Electric Motor Bafang BBS02B 750W: From Bicycle to E-Bike!

Today, I’ll share the story of how I built a winter bike, and not just any bike, but one with a motor. The bike was built on the frame of a Cube AMS 100 full-suspension model with 26″ wheels. I decided not to title this review “Anatomy…” as I did with my previous in-depth reviews since the topic of an electric bike is entirely new to me. Let’s get acquainted with the e-bike conversion kit together!

Introduction

Disclaimer

Some may find my choices odd or the pricing debatable, but I made decisions based on my preferences.
This review is simply a story about my purchase and my personal experience with the product.

I own a decent MTB bike. It’s carbon and rigid with 27.5″ wheels. I’ve written about it before.
However, riding it in winter is challenging—plowing through snow takes a lot of effort.
After saving some money, I decided to upgrade an old bike for winter riding and to experience the new sensation of riding with a motor.

Why stick with 26″ wheels?

After all, marketers have been actively phasing out this wheel size. Nowadays, it’s nearly impossible to find quality new bikes with 26″ wheels.
There are two reasons for my choice:

1. My modest height of 170 cm.
2. Most importantly, I still have a durable, full set of 26″ wheels from my previous bike (a significant cost-saving factor).

Of course, it’s a bit inconvenient to store two sets of tires at home.

Component Selection

Bicycle motors come in two main types: electric and gasoline. Gasoline motors are not an option for apartment dwellers.

Electric bicycle motors are broadly categorized into:

• Hub Motors, which can be either geared or gearless.
• Mid-Drive Motors (installed in place of the pedal axle).

Advantages of a mid-drive motor compared to a hub motor

Starting with installation

• No need to replace or respoke wheels; the motor is installed in the bottom bracket.
• Compact, waterproof connectors prevent incorrect connections.
• The controller is integrated into the motor, so there’s no need to find a place for it.
• No dropout reinforcements are required, making it compatible with all dropout types (including thru-axles).

During operation, an e-bike with a mid-drive motor has several advantages over hub motors

• Suspension performance is unaffected since the wheels remain lightweight.
• If the battery runs out, pedaling feels just like on a regular bike because the motor doesn’t add resistance to the rotating parts (on muscle power, most effort goes into spinning the wheels, and lighter wheels mean less effort).
• Standard spokes and rims last longer as there’s no “weight in the wheel” (motor) causing damaging stress.
• Gear selection becomes road-adaptive: on loose terrain, in forests, or steep climbs, you can choose a low gear for confident and efficient movement, while in the city, you can seamlessly join traffic with a higher gear.
• The motor is discreet, similar to a low-powered geared hub motor, but much more powerful on trails and climbs than even a 1000W hub motor due to the ability to use gears.
• Wheels can still be easily removed for tube patching or replacement.

Of course, there are drawbacks to this setup, but we’ll discuss them at the end of the review after some real-world usage.

What about branded bikes with mid-drive motors?

They come with two significant disadvantages: exorbitant prices and software speed limits of 25 km/h (due to EU standards and traffic regulations).

On the Chinese market, regulations are more relaxed. Bafang/8FUN dominates here, and I chose from their offerings.

I opted for the Bafang BBS02B 750W motor paired with a 48V battery.

The BBSHD 1 kW version is certainly more powerful, but:

• It’s more expensive (~$1000).
• Larger in size.
• Nearly 2 kg heavier.
• Plus, you still need to handle those extra 150W with your legs, so I decided on the 750W version—a balanced choice of power, weight, and cost.

Here’s a video comparison with the 1 kW version.

And now for a budget-friendly alternative for those who think it’s too pricey:

Motor Bafang BBS02B

The Bafang BBS02B motor is not new to the market, and there’s a wealth of detailed discussions about it on the electric transport forums.

Motor Specifications

Motor

• The “B” at the end of the BBS02B model indicates an upgraded controller with IRFB3077 MOSFET transistors.
• My version is designed for a 68-73 mm bottom bracket, though a version for fat bikes with a 100-120 mm bottom bracket is also available.
• The gray flange with five threaded holes is used to mount the front chainring:
  • The chainring rotates independently of the pedals.
  • Crank arm attachment uses a square taper system.
  • There is a thread at the end of the bottom bracket axle for securing the motor.

Cables from the Motor

The motor comes with five wires:

1. Power supply for the battery.
2. Connector for the speed sensor.
3. Connector for the gear shift sensor.
4. Connector for the splitter, which connects to all other components.
5. Wires for a 6V headlight.

Splitter

The splitter connects to:

• Control screen for the controller.
• Brake cut-off sensors (2 pcs.).
• Throttle handle.

All connectors are rubberized, fit tightly, and include guides and arrows, making incorrect connections virtually impossible. The design is very thoughtful.

Motor Weight

The motor’s weight is optimized for its power and configuration.

