Koolux BK6S 4.0 Folding Electric Bike
SKU: B94949
SPEED15.5 Mph
RANGE28 Miles
MOTOR250W
BATTERY13Ah
CHARGING6-7 Hours
WEIGHT73 lbs
Adjustable Cycle Helmet£38.99
Front and Rear Light Set£44.99
In stock now, a similar model
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This Model Is Fully Compliant With UK Road Regulations
This bike is built to comply with UK Electrically Assisted Pedal Cycle (EAPC) regulations, meaning it can be used on public roads and cycle paths without registration, tax, or a licence. Motor assistance is limited to 250W and cuts off at 15.5 mph (25 km/h).
See UK LegislationThis one carries 624 Wh of battery. The maker quotes 28 mi; in mixed riding with some hills, expect nearer 21 mi. A full charge costs about £0.17. Across a year that is roughly £976.00 less than making the same journeys by car, so the bike pays for itself in about 10 months. Everything here is worked out from this bike's own specification. Estimates, not promises: the assumptions are printed underneath.
Range you can expect
| Low assist, flat roads | 28 mi |
|---|---|
| Mixed riding, some hills | 21 mi |
| Full assist, loaded or hilly | 15 mi |
| Riding time on a charge | 1 h 49 min |
What it costs to run
| A full charge | £0.17 |
|---|---|
| Every 100 miles | £0.62 |
| Electricity for a year | £14.00 |
| The same year by car | £990.00 |
| You keep | £976.00 |
| Pays for itself in | 10 months |
Worked out from the specification
| Battery energy | 624 Wh |
|---|---|
| Energy per mile | 22.3 Wh |
| Charger output | 2.2 A |
| Power to weight | 7.6 W/kg |
| You can carry | 265 lb |
Based on £0.245 per kWh, £0.45 per mile to run a small car, and 2,200 miles a year. Charging is costed at the socket, not at the battery.
Four-inch fat tyres and 624 watt hours, folding
The KOOLUX BK6S 4.0 runs 20 × 4 inch fat tyres on a 48V 624 Wh battery and folds, at £789.
250W and 15.5 mph: it meets the EAPC rules, so there is no licence, no tax and no registration.
What the 4.0 adds over the 3.0
Fifty pounds separates the two, and KOOLUX publishes what it buys.
- Four-inch fat tyres rather than three
- Forty-eight volts and 624 Wh rather than 36 volts and 468
- Sixteen pounds more weight, at 73 lbs
- The same claimed range, the same brakes, the same transmission
If you ride on tarmac and do not need the float of a four-inch tyre, the 3.0 does the same job for less.
Forty-eight volts and 624 watt hours
KOOLUX publishes the watt-hour figure, which is the only number that compares across voltages.
Higher voltage means fewer amps for the same power, so less heat in the controller. The charger is a 54.6V 2A unit and takes six to seven hours.
Twenty-eight to fifty-six miles
KOOLUX claims 45 to 90 km and our table carries the lower figure.
Fat tyres cost range, which is why the 4.0 claims the same distance as the 3.0 despite carrying a third more battery. The panel below turns the capacity into energy per mile so you can see where it goes.
The brakes are mechanical, and you should know that
Cable rather than hydraulic, front and rear.
On a 73 lb bike with fat tyres we would prefer hydraulic, and it is the line that gives us most pause on this sheet. They stop well and want the cable tension checking now and then, but write to us if braking is your priority and we will show you the alternatives.
KOOLUX publishes two weights, and we will not choose between them
The sheet reads "33.2/40 kg" without saying which is which.
Our table carries 73 lbs, the lower of the two. It is most likely the bike without its battery against the bike with it, but KOOLUX does not say so and we will not write it as though they did. Write to us before you order if the exact weight decides your purchase.
Before the first ride, and who it is for
Payload is 265 lbs, lower than 96% of our catalogue and modest for a fat-tyre machine of this size. A suspension fork at the front, an aluminium frame, Shimano 7-speed and an IP54 rating. No torque figure is published and that row stays empty below.
- Unfold and lock the frame and the stem, then check both again after the first hour
- Bed the two mechanical brakes in at walking pace and set the cable tension
- Check that tension again after the first ride
- Run the tyres soft for grip, firmer for range
- Allow six to seven hours for the first charge
Buy it if you ride on sand, grass or soft ground and the bike has to fold. That is exactly what the four-inch tyre is for, and it is the only reason to pay the fifty pounds over the 3.0.
