DIY e bicycle. DIY e bicycle

How to Transform Any Bike Into an E-Bike With One Click Using the Skarper Motor

You don’t have to invest in a dedicated e-bike to enjoy the benefits. Here’s how to use the Skarper motor on your existing bike.

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For those who are curious about e-bikes, conversion kits can open up a new world of riding. And while they’ve been around for years, most of them are difficult to install and leave your bicycle looking like a Frankenstein creation with control mechanisms bolted onto seat tubes and a tangle of zip-tied wires ruining a once pretty bike.

In the future, e-bike conversion kits may become so small and powerful that they’ll fit inside your bottom bracket and other riders will have no idea you’ve got a motor built into your bike. A British start-up called Skarper is already moving the needle in this direction.

How the Skarper E-Bike Motor Works

E-bike conversion kits are a great option for people who love to bike, and research in Transportation Research Interdisciplinary Perspectives found that those who rode e-bikes got more exercise minutes per week than those who rode normal bikes. The Skarper motor aims to give you the benefits of an e-bike with as little hassle as possible.

The Skarper e-bike motor differs from most motors you’d consider when building your own DIY e-bike in one major way: it powers your bike with a specially engineered disc brake rotor called DiskDrive instead of a replacement front or rear wheel with an integrated motor, a friction-drive system, or a mid-drive bolt-on.

Because of its design, Skarper can be fitted to any disc brake bikes with 160mm rotors, which is the most common rotor size on bikes equipped with disc brakes. Bikes with a 140mm rotor will work with the Skarper when using an inexpensive brake caliper adapter.

Skarper’s vision is for a rider to attach a motor to their mountain bike to climb and then detach it and stick it in their backpack to descend. While this may work well on tame road climbs, it may pose a challenge for mountain bikers who ride any sort of technical ups or anyone who doesn’t want to carry a 3-kilogram weight in their bag.

Skarper has also engineered its e-bike motor to be fully detachable, which further distinguishes it from every other e-bike conversion kit on the market. This means that you can install a Skarper rotor on more than one bike in your stable, and transfer the motor between bikes!

If you already own one or more bikes, you’ll be able to transform every one of your existing bikes into an e-bike using a single unit.

Features and Benefits of the Skarper Bike Motor

What makes e-bikes so popular is that they come equipped with a motor, battery, and control mechanisms seamlessly built into the bike. The problem is that many cyclists who already own a decent bike aren’t ready to invest in a brand-new one. Or they don’t want to transform what they currently ride into a mechanical abomination.

Fortunately, Skarper’s minimalist design can be attached to any disk brake bike—from high-end carbon gravel bikes to super-comfortable commuters—in a clean, wireless way that doesn’t compromise the ride. It can also be easily removed, returning the bike to its original configuration.

The best part is that, when the motor isn’t in use, your bike will look and ride as if nothing changed. Most people won’t notice the slightly different-looking rotor, and it will add minimal overall weight to your bike.

The Skarper motor weighs just 300 grams, while the unit containing the motor and battery weighs about 3 kilograms. The unit attaches to tabs that you fit onto your non-drive side chainstay.

Skarper Motor Battery and Range

E-bikes come in a variety of different classes, each with its own battery size, range, speed, and power. Skarper claims the range of their 202Wh battery to be up to 60 kilometers with a charge time of 2.5 hours. If you’re running low and need some extra juice in a pinch, Skarper claims a 30-minute charge will give 15-20km of range.

While there are other long-range e-bikes that can travel over 300 kilometers on a single charge, most people who use their bikes in urban settings only ride their bikes for a few kilometers each day, so the Skarper should work for most people, such as those who commute to work and are looking for a little extra help to avoid arriving in a sweaty shirt.

The unit comes with its own charger, and you can charge the battery while on or off the bike. However, one major downside of the Skarper is that the battery is fully integrated and cannot be replaced like it can on most purpose-built e-bikes meaning that if you require service, you won’t be able to visit your local bike shop, you’ll need to send the product back to the manufacturer.

Skarper Motor Power

There are some really fast e-bikes out there. Skarper is not one of them. That said, the modest 250W motor puts out 50Nm of torque and claims a top speed of 32 kilometers per hour (restricted to 25km/h in relevant countries).

To detect the level of assistance required, Skarper claims to have developed something they call DynamicClimb what they call a bespoke algorithm—that measures your output and the incline of the road. By measuring the amount of effort you put out, Skarper can adjust its output to match your speed and cadence.

Installing the Skarper Motor

Skarper claims that the disc brake rotor can be installed by an experienced mechanic at a local bike shop in 5 minutes, while the average DIY’er should be able to replace their rotor in 10-15 minutes. You’ll need to add an extra few minutes to attach a wireless sensor to the pedal crank so that the DynamicClimb algorithm will work, and a few minutes to attach the brackets to your chainstay where the motor and battery will attach.