Controller

The integrated controller is sealed with a compound and appears as follows:

• The design ensures durability and reliability.

Additional Motor Features

• USB Cable: For fine-tuning the controller.
• Gear Shift Sensor: Optional, it disables the motor when shifting gears on the cassette, reducing wear on the chain and cassette.

Battery

Battery form factors for an electric bike vary:

• Rear rack mount
• Seat post mount
• Frame triangle mount
• Bottle cage mount in the frame (my choice).

Alternatively, you can buy a battery case and assemble your own pack using 18650 cells and a BMS board.

Battery from the kit

Specifications

• Type: Lithium-ion battery, 624 Wh (48V, 13Ah).
• Cells: 4.2V 18650, 2600mAh, 1.5C discharge.
• Configuration: 13S5P (65 cells).
• Continuous discharge current: 20A.
• Maximum discharge current: 40A.
• Weight: 4 kg.
• Range: Up to 45 km (with 750W motor).
• BMS: Includes charge balancing, overheat protection, undervoltage protection, and cutoff mechanisms.
• Charger: 48V, 2A.
• Lifespan: Over 800 cycles.
• Charge temperature: 0–45°C.
• Discharge temperature: -20–65°C.

A larger capacity option (48V, 17.5Ah) is also available for extended range.

Design and Features

• Size and Mount: The battery mounts securely to the frame using a DIN rail-based steel base plate.
• Connector: Anderson power connector with a generously long cable.
• Charge Indicator: A four-segment LED indicator shows battery charge level.
• Charging Port: Covered with a rubber plug for protection.
• Master Switch: Tiny and not particularly robust.

Unfortunately, this model lacks a USB 5V 2A port for powering devices, which would have been a nice addition.

Security and Weight

• Equipped with a lock and two keys for theft protection.
• Battery weight is 4 kg.
• Mounted on the frame with two M5 bolts, but additional support with straps is recommended.

Battery Pack Assembly

The battery is built using 18650 cells. In this case:

• The cells used (Dynabat MX18650-26P) are not ideal for cold weather, unlike branded Samsung cells.

Charger

• Charge Time: 5–6 hours.
• Heat: The charger gets quite warm during operation.
• Specifications:
  • Standard connectors.
  • Power consumption of about 100W during charging.
  • Full charge uses approximately 0.4 kWh in 5 hours.

Cost Efficiency

• Electricity cost for a full charge: ~3.6 rubles (based on 1 kWh = 3.60 RUB).
• For comparison, driving 50 km in a car requires ~4 liters of A-95 gasoline, costing ~180 rubles (45 RUB/liter).

This highlights the substantial cost savings of using an electric bike over a car for the same distance.

Other Components of the Kit

Another key element of the bike electrification kit is the motor controller display panel.

Control Panel (C965)

Specifications

• Display: LCD.
• Voltage Compatibility: 24/36/48V.
• PAS Support: Modes 0–3/0–5/0–9.
• Protocol: UART.
• Dimensions: 107x58x70 mm.
• Handlebar Fit: Ø22.2/25.4/31.8 mm.
• Backlight: Yes.
• Protection: IP65 (dust and water-resistant).

Displayed Information

• Current speed (km/h).
• Maximum speed (km/h).
• Average speed (km/h).
• Trip duration.
• Trip distance.
• Odometer.
• Battery level.
• Error codes.

Advanced Panel Version

A version with a color display is available for $89.90, compared to $56 for my monochrome C965. The advanced model also includes a smartphone charging port, but I didn’t find it worth the extra cost.

My Version (C965)

• Comes with mounting rings for various handlebar diameters.
• The control buttons are simple and mounted on the left-hand side.
  • Buttons are small and hard to press with gloves in winter.

Functions and Buttons

1. Power Button
   • Long press: Turns the screen and controller on/off.
   • Short press: Cycles through trip data (distance, duration, average speed, max speed, etc.).
2. + / – Buttons
   • Adjust the pedal assist (PAS) level:
     • My setup includes levels 0, 1, 2, 3 (other options include 1–5 or 1–9).
   • Long press “+”: Activates the headlight.
   • Long press “-“: Engages P mode (pedestrian assist) where the bike rolls at 5–6 km/h.
3. Menu Access Press “+” and “-” simultaneously to enter the menu.

Menu Options

• Reset trip computer data.
• Adjust screen brightness.
• Auto power-off settings.
• Maintenance reminders.

Engineering Menu

• Access via a password (“0512”).
• Adjust wheel diameter.
• Remove or set speed limits.

Note: The speed reading on the panel is typically 1–2 km/h higher than GPS measurements.

Additional Kit Components

Crank Arms

• Square taper attachment.
• Requires a crank puller tool for removal and maintenance.

Chainring Options

• My setup uses a 44-tooth chainring:
  • Includes offset for optimal chain alignment.
  • Comes with optional plastic guard for added protection.

