48V Folding Electric Bike
HKM-4425939 Folding Electric Bike
The HKM-4425939 folds flat for the trunk or the train, then unfolds into a 250 W brushless e-bike with a 48 V 17.5 Ah pack (about 840 Wh) good for 28-34 mi per charge. Dual suspension and 20 in tires keep the ride calm over city streets and park paths, and app control puts speed, range, and assistance on your phone.
250 W Brushless Motor48 V 17.5 Ah / ~840 Wh28-34 mi Range20 in TiresDual SuspensionHydraulic Disc BrakesFolding FrameApp Control
Motor
250 W
Brushless DC rear hub
Battery
48 V 17.5 Ah
About 840 Wh lithium-ion
Top Speed
15.5 mph
25 km/h, assist dependent
Range
28-34 mi
45-55 km per charge
Tires
20 in
City-profile pneumatic tires
Load Capacity
265 lb
120 kg rider plus cargo
Overview
A folding e-bike lives or dies on convenience, and the HKM-4425939 is built around it. The aluminum frame folds compact enough to slide into a car boot, a camper, or a train vestibule, then unfolds in moments into a ready-to-ride 250 W machine. For commuters who mix rail and road, or apartment dwellers with no garage, that fold is the whole point.
Power comes from a 250 W brushless DC rear hub motor - sealed, quiet, and free of the carbon brushes that wear out in older designs. Output is tuned for smooth city riding and gentle grades rather than outright speed, with a top speed of 15.5 mph (25 km/h) that stays inside typical shared-path limits. The motor augments your pedalling progressively, so the bike feels like strong legs rather than a sudden shove.
Energy is stored in a 48 V 17.5 Ah lithium pack holding about 840 Wh, protected by an intelligent battery management system that watches cell voltage, temperature, and balance. Real-world range is 28-34 mi (45-55 km) per charge - the upper figure on flat pavement at moderate assist, the lower figure on hills, headwinds, or heavier use. The pack slides in and out for indoor charging, and the same battery runs the LED front light, so there are no separate cells to keep charged.
Key Features
250 W Brushless Rear Hub Motor
A sealed brushless DC motor with no carbon brushes to wear down, less heat build-up under load, and quiet running. The 250 W output has the headroom for flat commuting and gentle climbs at a steady pace rather than short bursts, and a top speed of 15.5 mph (25 km/h) that suits shared paths.
48 V 17.5 Ah Lithium Pack (About 840 Wh)
An intelligent battery management system continuously monitors cell voltage, temperature, and charge balance, and protects the pack against overcharge, over-discharge, short circuit, and thermal runaway. The pack is removable, so you can charge it indoors and leave the bike locked outside.
Dual Suspension, Front and Rear
A suspension fork and a rear shock handle the square-edged hits at each wheel while the high-volume tires damp everything smaller. Together they deliver most of the comfort of a full-suspension frame for the kind of potholes, kerbs, and park paths a city commute actually contains.
Hydraulic Disc Brakes, Front and Rear
Hydraulic disc brakes keep the friction surface clear of the spray thrown up by the tire, so stopping performance stays consistent in rain, mud, and dust where rim brakes fade. The rotor sheds heat quickly on long descents, and the calipers are straightforward to adjust with basic tools.
Smooth Multi-Speed Drivetrain
A matched drivetrain with indexed shifting gives clean, repeatable shifts across a range wide enough for low-speed starts and faster flat sections alike. Keeping the right cadence also keeps the motor in its efficient band, which directly protects range.
20 in Pneumatic Tires
The 20 in tires spread rider and bike weight across a generous contact patch, which smooths small obstacles and keeps the bike stable on pavement and light trail. The air volume works as natural suspension, absorbing chatter with none of the weight of a mechanical linkage.
LED Lighting Powered by the Main Pack
The front LED light draws from the main battery, so there are no separate cells to keep charged before an early start or a ride home in the dark. On unlit sections that is the difference between finishing a loop and turning back.