Once installed, simply press the only button on the unit, wait for the status light to come on, and hit to road.

Is the Skarper E-Bike Conversion Kit for You?

The Skarper e-bike conversion kit is appealing because it allows you to transform your existing bike into an e-bike without compromising ride quality. There’s no need to replace any of the wheels or to install a battery and control mechanism to the frame, and you can remove it anytime, meaning you can ride your bike as normal, or store the e-motor somewhere safer than a public bike storage locker.

Alternatively, if you’re ready to commit to the world of e-bikes fully, there are plenty of options that come with bigger, replaceable batteries, more powerful motors, and from companies that have proven themselves in the marketplace.

Is it legal to build your own eMTB? All the most important information and legislation regarding DIY ebikes

Ebikes aren’t just difficult to get hold of at the moment but are also getting more expensive. As such, it’s not surprising that increasing numbers of people are considering the apparently genius idea of building their own ebike. But is it legal to build your own eMTB? What are the legal requirements and potential pitfalls? We clarify things here.

The demand for ebikes in 2020 has left the whole industry facing unforeseen challenges. In our article “Bike boom in a crisis” we’ve explained the advantages and disadvantages of this change. In the last few weeks, more questions and guides regarding DIY ebikes have been circulating on social media. But what are you actually allowed to do and what do you need to pay attention to if you want to convert or build your own ebike? A quick warning: to be able to describe everything accurately, it’s important to look at legal regulations as well as DIN standards and various guidelines in detail. This article will be informative and interesting, but a little complicated too.

“I built a Chinese EBIKE!!” That’s the headline that YouTuber Rob Hancill from Rob Rides EMTB uses for his video documenting how he built a cheap eMTB using Chinese parts. The video ignited furious discussion about what’s legal and what’s not. Through one of countless Chinese online sellers, Rob bought a frameset, matching headset, rear thru-axle as well as a BAFANG motor and battery, importing them all to Great Britain. Is that even allowed?

Ebike or pedelec, what are we talking about?

When we talk about an ebike, we mean the legal definition of a pedelec, which is classified as equivalent to a normal bicycle. As such, you don’t need a licence or insurance to ride one. The motor (with its nominal power limited to 250 W) supports the rider’s pedalling input up to a maximum speed of 25 km/h. Internationally, the term EPAC (Electrically Power Assisted Cycle) is also used. This is where it starts to get interesting. By adding a motor to a bike, it becomes a pedelec, for which different standards and rules apply. For example, the EU Machinery and EMC directives both apply to pedelecs. So, this article is about the kind of ebike you can buy at your bike shop, except one that you’ve built yourself. Illegal, chip-tuned ebikes won’t be discussed here.

By adding a motor to a bike, it becomes a pedelec, for which different standards and rules apply.

What does the german Zweirad-Industrie-Verband (ZIV) say about self-built ebikes?

We asked ZIV Managing Director, Ernst Brust, to give us some legal grounding. “Pedelecs that are built by private individuals for their own use and that are used on public roads also fall under the Machinery and EMC directives and have to be tested according to the DIN EN 15194-2017 standard. That also includes providing a CE mark for the pedelec.”

But what exactly does DIN EN 15194-2017 for ebikes encompass? What do you have to demonstrate when having a bike approved? Industry leaders including Zweiradmechaniker-Handwerk,, VSF., Zedler Institute and ZIV have produced a document (German only) outlining what you need to know about retrofitting E-drives. In it, they list what is required to meet the standard and which documents must be provided:

  • Risk analysis
  • Bill of materials and disposal instructions
  • Proof of operational stability of all safety-relevant parts
  • EMC testing (Electromagnetic Compatibility) for the whole vehicle
  • Proof of operational and electrical safety
  • Printed original manual in local language
  • Conformity assessment
  • Declaration of conformity
  • CE compliant nameplate

There are several possible legal consequences for retrofitting by a dealer or end-user:

  • Committing regulatory or criminal offences
  • Liability of the dealer for personal injury or damage to property
  • Loss of public liability insurance cover
  • Loss of licence to trade
  • Consequences under competition law

(German) Product Safety Act

The Product Safety Act ensures that every manufacturer guarantees the safety of their bikes during use, independent of any required standards. For eMTB manufacturers that means they have to exceed ISO 4210 and EN 15194. In doing so, the manufacturer has to orient themselves by the current scientific and technological development as meeting standards doesn’t automatically exempt them from liability claims.

