From the first electric bike with your own hands - to a promising startup. Staff stories REG.RU
REG.RU Technical Director Valery Studennikov tried to solve the transport problem for himself, and then turned his hobby into an interesting startup.
We present to your attention the story of the founder of Electron Bikes about how to make a powerful electric bike with your own hands, why speed lovers are not satisfied with the existing models of bikes and to what speed a normal-looking bicycle can accelerate.
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The first acquaintance with electric bikes
I first saw electric bicycles four years ago, in 2011, at a bicycle show in Moscow. Dear, inconspicuous, very weak in characteristics, but somehow they hooked, there was a desire to join this interesting mode of transport. A study of the market at that time showed that it was simply unrealistic to buy a ready-made electric bike with good performance at an adequate price. There are either very low-power and low-speed bicycles with a small battery on the market (China is weak in all respects or expensive, glamorous but still slow-moving Europe), or super-expensive monsters whose manufacturer’s value starts at $ 10,000 (Stealth Electric Bikes, Hi-Power Cycles), which also have their drawbacks (inadequately heavy weight due to the heavy frame and heavy motor-wheels, weak traction "on the bottoms" due to the use of gearless motors, a small power reserve).
But the insistent desire to get a noiseless, light and at the same time powerful and frisky electric bike has not disappeared anywhere. Therefore, we had to choose the only available option - to assemble the bike from the components available on the market, as many other enthusiasts do .
First pancake
The first “lump” was an attempt to assemble a bike based on a kilowatt MagicPie motor-wheel with a built-in controller, purchased in conjunction with a 10 Ah battery for installation on the trunk. It was possible to assemble the vehicle, but the joy of a new bicycle, which accelerated to an unprecedented 42 km / h, was short-lived — the trunk lived under the weight of the battery for exactly three days, breaking on broken Samara roads. Manageability and weight distribution with such an arrangement of the battery is also not very pleased. It was also hard for the rear wheel, which already gained weight - at the speed in the next pit it was easy to break through the camera or even bend the rear rim.
Therefore, during the next revision, the battery with the help of improvised mounts migrated to the bottom tube of the bike. As a result, the weight distribution turned out better, but the design looked scary and indecent. For the description of such creations of crazy hands, the domestic bike builders even got an established term - “shahid design” .
It was already quite comfortable to ride a bike with more proper weight distribution, but it became clear that a standard 500 W * h battery (50 V, 10 A * h) for a above-average power bike is not enough for a short time - you can get electricity from point A to point B, and back already only on the pedals. As a result, a large 1000 W * h battery (50 V, 20 A * h) was bought, which seemed to fit into the front triangle of the frame, but it had to be fixed with electrical tape;) It looked like this:
The resulting monster did not even spin the pedals due to the width of the battery.
It is clear that it was impossible to leave it that way.
It was necessary to come up with something with a battery - to change its spatial layout, so that the pedals would not be touched for it, and to deal with its mounting, making a reliable battery box. To accomplish this task, after a long search and screening of candidates, Alexander Kostyuk was recruited - an acquaintance from the cycling club "Velo Samara", who also deeply imbued with the idea of ​​designing an electric bike. Having many years of experience in constructing and building various prototypes of everything that just moves, he took on the task of constructing boxing. It was decided to make it from AMg sheet (aluminum alloy with magnesium) 2.5 mm thick, connecting with aluminum corners. Coloring boxing - powder. Also on the bike was installed power meter Cycle Analyst, which allows to measure a bunch of indicators, including power consumption in watt-hours per kilometer. With such a device one could no longer worry that the battery would suddenly discharge at the most inappropriate moment - every ampere-hour or watt-hour spent on the account. The result was this bike:
On such a device with a capacious, conveniently and securely fixed battery, it was already possible to safely ride around the city without the fear that something would fall off at the most inopportune moment. Yes, and the bike looked decently. The bike was ready exactly for the winter of 2012-2013 and showed itself perfectly in winter conditions, including driving in snowfalls, and in a blizzard and cold weather minus 35 degrees.
Only forward!
After the successful completion of the construction of the first apparatus, the idea arose to continue to design electric jigs with Sasha. I had a certain vision of what I wanted, and Sasha had a huge design experience.
