting kits for customers, it’s vital to know what you’re getting into. Here’s the state of play for 2025.

The Legal Framework for E-Bikes in the UK

If you want your converted e-bike to be road-legal in the UK, several rules apply—no matter whether your bike was born electric or built from a kit.

• Maximum motor power: 250W (watts)
• Pedal assist only: The motor should only provide assistance when you’re pedalling—no throttle-only mode allowed.
• Speed limit: Motor assistance must cut out at 15.5mph (25kph).
• Age restriction: Riders must be 14 or older.

Break these rules and, in the eyes of the law, you don’t have an e-bike anymore—you’ve got a moped or motorcycle, with all the red tape that comes with that (insurance, helmet, registration, possible licence and MOT).

But it doesn’t end there. Recent legal developments mean anyone fitting an e-bike conversion kit—especially a shop or mechanic—can actually become the manufacturer in the eyes of UK law. Under rules like the General Product Safety Regulations and the Supply of Machinery (Safety) Regulations, you’re on the hook for product safety and full legal liability, just like a factory turning out new bikes.

E-Bike Kit Safety: What’s Gone Wrong?

Conversion kit tech has come a long way, but not all products are created equal. Safety concerns have shot up the agenda after several high-profile scares:

• Non-compliant electrics: Last year, border officials blocked a batch of imported e-bike kits, where the safety features simply weren’t plugged in. Specifically, the sensors that make sure you’re actually pedalling (and not just being carried along at speed) and brake levers which should cut power to the motor weren’t connected. That meant the bike could run “full throttle” with no pedal input, and wouldn’t even cut the motor when you braked—completely illegal, and highly dangerous.
• ‘Motorcycle mode’: Some unsafe kits allow bikes to operate at speeds well above the legal limits, without the controls you’d expect on a moped—leading to serious crash risks.
• Poor battery quality: Budget batteries have caused fires and battery “thermal runaway” events, leading to new guidelines being issued in December 2024 for all lithium-ion e-bike batteries.

Battery Safety: What Do You Need to Know?

Lithium-ion batteries are the heart (and sometimes, the Achilles’ heel) of any e-bike. New government rules lay out clear, mandatory safety measures for all e-bike batteries sold in the UK (whether as a stand-alone item or bundled in a conversion kit):

• Batteries must have built-in protections to avoid overheating or short-circuiting.
• Clear labelling and quality control checks are now required.
• Importers, shops, and even online sellers are all responsible for ensuring batteries comply—no more passing the buck.

If you’re buying a kit, ask about the battery. Take extra care if it’s imported from outside the UK or Europe.

Legal Responsibilities: What Shops and Fitters Need to Know

The legal landscape shifted in March 2025, when UK trade bodies (the Bicycle Association and the Association of Cycle Traders) issued new, clear guidance for shops and businesses doing e-bike conversions:

• If you fit a conversion kit to a customer’s bike, you are legally the manufacturer of the finished e-bike.
• You must label the bike with your name and address (as the “manufacturer”). Shops are fully responsible for the safety of everything—from the frame to the electrics.
• If something goes wrong and there’s a crash, fire, or injury linked to how the kit was fitted, the shop could be legally liable.

The Office for Product Safety and Standards backs this up: If you convert a bike to electric, you’re on the hook for its safety—and for any damage or injuries caused by faulty kits or installation.

Why does this matter? Many smaller retailers and workshops aren’t set up to handle the kind of responsibilities (or the insurance requirements) this brings. It’s a stark warning that cutting corners, or using dodgy kits, can result in legal challenges as well as damage to reputation.

The 2025 Parliamentary Inquiry and the Industry Response

All of these risks have built up to a major political push: in April 2025, the All Party Parliamentary Group for Cycling & Walking launched an inquiry focused on “dangerous” e-bike conversion kits.

Key issues raised so far:

• Many unsafe kits are making their way into the country via online marketplaces, avoiding quality control.
• There’s a special concern for gig economy riders, who may take risks with unsafe or non-compliant bikes to earn more.
• Questions about whether safety rules are stifling the market (the UK lags well behind Germany and the Netherlands for e-bike adoption) versus protecting the public.

MPs are pushing for tighter, clearer rules that apply to everyone: manufacturers, shops, importers, and customers. Expect more enforcement, more awareness, and possibly more hoops to jump through if you’re converting bikes.

Enforcement: Who’s Checking, and What Are the Risks?

In theory, Trading Standards, Border Force, and local authorities have wide powers to seize unsafe products and prosecute sellers. In practice, the sheer volume of online imports, the technical nature of e-bike conversion, and limited budgets mean many risky kits still slip through.

• Shops are far more likely to be caught and held liable than individual home tinkerers.
• If a kit is found to break UK rules—because it’s too powerful, lacks required safety features, or is not labelled correctly—it can be confiscated, and retailers face stiff penalties.
• Remember: criminal sanctions apply if you’re found to be selling unsafe goods, or supplying batteries and kits that don’t comply with the law.

New Technology: What’s Changing in E-Bike Kits?

It’s not all doom and gloom! Conversion tech is getting better, not just safer:

• Smart sensors: New kits feature improved pedal detection and torque sensors, making the boost feel more natural and stopping the “on/off” jerkiness older kits suffered from.
• Battery improvements: Modern, UK-compliant batteries are safer, lighter, and offer longer ranges with built-in management systems.
• Integrated displays and apps: Many kits now come with smartphone connectivity, so you can monitor battery health, track journeys, and get real-time data.
• Efficient motor designs: Mid-drive motors (which drive the cranks, not the wheel) offer quieter, more powerful rides, with better weight distribution for handling UK hills and city streets.

Whether you’re a rider upgrading your own bike or a shop considering fitting conversion kits, sticking with reputable brands—not bargain imports—is the smart way forward.

So, What Should Riders and Shops Do Next?

If You’re a Rider:

• Only buy conversion kits and batteries from reputable UK or EU suppliers.
• Stick to kits that clearly meet UK power, speed, and pedal-assist laws.
• If you’re unsure, ask your local bike shop for advice or a professional fitting. They’ll know what’s safe and legal.
• Check that any kit and battery has the correct labelling and documentation—don’t risk your safety (or your insurance) for a cheap deal.

If You’re a Shop or Mechanic:

• Familiarise yourself with the new rules: fitting a kit now comes with serious legal responsibility.
• Check product safety documentation, especially for batteries and electrical components.
• If you’re not confident you can meet the safety and labelling requirements, it may be best to stick to supplying, not installing, conversion kits.
• Consider insurance and proper processes—just like you would when manufacturing a whole bike.

Closing Thoughts

E-bike conversions have never been more popular—or more closely watched by UK regulators. Safer technology is on the rise, but so are risks from unsafe imports and regulatory complexity. For riders, compliance and smart choices make all the difference. For shops, conversion now means signing up to much greater responsibility and exposure.

As the legal and technical side of e-bikes moves forward, the best advice is stick with trusted suppliers, follow the guidance, and never be afraid to ask for help. If you’re unsure where to start or want help making sure your e-bike is safe and legal, drop into GC Bike Repairs or get in touch at www.gcbikerepairs.com—we’re always happy to have a chat and keep Portsmouth’s riders happy (and legal).