Machinery Directive 2006/42/EC

Fundamentally, every pedelec that is sold in the EU has to have an EU conformity declaration. This is usually printed in the manual or provided as a separate document. Paragraph 2 (i) of this Directive clearly states, “[…] any natural or legal person who places on the market or puts into service machinery or partly completed machinery covered by this Directive shall be considered a manufacturer.” Put simply, that means that private individuals also have to stick to the Machinery Directive. If you meet its requirements, you are allowed to furnish the machine, in this case, the pedelec, with a CE mark. If you’re technically versed and want to read more about the topic, you can find out more about the Machinery Directive here.

Inside the EU, a pedelec built by an individual for private use also falls under the Machine and EMC directives and has to be tested according to DIN EN 15194-2017. That also applies to the transaction-free exchange of a self-built ebike, where gifting the bike counts as putting it on the market in the EU, with all the associated requirements. That includes a CE compliant nameplate on the pedelec. (Jens Müller)

EMC Directive 2014/30/EU

The 2014/30/EC Directive on Electromagnetic Compatibility (EMC) regulates almost all electric devices in the EU market. Manufacturers of equipment are obliged to prove via conformity assessment testing that the device meets requirements. In turn, they must produce technical documents, provide a manual of operation together with safety information and place the CE marking.

CE marking

CE marking is the responsibility of the manufacturer and only rarely is the product independently tested. In the first instance, this mark is a type of promise. It says that a product meets relevant EU standards and has been tested accordingly. Every bike that you buy online or in a shop must have a CE mark.

Conformity declaration

A conformity declaration is the manufacturer’s or importer’s way of demonstrating compliance of a product with EU directives and standards.

  • The data required in the declaration varies depending on the type of product.
  • Liability is usually assumed by the manufacturer.
  • If the manufacturer or importer fail to provide a conformity declaration for their product, they can be fined up to € 30,000.

International standards

Two standards, ISO 4210 and EN 15194 apply to ebikes. Pretty much all frames and bike parts worldwide are tested and approved according to these standards.

  • ISO 4210ISO 4210 for bicycles (applicable in Europe and internationally) describes standardised tests that define the testing protocols for the industry. However, ISO 4210 assumes a maximum system weight (bike rider luggage) of 100 kg.
  • EN 15194Alongside ISO 4210, EN 15194 additionally covers ebikes. EN 15194 applies to EPAC (Electric Power Assisted Cycles) which are equipped with pedals and an electric motor and that get used on public roads. EN 15194 also defines testing protocols, though with increased loads and a maximum system weight of 120 kg. However, this standard is based primarily on road and trekking bikes and is mainly intended to ensure that E-drives and components meet minimum requirements and work properly together.

What options are there for self-built ebikes?

For this article we considered the following three scenarios in more detail:

  • Converting a bicycle to an ebike with a retrofit kit.
  • Building an ebike up yourself with a frameset.
  • Building up an ebike from individual parts.

Converting an existing bicycle to an ebike with a retrofit kit.

If you can find a dealer who will convert your much-loved bicycle (for which ISO 4210 applies) to an ebike (for which EN 15194 will also apply) you’re off the hook because the dealer assumes liability for the conversion. Legally speaking, the dealer has created a new product and has to carry out all the certification mentioned above themselves. They’ll have to do that for every individual conversion they undertake. If they don’t then they take all risk on themselves and can be held fully liable. Even the best bike mechanic won’t be able to tell with absolute certainty whether a frame or components are suitable for a conversion. For older bikes, there are also factors like material fatigue and treatment of the bike that have to be considered. Any dealer countenances high risks doing this and should be aware of that fact.

We might have had many customer requests over the last few years but in the end, we decided not to offer conversions as legally, that would have turned us into manufacturers which has a whole string of consequences. (Marcus Heinz)

A further option is buying a conversion kit from your dealer or online and to do the work yourself. But here too you have to be aware that the person who converts their bike technically becomes the manufacturer of the machine. If you want to build a legal bike, then you’ll have to have your bike tested even as a private individual. Converted pedelecs all have to meet the requirements of Machinery Directive 2006/16/EC.

Tip: Check first whether upgrading your bicycle to an ebike is even worth it. For sporty eMTBs we have our doubts and buying a bike used is surely the more sensible option. You can find out everything you need to know in our buyer’s guide.

Building an ebike frameset up yourself

Significantly more elegant, but also more expensive, is the option of buying a frameset from a manufacturer like Specialized. Having decided on what you want, you’ll get a frame including a motor, battery and shock already fitted. Then you’ll just have to add wheels, brakes, fork, bars and other components to complete the build.

