Ebike motors explained
Hanging from all e-bikes is a bulging black plastic cage housing some kind of magic that helps you go faster, travel further, and pedal longer. When I was looking at converting my bike to an e-bike I needed to know just which type of motor and battery would be best… so I spent numerous late nights researching (fueled by lots of coffee) and gathering intel from some of the industry’s leading brands and experts.
With this guide, I’m pretty confident I’ve been able to answer most of the common questions about ebike motors.
How do Ebike Motors Work?
If you’ve ever owned a bicycle with dynamo powered lights, you’ve already owned an electric-powered bike. Consider this: as you push your legs down and up on the bike’s pedals, you make the wheels rotate, which, in turn, causes the small dynamo (generator) mounted at the rear wheel to produce a small electric current that keeps your safety lamp lit as you ride in the dark.
Suppose you reversed the process. Imagine if you replaced the lamp with a massive battery. This battery would kick out steady electric currents and drive the small dynamo in the opposite direction. As the dynamo spins around like an electric motor, it would rotate your bike’s tire and make it move along without any pedaling effort on your end.
I know this example might sound a little bit far-fetched, but it’s more or less precisely how an electric bike works.
Allow me to elaborate by separating an e-bike’s motor into its key parts.
Brushless Ebike Motors
Unlike older electric motors that use a “brushed DC motor,” e-bikes use brushless DC motors or BLDC motors. In dated brushed motors, the brush is the device that conducts electricity inside the motor and serves as the intermediary between stationary wires and all other moving parts of the motor itself.
These motors have a problem, however. As the motors age due to repeated use, the brushes tend to wear away, get jammed up, or completely break down. They’re also occasionally prone to sparking and are noisy.
The brushless DC motor set-up used by e-bikes isn’t subject to any of these issues. The motors are essentially inverted, swapping places with the permanent magnets. What’s more – by alternating which electromagnets get energized at a time and sequentially changing them, a brushless motor then turns the shaft, which, in turn, propels the bike.
Ebike Controllers and Batteries
E-bike batteries are arguably the most vital part of an e-bike since they house all the power needed to drive you along. Typical e-bike batteries make about 30 – 50 volts and 10 amps of power. As such, they’ll give you a top speed of between 10 and 20 mph and a range of between 10 and 40 miles between charges (depending on the terrain you’re riding on.) With an ebike that is not only pedal assisted, but also has a throttle facility, you can extend the e-bike’s range by freewheeling or pedaling some of the time.
Now, once the electricity leaves your e-bike’s battery and heads to its motor, it makes a small pit-stop in between at the controller. As with all other electronic devices, the controller manages and regulates the amount of power delivered to the e-bike’s motor, thereby determining how fast it’ll spin.
Note, though, controllers are a little more complex on e-bikes, and the level of complexity depends on the level of assistance your e-bike model offers.
For example, if you’re feeling great and don’t need help riding, you can engage the “pedal only mode,” where the controller will send no power to the motor, and you’ll need to use your legs to do all the work.
If you notice a huge hill up ahead but do not feel like sweating it out, you might enter the “pedal-assist mode”, where both your legs and the motor will work together. The ratio of the machine to human power exerted in this case will depend on how hard you pedal and how much assistance you have set your ebike to give. The bottom line is both the motor and you will be working in tandem to spin your e-bike’s rear wheel.
Finally, assume you’re at the end of your ride and you’ve exhausted yourself. Now, you can sit back and engage the “electric-only mode.” This mode only works for ebikes that have a ‘throttle only’ facility. With this setting, you can even take your feet off the pedals and let the e-bike’s motor do all the dirty work for you. Your e-bike will essentially transform into a moped or electric scooter.
Most of the best e-bikes in the market also retail with a display mounted on their handlebars. These displays allow you to switch between the different modes and show you helpful info about your ride, like the amount of power left in your batteries, how far you’ve ridden, calories burnt, etc.
What are the different Types of ebike Motors?
The two common electric motors used in e-bikes today are mid-drive and hub motors. Mid-drive motors usually house the motor close to the mid-area of the e-bike itself, while hub motors house theirs at the mid-section of the e-bike wheel.
