How to Convert Any Bike to Electric: Complete Step-by-Step Guide

You can turn almost any bicycle into an electric bike using a conversion kit, typically costing $300–$1,500. The process involves selecting the right kit type (hub motor or mid-drive), checking compatibility with your bike’s frame and brakes, then methodically installing the motor, battery, wiring, and display. This guide covers every step from tool preparation to the first test ride, including common pitfalls that can save you hours of rework.

Conversion Kit Types: Hub Motor vs. Mid-Drive

The biggest decision is which motor style fits your riding needs and mechanical comfort level. The table below compares the two main categories.

Feature	Hub Motor (Geared or Direct Drive)	Mid-Drive (e.g., Bafang BBS02/BBSHD)
Installation difficulty	Moderate – replaces rear wheel, no drivetrain changes	Higher – requires bottom bracket removal and crank tooling
Weight distribution	Adds weight to rear wheel	Centers weight near bottom bracket
Hill climbing	Good with geared hubs (more torque); direct drive struggles	Excellent – uses bike’s gears to multiply torque
Efficiency on flats	Direct drive is efficient at speed; geared hubs are balanced	Slightly less efficient at high RPM but still good
Bike compatibility	Requires correct dropout width (usually 135–145 mm) and wheel size	Requires a compatible bottom bracket shell (usually 68–73 mm BSA)
Typical power range	250W–1500W	250W–1000W (BBS02) or 1000W–1500W (BBSHD)
Best for	Commuters, flat terrain, easy install	Mountain biking, steep hills, cargo loads

Which to choose? If you want a straightforward swap and ride mostly paved roads, a hub motor kit like the Varstrom Ebike Conversion Kit (48V 500W/750W, compatible with 20″–700C wheels) is a strong start. For steep hills or technical trails, a mid-drive kit gives you better torque control because the motor leverages your bike’s gears. If you carry heavy loads, the mid-drive’s ability to keep the motor in its efficient RPM range while the bike’s drivetrain handles torque multiplication makes cargo conversions noticeably more capable.

Tools and Parts You’ll Need

Before starting, gather everything to avoid mid-project stops.

Essential tools:
– Set of metric Allen keys (3–8 mm)
– Torque wrench (for critical bolts)
– Crank puller (for mid-drive installation)
– Bottom bracket tool (for removing old BB)
– Cable cutters and wire strippers
– Zip ties and electrical tape
– Tire levers (if swapping tires)
– Multimeter (for verifying connections)

Parts included in a typical kit:
– Motor wheel or motor unit (hub or mid-drive)
– Controller
– Throttle or pedal-assist sensor
– Display panel
– Wiring harness
– Battery and charger (sold separately or as bundle)

Optional but recommended:
– A battery bag to securely mount the battery inside the triangle – the Cloudpower Ebike Battery Bag fits 24V–72V triangle batteries and keeps them stable during rides.
– Brake lever sensors (if your kit doesn’t include them) – they cut motor power when you brake.

Concrete mechanism: Without brake sensors, the motor can continue pushing against your braking force, especially on a steep downhill, causing the caliper to overheat and fade. The sensor interrupts the motor circuit the moment you squeeze the lever, so the mechanical brake does all the stopping work.

Preparing the Bike and Removing Components

Removing the Rear Wheel (Hub Motor Kits)

1. Shift your chain onto the smallest rear cog.
2. Disconnect the rear brake (disc caliper or V-brake cable).
3. Remove the axle nuts or quick-release skewer.
4. Slide the wheel out. For cassette-style hubs, you’ll need to transfer your existing cassette (or freewheel) to the new motor wheel – most hub kits come with a cassette adapter.

Removing the Bottom Bracket (Mid-Drive Kits)

1. Remove the cranks using a crank puller.
2. Use a bottom bracket tool to unscrew the existing BB unit. Measure the shell width (commonly 68 mm or 73 mm) – your motor’s bracket must match.
3. Clean the threads and apply anti-seize compound before installing the motor’s bottom bracket adapter.

Concrete mechanism: Mid-drive motors multiply torque through your bike’s gears, so a proper bottom bracket fit is critical. Even 1 mm of misalignment can cause the motor to slip or damage the shell threads. If you’re using a mid-drive on a steel frame that wasn’t faced at the factory, the shell may need re-facing for the flanges to sit flat – a bike shop can do this for about $30.

Installing the Motor

Hub Motor Installation

• Slide the motor wheel into the dropouts. Ensure the axle flats align with the dropout slots.
• Install torque washers or anti-rotation washers (included in most kits) to prevent the axle from spinning under load.
• Tighten axle nuts to manufacturer specification (usually 25–35 Nm). Over-tightening can crack the motor casing.
• Reattach the brake caliper and adjust so the rotor runs true.

Mid-Drive Installation

• Bolt the motor unit onto the bottom bracket adapter. Use the supplied lock ring to secure it.
• Reinstall the cranks with the included crank arms (often longer to clear the motor housing).
• Route the motor cable along the down tube, securing with zip ties.

Concrete mechanism: A loose hub motor axle can rotate, ripping out the power wires. Torque washers convert the axle’s turning force into a pinch grip on the dropout, preventing that failure. Check the washers by hand after tightening – there should be no rotational play.