The S-Works Turbo Levo frameset can be purchased from Specialized for € 5,999. We talked with Dominik Geyer, Leader Global Turbo Business at Specialized, about what you have to consider when buying a Levo frameset to build your own ebike.

E-MOUNTAINBIKE: Do you receive an EC conformity declaration and a CE mark with the purchase of a frameset? Specialized: Yes. We sell the frameset as an “incomplete machine” with all required technical documentation and a declaration of incorporation. A CE mark isn’t required here.

E-MOUNTAINBIKE: Is a Specialized Owners Manual provided too? Specialized: Yes. This serves as a guide for our customer’s own documentation and as a reference for possible builds.

E-MOUNTAINBIKE: What does a customer have to be aware of when buying the remaining parts for their frameset? Specialized: The customer has to make sure that the components are compatible with the frameset and that they are suited to the intended use of the complete bike.

E-MOUNTAINBIKE: Having assembled CE-marked components, has the customer fulfilled the requirements of the Machinery Directive or do they have to do anything else? Specialized: The customer just has to make sure that the complete bike conforms to the clauses of the currently applicable directives and that the conformity assessment has been carried out according to them.

Tip: Individualising your own eMTB might be exciting, but for anyone who isn’t a handy mechanic or doesn’t have the right tools we recommend buying a complete bike, especially as any cost savings will be limited.

Building up an ebike from individual parts

Are you allowed to build up your own ebike? Yes, in principle you’re allowed to build anything you want. If you want to be able to ride on public roads legally with it then, as mentioned previously, you have to conform to the Machinery Directive even as a private individual. However, not sticking to the standards (see glossary) generally doesn’t lead to sanctions for private parties, an obvious grey area. What’s important is that you don’t exceed the 25 km/h assistance limit and that the bike doesn’t ride faster than 6 km/h using a throttle/push-assist without pedalling. Otherwise, the bike would count as a motor vehicle and be regulated under much stricter guidelines. When building a bike yourself you have to know which motor you want to use as it has to fit the frame. Unfortunately, you’ll quickly reach the limits of this venture when trying to buy the motor. The big players like Bosch, Shimano, Brose, Yamaha, FAZUA, Mahle and TQ don’t sell their motors directly to end-consumers.

The only option remaining is importing from Asia, like Rob Hancill from ROB RIDES EMTB ended up doing for his video. He ordered a BAFANG motor via an online dealer in China. In response to our question, Katherine Ma from the BAFANG marketing team in Shuzu, China made it clear that BAFANG doesn’t sell motors directly to end-customers. So, if you buy a motor in China, whichever source it may come from you will have to turn to the seller directly for guarantee and warranty claims when it comes to Bafang’s Warranty Policy.

Having obtained a motor, you have to be sure that the frame you buy also has the corresponding mount. In addition, the battery has to be compatible with the motor and the charger. The so-called system package has to be right. It should be obvious that building an ebike yourself requires quite a bit of knowledge and know-how. Not everyone will be technically capable of building their own eMTB and a particular concern is assembling everything so that it actually works and there aren’t safety-critical errors. Be aware: most ebikes covered in the media as going up in flames and causing damage were self-built bikes.

As such, it’s especially important to pay attention that every part you buy comes with a CE mark. Take care when importing things yourself, for example from China. If customs inspect your product and don’t find a CE mark, the product will be returned or destroyed at the cost of the customer.

Tip: Building an ebike yourself might be appealing for some but the significant obstacle of no big-brand manufacturers making their motors available directly to end-customers means we would advise against a self-build from individual parts.

What do testing and a CE mark cost?

So what do you need to do to be able to operate a pedelec legally on public roads? We asked Marco Brust, Managing Director of, a renowned testing institute in the cycling industry. According to him, the following must be met:

  • (German) Product Safety Act
  • Machinery Directive
  • EMC Directive
  • Low-voltage Directive

To test a complete bike (the complete vehicle and individual parts) the cost is around € 20,000 to € 25,000. EMC testing alone costs around € 3,000, meaning the idea of saving any money is immediately invalidated. So, if you’re searching for a cheap bike, you’d be better off looking at our budget group test than building an ebike yourself. Adding in the costs for a CE mark and testing the bike, affordable and legal eMTBs aren’t a realistic prospect.

Will personal liability insurance pay out in the event of damage or loss with a self-built ebike?

What legal consequences could there be in the event of damage or loss with a self-built ebike? We got in touch with the Director of Communication for Property Insurance for ALLIANZ Deutschland, Christian Weishuber, to clear up this question.