Also worth noting, while hub motor e-bikes have been leading in numbers for a while now, mid-drive models that transfer power from their motors to their rear wheels through the bikes’ chains have been gaining ground for the last two to three years.
So, mid-drive vs hub motors, which one is the best? Let’s find out.
Mid-Drive vs Hub Motor
In this section of the guide, I intend to highlight each motor’s upsides and downsides to help you pick the best one for your needs.
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Advantages of Ebike Hub Motor
The biggest advantage of hub motor e-bikes is the fact they need little to no maintenance efforts. Since all their motor components have been housed inside the casing, the independent drive system leaves you nothing you can maintain or mess with.
An enclosed motor system also implies chances of anything failing due to external factors are incredibly minimal.
Most importantly, Hub Motors retail in two types, geared hub and direct-drive hub motors. Direct-drive hub motors have no gears and directly connect the bike to the lowest RPM motor stator’s axle, whereas geared hub electric motors retail with internal planetary gears that reduce a higher RPM motor’s speed.
Which one is the best between the two? Well, geared hub electric motors have one major weakness, their gears. Over an extended usage period, the reinforced plastic gears will ultimately strip, and a gear tooth might break off.
Direct-drive hub motors, conversely, have nothing to wear out since they have no moving parts except their bearings. Provided their bearings do not wear down or rust out, a direct drive hub motor can virtually last an eternity.
Compared to a mid-drive motor, a hub motor also reduces miscellaneous bike maintenance issues. Since hub motors aren’t connected to e-bikes’ primary pedal drive systems, they do not add any more stress to the bike’s shifters or chain. This further implies they won’t make any of these parts wear out faster.
If anything, a hub motor allows your e-bikes chain to last longer by helping it sit idle whenever the motor is engaged.
If you prefer staying prepared for any issues that might arise amidst your bike riding sessions, a hub motor is still your best bet. Since hub motors and pedal drive systems have been completely separated, losing one doesn’t mean you won’t still go back on your bike. The e-bike’s hub motor fails for some reason? Pedal the bike. The chain breaks because you’re hitting the trail hard? Simply toss it in your backpack and use the electric power to get home (if you have a throttle only electric bike).
Whatever happens, you’ll always have a backup.
Lastly, a hub motor e-bike is way cheaper than a mid-drive one.
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Disadvantages of Ebike Hub Motor
As with all other things, hub motors have their issues.
First, a hub motor is more limiting than a mid-drive motor in terms of the e-bike’s wheel components like cassettes, tires, and rims. Since you’re stuck with the bike rim that came with a hub motor, fitting your preferred tire may not be an option. The hub motor’s width also often disqualifies cassettes with over seven speeds.
Second, hub electric motors are generally heavier compared to mid-drives. What’s worse? That extra weight isn’t sprung on suspension bikes, which transfers most of the bumps to you, the rider, and reduces the overall effectiveness of the bike’s suspension system.
That said, a hub motor’s heavy nature can also positively affect the bike’s balance. In several cases, it’ll be advantageous to have a motor’s weight further backwards or forward on one of your e-bike’s wheels.
That’s particularly true for e-bikes whose batteries are rear-mounted, since in these cases, front hub e-bike motors help redistribute the bike’s weight and evenly disperse it at the bike’s center section.
The third and most significant disadvantage with hub motors is that they only permit a single speed gear ratio. Even though this is generally alright for flatland riding, a high torque gear coupled with a lower speed would be better for hill climbs.
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Front Hub vs Rear hub ebike
Hub motors can be installed as a front or rear wheel motor.
When using an ebike conversion kit – the front wheel hub motor is easier to install and also cheaper than the rear hub motor. They are also easier to work with if you get a flat tire, and allow for any rear wheel gearing system desired.
Rear ebike hub motor kits take a little more installation effort but also get better performance for the rider and usually provide more consistent acceleration and get better traction. They do restrict the pedaling gears and in general derailleur gears are used.
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Advantages of Mid-Drive Motors
The sole reason Mid-Drive e-bikes were designed was to improve upon several shortcomings of hub motors.