- BRAND
- KOOLUX
- CATEGORY
- Folding
- MOTOR POWER
- 250W
- RANGE
- 28 Miles
- SPEED
- 15.5 Mph
- BATTERY
- 13Ah
- WEIGHT
- 73 lbs
- CHARGING TIME
- 6-7 Hours
- BRAKE SYSTEM
- Mechanical Brakes
- FRAME MATERIAL
- Aluminum Alloy
- MAXIMUM LOAD
- 265 lbs
- INPUT VOLTAGE
- 48V
- TIRE SIZE
- 20 inch
- TORQUE
- N/A
The Koolux BK6S 4.0 Folding Electric Bike states 250W, 28 Miles and 15.5 Mph, and below it is set against the DYU FF500 20 Inch Fat Tire Folding Electric Bike. Every figure the two disagree on is marked. Choose a different bike to compare it with whichever one you are also considering.
9 of 12 specifications differ. View DYU FF500 20 Inch Fat Tire Folding Electric Bike
- Is the KOOLUX BK6S 4.0 foldable?
- Yes, it features a foldable frame for easy storage and transport.
- Is the KOOLUX BK6S 4.0 suitable for off-road riding?
- Yes, the fat tires and suspension system provide excellent stability on rough terrain.
- Does the KOOLUX BK6S 4.0 offer long battery range?
- Yes, it is designed for extended riding distance and daily commuting.
- What are the benefits of the fat tires?
- Fat tires improve traction, comfort, and control on various road and trail conditions.
- Are the electric bikes brand new?
- Yes. All electric bikes sold by BikTron are brand new, factory-sealed, and sourced directly from authorised manufacturers and official distributors.
- How do I choose the right electric bike for me?
- Pick a bike based on how you plan to ride. City bikes are great for commuting, folding bikes work well if you need compact storage, mountain bikes handle hills and mixed terrain, and cargo bikes are ideal for carrying shopping or loads. If you are not sure, our Bike Quiz can help.
- Are the batteries original and certified?
- Yes. Every electric bike battery is brand new and original from the manufacturer, with full safety certification and performance testing.
- Are the bikes tested before shipping?
- Yes. Each e-bike goes through a quality check before dispatch, covering electronics, brakes, motor response, and battery performance.
- Do electric bikes come with a warranty?
- Yes. All electric bikes from BikTron include a manufacturer warranty. Duration depends on the brand and model. Most bikes include a 12-month warranty as standard.
- How long does delivery take?
- Standard UK delivery usually takes 2 to 7 business days. Remote areas may take a little longer. You will receive a tracking link by email once your order is dispatched.
- Which payment methods do you accept?
- We accept Visa, Mastercard, PayPal, Apple Pay, Google Pay, and Klarna buy-now-pay-later. All payments are processed securely.
- Can I return my electric bike?
- Yes. You can ride the bike and still return it. Tell us within 30 days of delivery and we book the courier and collect it from your door. Contact us first and we will guide you through the process.
- Do the bikes need assembly?
- Most electric bikes arrive 85 to 90 per cent pre-assembled. You will usually need to attach the handlebars, pedals, and adjust the seat. A basic tool set is often included.
- Are BikTron electric bikes legal to ride in the UK?
- Yes. All bikes sold by BikTron that meet UK EAPC rules (250W motor, max 15.5 mph assisted speed, pedal-assisted only) are fully road-legal. You do not need a licence, tax, or insurance to ride them on public roads. Riders must be at least 14 years old.
- What about the electric scooters?
- Those are different, and the law treats them differently. A privately owned e-scooter cannot legally be ridden on a public road, pavement or cycle lane in the UK, whoever sold it. We sell ours for private land use only, with the landowner's permission, and every scooter product page says so. If you want something you can ride to work, choose an electric bike.
Secure checkout and fast UK delivery on every order.
- Free standard UK delivery on most bikes — 2 to 7 business days
- Express delivery may be available on request
- Full tracking included with every order
- Pay securely with Visa, Mastercard, PayPal, Apple Pay, Google Pay, or Klarna
- 0% finance available through Klarna at checkout
Before you order:
- Delivery is to UK mainland addresses — some remote areas may have a small surcharge
- Most bikes arrive 85–90% pre-assembled and include basic tools for setup
- If you are unsure about sizing or specs, contact us before you buy
Full details at Payment & Shipping.
Simple and fair terms so you can buy with confidence.
- 30-day return window — if the bike is not right for you, send it back
- Ride it. It needs to come back clean, undamaged and complete, with the charger, tools and manual
- A refund or replacement is issued after we receive and check the return
Please note:
- For a change of mind we book the collection and deduct its cost from your refund, and we tell you the amount before we book it
- If we sent the wrong item or it arrived faulty, we cover return shipping in full
- All bikes include a 12-month manufacturer warranty as standard
Full details at Returns & Refunds and Warranty.
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