E-MOUNTAINBIKE: An individual builds their own ebike from available components (frame, motor, battery, wheels etc.) with motor assistance up to 25 km/h. According to the EU Machinery Directive, the individual is the manufacturer of the ebike and is responsible for the testing needed to obtain a CE mark. However, this CE mark is not present and this ebike causes damage or loss. Will this be covered by personal liability insurance? Christian Weishuber: A missing CE mark doesn’t automatically mean a loss in coverage for personal liability insurance. For the situation described it depends on the underlying policy, the circumstance of the damage (who is at fault), the claim and the condition of the eMTB. Our old policies don’t provide cover for the use of motor-powered vehicles (which also encompasses pedelecs up to 25 km/h). With new personal liability contracts, the use of powered vehicles that are not subject to compulsory insurance is covered. Here the damages caused by the use of a pedelec (up to 25 km/h) are insured too.

For fines or costs related to retrospective approval, insurance cover is not provided.

According to our correspondence with ALLIANZ, personal liability insurance will cover third-party liability for a self-built ebike even if it doesn’t conform to norms and standards like the conformity declaration, CE mark etc. In a followup call, they confirmed that personal liability insurance will cover third-party liability even due to gross negligence. Important: it’s crucial to check what cover insurance providers offer on an individual basis! A general enquiry isn’t usually enough. It’s best to have your current policy inspected as the terms can vary depending on when it was created/how old it is.

In contrast to dealers, end-customers are still in a grey area when it comes to liability. However, that doesn’t give you carte blanche. The circumstances of the damage (who is at fault), the claim and the condition of the ebike all play a role. That’s why insurance providers will investigate individual claims – so there is still a risk. Apart from that, with a self-built ebike, there are no guarantees regarding product liability in case something does happen.

Personal imports of ebike motors or conversion kits from Asia

We only want to touch on the topic of customs and duty briefly. Fundamentally, postal or courier deliveries from a non-EU state have to pay customs duty. We talked with Jürgen Wamser, Deputy Press Officer for the Department of Taxation in Bonn, about imports from China.

E-MOUNTAINBIKE: Do parts ordered from China (frame, battery and motor) have to have a CE mark when they are imported and does this also apply to personal imports? Jürgen Wamser: If a company from a third country (non-EU) sends a product to a private person in the EU as part of its business, this person is responsible for sticking to the European product safety regulations. During import, customs controls these shipments and if it believes that any regulations are being broken, will inform the relevant market regulators. Customs is not able to draw any conclusions about the legally stipulated product requirements. That’s what market regulators are responsible for.

E-MOUNTAINBIKE: What happens if the CE mark is missing or fake? Jürgen Wamser: If the market regulator decides that a product can’t be allowed to enter the market, generally the only consequence for personal imports is that the item is returned or destroyed.

E-MOUNTAINBIKE: Are you aware of any cases where bike parts imported from China were seized by customs due to a missing CE mark or other infractions? Jürgen Wamser: There are no statutory provisions for customs to seize products that don’t conform to product safety regulations. The item will either be returned or destroyed. Statistics on this are not collected.

If you want to get more detailed information about ordering products online from non-EU states, you can find out more on the customs website.


Is it worth building your own ebike? If you ride your self-built ebike without a CE mark you’re not conforming to current rules and regulation. In contrast to dealers, the consequences for private individuals sit in a legal grey area and private liability insurance will often cover you – depending on your individual policy. In terms of the ebike, you won’t have access to the big brands when it comes to selecting a motor and building a perfectly tuned, trail-worthy ebike would require a lot of technical know-how. So, if you don’t want to tinker but want to ride, leave building eMTBs to the pros. If you dare to build an ebike yourself nonetheless, be warned: the supposed cost savings might quickly become a buzzkill!

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Words: Manne Schmitt, Susanne Feddersen Photos: Rob Hancill, E-MOUNTAINBIKE Magazine, diverse

Simple E-Bike Circuit [Electric Bike]

This E-bike or electric bike circuit explained below can be used as the control circuit for constructing a homemade E-bike, with the help of a permanent magnet motor DC (PMDC motor), and a Li-Ion battery.

An electric bike is basically a bicycle powered through a motor and a battery, which does not require a manual pedaling for operating the bicycle. In some bikes a manual pedal assistance is also provided.

In this post we won’t be discussing the entire wheel mechanism of the E-bike, rather we will only learn how to build the control circuit for the motor, and a finger press accelerator mechanism.

The whole idea is designed by me, with perfect understanding and brain simulation. However, the final design will need to be tested practically to confirm the proper working of the E bike circuit.

The idea is actually quite unconventional since this E-bike is supposed to operate without any pedal assistance. Instead the bike will depend entirely on the battery power. The battery could be charged externally through a suitable battery charger unit and grid power.