Mounting the Battery

Battery placement affects handling and safety. The most common positions:

• Triangle bag – keeps weight low and central. The Cloudpower Ebike Battery Bag straps securely inside the frame triangle and works with batteries from 24V to 72V.
• Rack mount – fits on a rear carrier but adds weight behind the seat; good for pannier-balanced loads.
• Water bottle mount – small batteries (≤ 36V/10Ah) only; limited range.

Secure the battery firmly. Use rubber padding to prevent vibration. Route the battery cable away from the chain and brake rotor.

Concrete mechanism: Battery capacity (Wh = voltage × amp-hours) directly determines range. A 48V/14Ah pack (672 Wh) on a 500W motor typically gives 20–40 miles of pedal-assisted range, depending on terrain and rider weight. For commuting, aim for at least 500 Wh. If you often ride in cold weather (below 40°F), capacity drops by roughly 20% – plan your battery size accordingly.

Wiring and Display Setup

1. Connect the controller to the motor, battery, throttle/PAS sensor, and display. Most kits use color-coded bullet connectors or waterproof plugs.
2. Mount the display on the handlebar within easy view. Common displays show speed, battery level, assist level, and odometer.
3. Install the throttle (if included) on the right handlebar side.
4. Run the wires along the frame, using zip ties every 6–8 inches. Avoid sharp bends near the headset.
5. Install brake sensors – either hydraulic (screw-on) or mechanical (inline with brake cable). These cut motor power when you brake, which is a legal requirement in most e-bike classes.

Concrete mechanism: An inline brake sensor works by interrupting the circuit when the lever is pulled. If your kit lacks these, you can add aftermarket sensors for about $15 – a cheap way to avoid legal trouble and improve safety.

Testing and Troubleshooting

Before your first ride, perform these checks:

• Power on – turn on the battery and display. The display should light up.
• Throttle test – with the bike on a stand, gently twist the throttle. The wheel should spin smoothly. Listen for grinding noises (indicates misaligned motor or loose magnets).
• Pedal-assist test – pedal forward; the motor should engage within half a crank rotation.
• Brake cutoff test – squeeze either brake lever; the motor should stop instantly.
• Walk the bike – check that no cables catch on spokes or chain.

Verification step for the brake cutoff: After squeezing the brake, release it and confirm the motor re-engages within one second. If the motor stays off, the sensor may be stuck closed or the wiring is shorted – fix this before riding because you’ll have no power on the next pedal stroke.

Common failures and fixes:

Symptom	Likely Cause	Quick Fix
Display won’t power on	Battery switch off, loose discharge connector	Check battery voltage; reseat all connectors
Motor stutters or jerks	Loose phase wire connection	Inspect bullet connectors for corrosion or partial pull-out
No pedal assist	PAS sensor gap too large or magnet misaligned	Move sensor closer to chainring magnet (1–2 mm gap)
Battery drains fast	High assist level, cold weather, or stale cells	Use lower assist; store battery above 50°F; test capacity with multimeter

Concrete mechanism: A rattling chain or skipping gears after conversion often means the chainline is off. Mid-drive motors add width, so you may need to add a chain guide or adjust the derailleur limit screws. Ignoring this can snap a chain mid-ride – at speed, that means a sudden loss of pedal power and potential crash.

Time and Cost Estimate

Item	Time	Cost Range
Choosing a kit and ordering	1–3 days	$300–$1,200
Tool gathering	30 min	$0–$50 (if you own basic tools)
Bicycle prep	15–45 min	$0
Motor installation	1–3 hours (hub) / 2–4 hours (mid-drive)	—
Battery mount and wiring	1–2 hours	—
Display and sensor setup	30 min	—
Testing and adjustments	30 min–1 hour	—
Total (without unforeseen issues)	4–8 hours	$300–$1,500

Unforeseen issues – like needing a different freewheel tool or a longer brake cable – can add an hour or two. Plan for a full afternoon.

Frequently Asked Questions

Can I convert any bike, including a trike?
Yes, as long as the frame has standard dropouts or a bottom bracket compatible with the kit. Adult trikes like the EMOJO Electric Tricycle already come electrified, but a manual trike can also be converted using a front or rear hub motor, depending on axle width.

Do I need a special battery for my conversion kit?
You need a battery that matches the controller’s voltage (e.g., 36V or 48V) and can deliver the required continuous current (typically 15–30A). Lithium-ion packs are standard; avoid lead-acid batteries due to weight and poor lifespan.

Will my bike still work as a normal bike if the battery dies?
Yes, with a hub motor you’ll feel a slight drag from the internal gears, but it’s still peddalable. Mid-drive systems have almost no drag when unpowered.

Does a conversion affect my bike’s warranty?
Yes. Installing a motor typically voids the original manufacturer’s warranty on the frame and drivetrain. Check your bike’s warranty terms before proceeding.

What e-bike class will my conversion be?
Most hub motor kits can be programmed for Class 1 (20 mph, pedal-assist only) or Class 2 (20 mph, throttle). Mid-drive kits often support Class 3 (28 mph). You must set the speed limit in the display settings to comply with local laws.

Explore This Topic

• Back to Conversion Kits
• Back to E-Bike Conversion Kits

Related guides in this cluster:
– How to Install a Front Hub Motor Conversion Kit: Step-by-Step Guide
– How to Install a Rear Hub Motor Conversion Kit: Step-by-Step Guide
– How to Choose a Donor Bike for E-Bike Conversion: What Makes a Good Candidate
– E-Bike Conversion Tools Checklist: Everything You Need Before Starting