For starters, mid-drive e-bikes allow riders to use a true torque sensor as the pedal-assist system. These sensors use the crank to measure how hard you’re pushing the pedals so they can regulate the motor’s power accordingly. Hub motors, on the other hand, often use cadence sensors for assistance. Cadence sensors only regulate a motor’s power based on pedal speed, which can cause awkward and jerky motor timing, particularly when you’re moving the bicycle around obstacles or riding up a hill.
Changing tires on mid-drive e-bikes is also way easier since you won’t need to deal with a heavy hub motor in the way. You just change out the tires like you would on regular pedal bikes. Better yet, this feature awards you the freedom to use any cassettes, tires, and wheels that you desire.
The single biggest advantage mid-drive e-bikes have is their speed gear ratio. Unlike hub motor e-bikes, mid-drive models allow riders to power their e-bike’s rear wheels through the same gear set and chain as the pedal drive system, implying that one can pick a lower gear and power up sharp hills or accelerate from a stopover with fantastic torque.
mid-drive e-bikes can also climb hills way longer than those with hub motors (which tend to overheat on lengthy steep climbs.)
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Disadvantages of Mid-Drive Motors
Of course, mid-motors have disadvantages as well.
The first downside of mid-motors is one that most people do not consider until they try to come to a stop. With mid-drive motors, you can only shift when the bike is in motion (except for bikes with rear internal gear hubs, and these are hard to come by.)
That implies that if you find yourself flying down a street but need to stop for some reason, you’ll need to remember to downshift before stopping. Otherwise, your bike will be stuck in top gear when it’s time to pull away, which will, in turn, hurt your acceleration.
Because of a mid-drive motor’s high number of moving parts, chances of failure also increase exceptionally. If the motor is directly built into the bicycle’s frame and it fails, replacing it can be more expensive than just swapping out a hub motor. What’s more – E-bikes with mid-motors are way more expensive than the mass-produced and tried & tested hub motors found in most e-bikes.
Perhaps the biggest flaw of mid-drives is that they can be unforgiving on an e-bike’s drive system. Healthy humans put out approx. 100 Watts of power during regular rides and up to 250 Watts during hard sprints. On the other hand, mid-drive motors put out between 250 and 750 watts of power constantly. That’s like letting professional cyclists hammer on your bike’s pedals throughout the day. A standard bicycle chain doesn’t stand any chances.
In fact, if you’ve spent time on e-bike forums, you know snapped chains are probably the number 1 issue reported by mid-drive e-bike owners.
Friction Drive E-Bikes
Any E-bikes explained guide would be incomplete without touching on friction drive e-bikes.
It’s undeniable that mid-drive and hub motors reign supreme today. That said, there is a lowly cousin of hub motors that was popular in the early days of modern e-bikes, i.e. friction drive e-bikes.
As their name implies, friction drive bikes work by powering the motor through a friction connection. This connection will usually manifest itself in a roller on the e-bike’s rear wheel. The rollers are then connected to the motor’s output shaft and are occasionally the motor’s shell itself.
Lastly, some sort of abrasive coating is applied to the roller to help it grip the tire, and a certain level of tension has been applied to keep the tire connected to the roller. Whenever the throttle is engaged, the roller turns the tires, which, in turn, propels the e-bike.
Are you wondering why these friction drive e-bikes lost out to hub and mid motors? Well, the friction drive system presented many problems. First, the fact the wheels are powered through rubbing not only results in a lot of energy loss but also causes tire wear because bits of rubber are constantly scrapped off.
Worse yet, the friction drive system wasn’t an all-weather option. Since the friction drive system only works with sufficient friction, a little water on the tire is enough to drop the friction coefficient considerably.
Mid-Drive vs Hub Motors: Final Thoughts
The short answer; it depends on your needs, requirements, and personal preferences.
The reason hub motor e-bikes have reigned for so long is, THEY WORK and are also generally cheaper than mid-drives. Front wheel hub motors are also low maintenance and great for everyday riders. Rear wheel hub motors do take some more maintenance but leave the front end more maneuverable. That said, Mid-drives also offer lots of improved features over the older hub-motor models. A lot of everyday bike riders and commuters prefer the unobtrusive, stealthy, and lightweight nature of mid-drive motors. Afterall a mid-drive is more like a standard bike.
It boils down to features that fit your situation best.