Basic Working

The E-bike project basically includes two elements, A PWM motor controller circuit and a finger press operated throttle or accelerator circuit. information regarding the basic working details of the system is given below:

  • A PWM motor controller circuit which responds to an external signal and proportionately varies the speed of the motor through a correspondingly varying PWM output.
  • A finger press accelerator unit, consists of an LED and an LDR, arranged one beside the other. The light from the LED is directed on a shaft and is reflected back towards the LED. The amount of light reflected from the shaft is determined by the proximity of the shaft towards the LED/LDR module, which is in turn determined by how much the shaft is depressed towards the LED/LDR arrangement.
  • The pressing of the shaft is implemented by pushing a attached push button, by the rider.
  • As the button is pressed deeper, the attached shaft moves closer to the LED/LDR module causing an increased amount of light to get reflected on the LED.
  • As the light on the LDR increases, the LDR resistance decreases, and this information is converted into a signal which causes the PWM width from the PWM controller to increase.
  • The increase in the PWM width causes the E-bike motor speed and torque to increase, which in turn causes the speed of the E-bike accelerate.
  • When the pressing of the accelerator button is slowly released, the opposite response is achieved, which causes the PWM width to decrease and a subsequent reduction in the acceleration of the E-bike speed.

Finger Press Accelerator (Throttle)

The function of the finger press accelerator is to provide the rider a facility through which he or she can increase or decrease the speed of the E-Bike motor through a corresponding pushing or releasing of the accelerator push button.

As explained above, the working of the finger pressed accelerator unit can be understood through the following points, and by referring to the following two diagrams.

As can be seen the above diagrams, the finger push accelerator for the E-Bike consists of a spring loaded shaft, which is mechanically attached to a push button.

We can also see an LED/LDR arrangement fixed parallel to the spring loaded shaft, such that the light from LED can fall on the inner surface of the shaft and get reflected towards the LED. The amount of light that can be reflected depends upon the proximity of the shaft toward the LED/LDR configuration.

Due to the spring tension, the shaft pushes the button outwards. When the push button is pressed with finger, it pushes the shaft inwards causing it move closer towards the LED/LDR module.

As the shaft is pushed harder, the shaft moves closer to the LED/LDR assembly causing proportionately greater amount of light to be reflected from the LED to the LDR.

This causes the LDR resistance to decrease. Now, if the pressure on the push button is loosened, the shaft moves away from the LED/LDR assembly causing a proportionately lower amount of light to be reflected towards the LDR. The LDR resistance now increases.

The above increase and decrease in the LDR resistance value is sent to a PWM controller circuit.


Here, the varying LDR resistance is appropriately converted to a signal which causes the PWM circuit to generate a correspondingly varying PWM signal output.

PWM Controller Circuit

The function of the PWM controller circuit is to sense the varying resistance of the LDR and convert it into a correspondingly changing PWM output. The PWM output is then fed to the E-bike motor for achieving the required speed control.

The circuit is built around a couple of IC 555, as shown in the following figure.

The working of the motor PWM controller circuit can be understood with the following points.

IC1 is configured as a simple 555 astable multivibrator circuit which generates a 80 Hz rectangle wave output at its pin#3.

This 80 Hz frequency is sent to pin#2 of IC2 which is another IC 555 configured as a PWM generator.

The 80 Hz frequency is first converted to 80 Hz triangle wave with the help of an RC integrator built around R4/C3 via T1.

This triangle wave is fed to pin#6 and pin#7 of IC2, which is subsequently compared with the voltage at pin#5 of IC2 to generate the corresponding PWMs at pin#3.

Thus, depending upon the potential level at pin#5, the output pulse at pin#3 of IC2 can vary from thinner to wider PWMs and vice versa.

The potential at pin#5 of IC2 is determined by the emitter voltage of T2.

T2 being configured like an emitter follower, produces an emitter voltage which is perfectly equivalent and in sync with its base voltage.

The base voltage of T2 is determined by the resistance of the LDR, which is in turn determined by the reflected illumination from the adjacent LED lamp.

How the light from the LED is reflected on the LDR is already explained earlier, under the finger press accelerator paragraphs.

Therefore, as explained before, when the shaft inside the finger press accelerator unit is pushed closer to the LED/LDR assembly, the light on the LDR decreases, causing higher amount of potential difference to be generated at the base of T2.

T2 being configured as an emitter follower, causes this rising potential to be sent to the pin#5 of the IC2.


IC2 now translates the same into an increasing PWM at its pin#3.

Exactly the opposite happens, that is reduction in the PWM happens when the accelerator shaft is slowly released, due to a decreasing illumination on the LDR.

How to Implement the E-Bike Circuit

Implementing the proposed electric bike circuit is just about hooking up the PWM controlled motor with the rear wheels of a bicycle.