Folding Aluminum Frame
The aluminum alloy frame folds compact for the car boot, camper, or train vestibule, and resists corrosion season after season. Balanced geometry keeps the bike stable at speed and nimble when you are walking it folded.
Full Specifications
Model
HKM-4425939 | Folding Electric Bike
Frame Material
Aluminum alloy, corrosion resistant, folding geometry
Motor
250 W brushless DC rear hub motor, sealed against dust
System Voltage
48 V DC
Battery
48 V 17.5 Ah lithium-ion (about 840 Wh) with intelligent BMS
Charger
Input 110-240 V, 50-60 Hz; US and EU plug options
Charging Time
4-5 hours from empty to full
Battery Protection
BMS guards against overcharge, over-discharge, short circuit, and thermal runaway
Top Speed
15.5 mph (25 km/h), assist dependent
Range Per Charge
28-34 mi (45-55 km), varies with terrain and assist level
Climbing
Assisted climbing on city grades and ramps
Motor Efficiency
Brushless commutation runs cooler and needs no internal servicing
Drivetrain
Multi-speed drivetrain with indexed shifting
Brakes
Hydraulic disc brakes, front and rear
Suspension
Dual suspension, front and rear
Tires
20 in pneumatic, city-profile tires
Wheels
20 in rims with reinforced spokes
Saddle
Padded saddle with upright riding position for long-ride comfort
Display
Smart LCD with app control: speed, battery, assist level
Assist System
Multi-level pedal assist; app-configurable ride modes
Lighting
LED front light powered by the main battery
Load Capacity
265 lb (120 kg) rider plus cargo
Bike Weight
About 99 lb (45 kg) including battery
Package Size
1420 x 280 x 880 mm folded / boxed
Warranty
24 Months Warranty Service (parts and labor)
Battery, Range, and Charging
The 48 V 17.5 Ah pack stores about 840 Wh and is protected by an intelligent battery management system that continuously monitors cell voltage, temperature, and charge balance, guarding against overcharge, over-discharge, short circuit, and thermal runaway. The pack is removable, so you can charge it indoors while the bike stays locked outside.
Quoted range is 28-34 mi (45-55 km). Reaching the upper end means flat pavement, moderate assist levels, correct tire pressure, and a rider of average weight; gradient, headwind, and higher assist settings all move you toward the lower figure. Cooler temperatures temporarily reduce available capacity, which returns as the pack warms.
Tip: Store the pack at 40-80 percent charge in a cool, dry place when the bike will not be ridden for a while, and avoid routinely running it below 10 percent. Both habits measurably extend the usable life of lithium-ion cells.
The supplied smart charger accepts 110-240 V, 50-60 Hz and takes the pack from empty to full in 4-5 hours, which suits overnight charging. The BMS terminates charging automatically once the cells reach full voltage, so the pack can be left connected overnight without risk.
Daily Use & Care
- Check tire pressure before each ride and keep it within the range printed on the tire sidewall; correctly inflated tires are the single biggest factor in range and handling.
- Keep the chain clean and lightly lubricated. Grit ground into a dry chain wears the drivetrain far faster than the mileage alone suggests.
- Inspect the hydraulic brake pads monthly and take up lever slack at the barrel adjuster as they wear down.
- Check that the frame hinges and folding clamps are torqued to specification after the first week of riding; a folding mechanism sees more stress than a fixed frame.
- Rinse mud and grit off the frame, rotors, and drivetrain after wet rides, then dry the rotors with a few light brake applications.
- Store the battery at 40-80 percent charge in a cool, dry place whenever the bike will sit unused for more than a few days.
- Book an annual professional tune-up to check wheel true, hinge play, and drivetrain wear.