Motor and Crank Mounts

• Pre-applied thread locker where necessary.

Throttle Grip

• Mounted on the right-hand side.
• Downsides:
  • Takes up significant space on the handlebar.
  • Feels wide and bulky.

Speed Sensor

• Operates like a traditional bike computer sensor:
  • Magnet and reed switch mechanism.

Brake Levers for Mechanical Brakes

• Oversized levers, resembling motorcycle-style levers.

Alternative for Hydraulic Brakes

• Additional hydraulic brake sensors can be purchased ($18).
  • Installed to cut motor power immediately when the brake lever is pressed.
  • My sensors are not yet installed due to compatibility issues with my Avid Elixir brakes but are essential for safety and to reduce drivetrain wear.

Motor Installation Wrench

• Build: Laser-cut from 4mm black steel plate.
• Usage:
  • Functional but inconvenient due to lack of an angled grip for easier access.
  • Sold separately for $15, which feels overpriced for its basic design.

These components, while not perfect, provide a comprehensive kit to transform a standard bike into a functional electric one.

Bike Assembly

The motor installation process is well-documented in several video guides, such as [this one (video link needed)]. Below is an overview of my personal experience during the assembly:

Frame Preparation

• Before installation, all frame bearings were cleaned and re-greased.
• The fork and motor were installed next.

Motor Mounting

1. Chain Drop Protection:
   • Retained the front derailleur mount to serve as a chain guide and prevent chain drops.
2. Q-Factor Issue:
   • The pedal Q-factor shifted noticeably to the right due to the motor’s design.
   • It’s clear that with more effort, the right crank could have been positioned at least 2 cm closer to the centerline. A missed opportunity by the Chinese engineers.

Bottom Bracket Fit

• My Cube bike has a 73 mm bottom bracket.
• The motor’s mounting kit couldn’t fully accommodate this width:
  • The second securing nut couldn’t be fully threaded on due to insufficient thread length.

Motor Mounting Flaws

• The motor relies on friction between the bracket, the bottom bracket, and the nut to resist rotation.
• Issue:
  • Initially, with one nut, the motor rotated.
  • Even after applying thread-locker to the nut, the motor rotated again under vibration.
• Solution:
  • I fabricated a custom mounting bracket to provide additional support.

Final Mounting Solution

• The custom bracket prevents motor rotation effectively.

Ground Clearance

• With the motor installed, the bike’s clearance reduced significantly:
  • New clearance: 24 cm (using 26″ Schwalbe Nobby Nic 2.25″ tires, inflated to 1 bar).

Bike Weight

• Total weight: 22 kg.
  • Heavy for a regular bike, but reasonable for an e-bike.
  • Comparable to budget fat bikes or low-end steel bikes, which people ride without issue.

Electrical System Setup

Cable Connections

• All electrical cables were connected securely and routed for minimal interference.

No-Load Current Measurements

• Idle current draw was measured.
• Max working current: ~15 A.

Lighting Setup

Stock Headlight

• The seller offered a headlight for $20.
  • It looked unimpressive and overpriced.

Alternative Solution

• I repurposed an existing USB-powered bike light:
  • Cut off the USB connector.
  • Soldered spade connectors to match the motor’s 6V power supply.
• Result:
  • Functional, sufficient lighting powered directly by the motor.
  • Eliminates the need for additional batteries.

The assembly process was straightforward but revealed areas where the kit could be improved, particularly in motor mounting and design. However, with some custom modifications and creative solutions, the bike became a functional and practical e-bike for winter riding.Conclusion and

ImpressionsKit Features

At temperatures around -10°C, the battery capacity drops significantly, reducing the range to 30 km. For winter use, it’s recommended to choose LiFePO4 batteries, but they are more expensive.

Noise of the Bottom Bracket Motor

I expected more noise, but in practice, the sound of the gearbox is noticeably quieter than the sound of the tires. It’s definitely not as loud as an internal combustion engine.

Integrated Controller

This solution has both advantages (compactness) and disadvantages (limited customization options).

Throttle:

The full throttle response is instantaneous. Smooth control is only available after reprogramming the motor.

Conclusion and Impressions

Kit Features

• Noise of the Bottom Bracket Motor:
  • I expected more noise, but in practice, the sound of the gearbox is noticeably quieter than the sound of the tires. It’s definitely not as loud as an internal combustion engine.
• Integrated Controller:
  • This solution has both advantages (compactness) and disadvantages (limited customization options).
• Throttle:
  • The full throttle response is instantaneous. Smooth control is only available after reprogramming the motor.
• Battery Performance in Winter:
  • At temperatures around -10°C, the battery capacity drops significantly, reducing the range to 30 km. For winter use, it’s recommended to choose LiFePO4 batteries, but they are more expensive.