The bicycle may have a pedal assist, however unlike conventional E-bikes, here the pedaling is not used for initiating the PWM circuit.

The PWM motor controller can be initiated simply by pressing the accelerator button.

However, if the bicycle is not first initiated through manual pedaling could cause a lot of strain on the motor and the battery, and the motor may be unable to push the bike forward.


Therefore, it is necessary to generate some initial kinetic energy on the bike through pedaling and only then push the accelerator switch, so that the motor can further assist the rider, allowing the pedaling to get easier.

Motor Specifications

The suggested motor for the above E-bike project is a 24V 250 watt permanent magnet DC motor (PMDC), as shown below:

An attached gear box is not required for the proposed application, since the circuit is PWM based, and the initialization of the motor will be soft and slow, rather than quick and abrupt.

Using Force Resistor for Throttle Controller

For the finger press accelerator unit, if you find the LED/LDR assembly mechanics a little cumbersome, you can easily replace it with a force sensing resistor for getting the same results with higher efficiency, and in a more compact way. The modified design can be witnessed in the following diagram.

When pressure is applied on the force sensing resistor through finger pressing, the resistance of the force sensing resistor drops quite linearly, which is translated into PWMs with increasing width. The motor thus gains speed and acceleration.

When the finger is released, the pressure is withdrawn from the force sensing resistor, causing the PWMs to get narrower. The speed and acceleration of the E-bike motor now deceases proportionately.

Since the force sensing resistor can be quite sensitive to pressure changes, it is recommended to use a thick rubber pad over the resistor, to blunt of the response a bit.

Battery Specifications

The battery recommended for the above E-bike circuit is a 24V 10 Ah Li-ion Battery. A 15 Ah rated battery can be even better than a 10 Ah battery. The example of the battery can be seen in the following image.

The voltage of the battery will need to be monitored through a low battery indicator circuit, or through a digital voltmeter or both.

Once the battery voltage reaches below 22. it must be removed from the E-bike and charged at home through an appropriately rated Li-Ion charger.

This concludes the construction details of our simple E-bike controller circuit.

If you have any specific questions related to the subject, please fee free to post them through Комментарии и мнения владельцев below, I’ll most happy to answer them.

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The Ultimate Starter Guide to DIY Ebike

Electric bikes gradually replaces traditional and regular bikes. They are not only efficient but also premium with sleek designs. Since it’s becoming a trend in society, an individual needs to understand the concept of DIY Ebike. Sometimes, users decide to update their existing traditional Ebike into the electrical mode. However, a user needs the best e-bike conversion kit to achieve this purpose. A user also needs to choose the right bike. It will be unrealistic to pick any random motorcycle in your garage with the hope of achieving a premium electric bike. The bike shop in your residence should be able to recommend the best option for you.

The fundamental concept of the DIY Ebike is to curb the high rate of electric bicycles. Users can beat the traffic at a lesser cost using a DIY e-bike kit. This article contains information about electric bike conversion kits and other related exciting topics for the readers.

Choosing the Best Battery for Your DIY Ebike

An electric bike’s battery is one of the critical features you need to develop a DIY e-bike. Electric bikes operate on electrical energy against the traditional means of commuting with fossil fuel. Hence, the battery serves as an energy reservoir for this transport mode. Meanwhile, a battery determines the rider’s maximum speed, voltage, and riding capacity.

Your battery capacity describes how far you can travel before it runs out. If your battery capacity is high, a rider can cover a longer distance and vice versa. However, some factors may influence the distance level, such as weather conditions, support, and body size. Most electric bikes with high battery capacity are usually more expensive than those with low battery capacity. Nevertheless, Haidong has several battery capacity ranges that suit many users’ preferences.

An electric bike with a high voltage rate also yields massive motor operation and power. Several users request different voltages, depending on the ride’s intended purpose. For instance, the required voltage for rough terrain will vary from a south road. Meanwhile, experts and experienced riders opt for high voltage e-bikes for driving on rough terrains. Other factors to consider in choosing a suitable battery for a DIY e-bike are highlighted below.

Understanding the basic battery parameters, bearing in mind your requirements, financial capacity, and taste.

Communicate effectively with your battery provider and in more explicit terms for every product or kit agreement.

Ask yourself the maximum weight of the electric bike.


Installing Motor in your Bike System

There are popular motor types in electric bikes: the rear hub, front hub, and mid-drive motor. It would help if you altered the front wheel of an e-bike to use the front motor. Users with rear hub motors put the motor in the middle, alternating the rear wheel position. Also, a mid-drive motor has the pedal assist function, with the motor located at the bottom of it. Each of these motors serves a distinct function. They all have pros and cons, while a user is in the best position to make a choice or preference.