What's in the Box
- 1 x HKM-4425939 folding electric bike, largely pre-assembled
- 1 x 48 V 17.5 Ah lithium battery pack (about 840 Wh)
- 1 x Smart charger (110-240 V, 50-60 Hz)
- 2 x Battery keys
- 1 x Toolkit with hex wrenches and pedal spanner
- 1 x Pair of pedals with reflectors
- 1 x User manual and assembly guide
Frequently Asked Questions
How far does it go on a charge?+
28-34 mi (45-55 km). Rider weight, gradient, assist level, tire pressure, temperature, and wind all affect the number, roughly in that order. On flat pavement at moderate assist you should reach the upper end of the band; headwinds and hills move you toward the lower figure.
How long does a full charge take?+
4-5 hours from empty with the supplied smart charger (110-240 V, 50-60 Hz). The BMS stops charging automatically once the cells reach full voltage, so it is safe to leave the pack plugged in overnight.
Is it easy to fold and carry?+
The aluminum frame folds compact for a car boot, camper, or train vestibule, and the bike weighs about 99 lb (45 kg) with the battery in. One person can walk it folded, though the weight is worth respecting on stairs.
Can I ride it where I live?+
Top speed is 15.5 mph (25 km/h), which keeps the bike inside typical low-speed e-bike classes in many areas. Rules vary by location, so check local law before riding on public roads or paths.
What does app control do?+
The app shows speed, remaining battery, and assist level on your phone and lets you configure ride modes. The onboard LCD shows the same essentials at a glance without needing the phone.
How do the hydraulic disc brakes compare with rim brakes?+
Three practical advantages: the rotor sits away from the tire spray zone so wet performance stays consistent, it sheds heat better on long descents so there is less fade, and it does not wear the wheel rim.
Can I ride it with the motor switched off?+
Yes. Set the assist to zero or switch the system off entirely and the bike works as a conventional bicycle. It weighs more than a non-electric bike, so a steep climb takes real effort, but the gearing helps considerably.
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24 Months Warranty Service
The product is covered by a 24-month warranty from the delivery date against manufacturing defects. Coverage includes parts and labor; normal-wear items are excluded.
48V 17.5Ah~840 Wh Pack250 W MotorDual SuspensionFolding FrameApp ControlHydraulic DiscAluminum Frame
Why Choose the HKM-4425939
One Bike, Two Commutes
The fold turns a train-and-rail commute into a door-to-door trip: ride to the station, fold it small, and unfold for the last mile. Most owners end up using one bike where they used to need two.
Calm Over City Bumps
On potholes, kerbs, and park paths the advantage of dual suspension plus 20 in tires is not tread pattern - it is that the wheel stays composed over surfaces that would jar a rigid bike. That is what makes a daily commute bearable.
Assist That Follows Your Effort
The pedal-assist system scales the motor contribution to what you are already doing rather than delivering a sudden surge. It feels like strong legs, not like being pushed, which is why it suits newer e-bike riders.
Nothing Inside the Motor to Wear Out
Brushless commutation removes the carbon brushes that wear, heat, and eventually need replacing. The motor runs quietly, stays cooler under load, and needs no internal servicing across the life of the bike.
Aluminum That Stays Presentable
An aluminum alloy frame resists corrosion naturally, so winter salt and wet trails do not leave their mark the way they would on unprotected steel. It also keeps the bike light enough to lift folded onto a rack.
A Saddle Built for Distance
A padded saddle with an upright riding position reduces lower-back and shoulder strain on longer rides, and balanced geometry keeps the bike stable at speed without making low-speed manoeuvring heavy.
Controls & Indicators
Power Button
On the battery pack; hold to switch the system on and off
Assist Buttons
Up and down buttons (and the app) cycle through the pedal-assist levels
Trip Meter
Trip distance and cumulative odometer on the display
Speedometer
Live speed readout in mph, switchable to km/h
Battery Gauge
Remaining capacity indicator driven by the battery management system
Light Switch
Toggle the LED headlight from the control pod
Shifter
Indexed shifter for the multi-speed drivetrain
Pre-Ride Safety Checklist
- Set tire pressure for the ride ahead, within the range marked on the tire sidewall.
- Squeeze both brake levers and confirm the pads bite firmly well before the lever reaches the grip.
- Check the battery is seated, locked, and showing the capacity you expect on the display.