The mid-drive motor is often popular among DIY e-bike enthusiasts. They are user-friendly because they allow riders to adjust their speed and torque appropriately. It is also the best option for a rider who wants to go uphill. Meanwhile, hub motors are cheaper than mid-drive motors. An average engineer can try the hun motor drive, especially riding downhills.

Assembling your Electric Bike Kits

Assembling electric bike kits has its challenges, except you have studied the engineering input. Hence, it will become easy at this point. The start phase will require you to put the inner tube and tire at the rear wheel. These components are usually removed from the hub motor wheel. Slowly screw them to the electric bike motor to prevent the elements from threading. If you have trouble aligning your motor unit to the disc brake, adjust them properly before continuing. This is a DIY e-bike strategy you should be cautious of.

If your kit already marked the torque arms as the left and right positions, fix them into the axle nuts. It may take about ten minutes, then set the controller upright. If the pedal is immediately above the down tube, it may not be easy to notice it. After successfully fixing the controller, return the electric bike to its previous position. Afterwards, place the e-bike upright and let the tires support its weight. Then, go ahead to include the e-bike battery.

Implement basic engineering skills while fixing the battery, especially if the mounting plate holes do not align with the bottle bolts. Hence, draw small holes in this frame region, where the screws can fit perfectly. The best solution is to replace the shock so that the battery can fit in. Hence, this will not require a shock replacement. In most cases, a 21’’ frame is compatible and ideal for most electric bike systems.

The next assembling tool for your DIY e-bike is the cycle analyst meter. Make sure the handlebars can accommodate the cycle analyst meter. Also, the throttle assembly should fit into the right handlebar appropriately. The bottom bracket will bear the pedal-assist function, considering it’s a DIY e-bike. Wherein pedal-assist is also based on users’ choice. After setting these, assemble all the cable wires. Connect the cables to the controller, following each unique size and location. You can try cable wires for a neatly done connection.

The Step-by-Step Procedures

Beyond batteries and motors, other features contribute to the conversion success rate. Any slight fault from these features is powerful enough to affect the overall performance. The best bikes are categorized by their features, performance, and effectiveness. An e-bike conversion kit often has an installation manual. However, this guide provides the step-to-step process of installing your electric bike kit.

Step One

Many users make a mistake by starting the bike without prior testing. You want to make sure the needed materials are complete. Even though having a complete package will attract an extra fee, it is the best caution step.

Step Two

The best step is to install your motor unto the machine. However, the installation procedure will be determined by the rider’s type of motor. Also, check that the brake is in good shape and fix the speed controller and accessories to the e-bike frame.

Step Three

The three key features at this stage are the throttle, battery, and speed controller. When these three are appropriately connected, your e-bike will operate without interruption. Also, make sure to use the proper cables to prevent any fire outbreak or spark.

Step Four

The handlebar region is the spot for an electric bike display. This is where you see activities with the e-bike, such as the speed. Unscrew the display region, and tighten it back.

Step Five

A throttle should be connected to the brake lever. However, some DIY e-bike enthusiasts only fix the throttle to the brake level already. The ignition button will prove if you have done an excellent job or not. When an individual uses the switch button, the battery will be ignited, and the cycle analyst meter will light up. However, ensure the battery is fully charged before riding your bike into the cities.

Top Challenges while Assembling E-bike Kits

One of the main challenges people have is removing the shifter. Meanwhile, this can be quickly done when you have removed the handlebar. This can be time-consuming, so you need to use premium tools only. Also, make sure every other thing is in order before fixing the handlebar. A pretty tricky handlebars grip can be removed with water instead of oily spray. This will stop the substance from messing up the whole process.

Another challenge is installing the bottom bracket shell with the whole system, even though the diameter is compatible with the system. New bikes often have little pieces of metal at the bottom bracket. The solution is to identify if they are any metal stuck in the shell. When the bottom bracket area is free of anything that could stand in the way, you shall overcome these challenges.


If you have been thinking of investing in transportation, maximize the advantages of DIY e-bikes. Both cyclists and random riders are saved from the high of electric bike features. This is most especially common for mountain bikes. You can still enjoy the benefits of electric bikes without losing the attachment to your regular bike. Also, many young people find it attractive to convert their pedal bikes to electric bikes. This mainly applies when they live in a dense urban area.

Once you have the basic technical and electrical skills, you can easily add conversion kits to your bike. Ensure the electric bike conversion kit has everything you may need, and follow the instructions stated above in this article. However, make sure to run your DIY ebike in a less congested area before going into the cities. You can quickly identify any error or fault in the installation process and fix it up.

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