- Spin both wheels to confirm the rims run true and nothing rubs the pads or the frame.
- Check the folding hinges, stem bolts, and seat clamp are tight, and rock the bike with the front brake on to feel for play.
- Shift through the gears at low speed to confirm the drivetrain indexes cleanly in both directions.
- Select a low assist level for the first minute of riding until you have the feel of the power delivery.
- Wear a helmet, and add gloves and eye protection for longer trips.
Quick Troubleshooting
The motor will not engage.+
Confirm the display is on and showing capacity, the battery is locked in place, and both brake levers are fully released - the cut-off sensors disable the motor while a lever is pulled. Note any diagnostic code shown on the display before contacting support.
Range has dropped compared with when the bike was new.+
Check tire pressure first - a soft tire on tarmac is the single most common cause. Then consider temperature; cool conditions temporarily reduce capacity. If range is down sharply year-round after many cycles, the pack may be nearing the end of its life.
The brakes squeal or feel weak.+
Take up lever slack at the barrel adjuster as the pads wear. Squealing usually indicates contaminated or glazed pads - clean the rotor with brake cleaner and replace the pads in pairs if the noise continues.
The chain skips under hard pedalling.+
Either the drivetrain indexing has drifted or the chain and cassette are worn. Adjust the barrel adjuster a quarter turn at a time. If it skips only in the smallest cogs, replace the cassette together with the chain.
The bike feels vague or wanders at speed.+
Front tire pressure that is too low is the usual cause on a 20 in bike. Check pressure, then check for hinge play by rocking the bike with the front brake applied, and confirm the folding clamps are torqued correctly.
The display shows a diagnostic code and the system will not run.+
Switch the system off, wait 30 seconds, and switch it back on. If the code returns, note the exact code and the conditions that produced it, then contact support - codes map to specific faults in the controller, motor, sensor, or battery circuits.
Certifications & Standards
The HKM-4425939 is produced in a facility operating under an ISO 9001 quality management system. The lithium cells and the assembled pack carry the test documentation normally required for lithium-ion transport and sale.
- ISO 9001 - Quality management system certification of the manufacturing facility.
- UN38.3 - Battery transport safety testing, required for lithium-ion shipping by air, sea, and road.
- MSDS - Material Safety Data Sheet available for the battery pack on request.
Important Safety Notes
This bike reaches up to 15.5 mph and weighs around 99 lb before a rider is added, so braking distances are longer than on a conventional bicycle. Read the manual before the first ride, begin on a low assist level, and get a feel for the acceleration and stopping distance in an open area before riding in traffic or on technical terrain.
- Wear a helmet on every ride, and add gloves and eye protection for longer trips.
- Do not exceed the 265 lb (120 kg) load capacity, which includes the rider and all cargo.
- Check local law before riding on public roads or paths; a 250 W, 15.5 mph e-bike falls within typical low-speed e-bike classes in many areas, but rules vary.
- Bed the brake pads in with a series of progressive stops from moderate speed during the first rides.
- Do not submerge the bike or use a pressure washer on the motor, battery compartment, or bearings.
- Charge only with the supplied charger, indoors, at room temperature, on a non-flammable surface.
- Do not open, puncture, or modify the battery pack. Damaged lithium cells can vent and ignite.
- Reduce speed on wet surfaces, loose gravel, and descents. Tires add grip but do not remove the risk of a slide.
HKM-4425939 · 250 W brushless DC rear hub motor · 48 V 17.5 Ah lithium (about 840 Wh) · 15.5 mph (25 km/h) top speed · 28-34 mi (45-55 km) range · 20 in tires · dual suspension · hydraulic disc brakes · folding aluminum frame · app control · 265 lb (120 kg) load capacity. Specifications are provided for reference; actual performance varies with rider weight, terrain, tire pressure, temperature, and riding style. Range figures assume moderate pedal assist. This page describes the product only and is not legal advice regarding vehicle classification - confirm local regulations before riding on public roads or paths.
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