We decided not to stop at what has been achieved because the Russian market at that time simply did not have electric bicycles (and now it isn’t) that we ourselves would like to ride. The niche of quite powerful (comparable in speed and dynamics with a scooter or motorcycle) and at the same time light and adequate at the price of electric bikes was completely empty. And low-power bikes were not at all interesting for Sasha and me, because we, active and young, wanted to ride “with a breeze”, so that the bike would have decent mileage and reliable construction for driving on the harsh Russian roads and off-road.
It was decided to create a universal electric kit, which allows turning any modern mountain bike into an electric one. Mountain bikes were chosen as a base not by chance - they are very popular in Russia (they make up the main class of bicycles for adults quantitatively), are universal (they allow you to drive around the city and off-road) and are reliable. It is also important that the parts and assemblies of mountain bikes are standardized, which also makes it possible to standardize the electric kit.
It was necessary to pick up adequate components for the bike and solve a number of engineering tasks:
- To pick up a motor capable of delivering more power and torque, while being light.
- Assemble a compact and lightweight battery of sufficient capacity, capable of holding large currents.
- Strengthen the rear wheel dropouts so that the high-torque motor axis does not turn in them.
- Develop response sensors for hydraulic brakes (serial hydraulic brakes with sensors are only beginning to appear on the market and have their drawbacks), because the automatic shutdown of the engine when the brakes are pressed is one of the basic standard requirements for electric jets. And mechanical brakes are no longer suitable for safe braking at the speeds that we intended to achieve.
- Think of solutions for powering the headlamp and rear light (with a signal) from the onboard voltage of an electric bike, with the built-in DC converter.
- Determine the appropriate connectors (preferably sealed), cycle computers-wattmeters, lighting and many others.
But the most important thing was that it was necessary to develop a universal box for the battery and controller for the rapid transformation of an ordinary serial bike into an electric one. The metal box previously assembled for this role was not suitable, since it required too much labor to be made and was sharpened in shape and size only for a specific frame.
The final solution was to be easy to install, easy to manufacture and cheap to produce.
Here is one of the first stages on this journey, boxing built in spring 2013:
Here is another one of the intermediate steps:
What happened?
As a result, years of work and experiments have developed truly versatile and much more aesthetic boxes, electrical kits and bicycles based on them:
The characteristics of these devices:
- speed - up to 63 km / h;
- power - up to 2.5 kW;
- battery capacity - up to 1 kWh;
- the range is 40 km at maximum speed (63 km / h) and up to 100 km in economy mode (30 km / h).
Here is a video of the movement of a powerful electric bike in the “urban jungle”:
In a rough terrain, the bike also does not fold:
More videos
Bicycle or motorcycle?
The bikes on the basis of the created electrical set turned out really very frisky, able to fully move in the city traffic at a speed of 60 km / h. According to the new rules governing the power and speed of electric jets, they formally do not belong to bicycles (whose electric power is limited to 250 W and 25 km / h), or even to mopeds (whose design speed should not exceed 50 km / h), and belong to the class of motorcycles. Moreover, the appearance of this bike does not cause any special suspicions - a seemingly ordinary bicycle with a box inside the frame. And the weight of the device did not increase much, the powerful electric kit adds only 14 kg to the bike, as a result, the weight of the finished bike is obtained in the region of 26 kg. Such a device for an adult man is fully capable of lifting the stairs, carried through obstacles.
So it turned out functionally quite a moped, but in a bicycle shell. As a result, you can take advantage of both types of transport: we have a “green light” everywhere (pedestrian areas, sidewalks, land and underground crossings, transition ramps, parks, paths and just off-road), while the speed and dynamics of a moped are available on the road / scooter (with more maneuverability than any scooter or motorcycle), which makes a powerful electric bike in real traffic conditions the fastest land transport in the city.
And although the power of our standard electric kits is already comparable to a moped, as a sports interest and experiment (not very cheap, as it turned out after calculating the cost of all components), heavy and powerful electric bikes were assembled based on Qulbix specialized spatial frames:
and Ukrainian "frame Chobotar":
These 6-10-kilowatt monsters can reach speeds of up to 90 km / h, while having the dynamics of a light motorcycle. And when you open a full gas from the place they get up "on the goat." A 3 kWh battery allows you to drive 120 km at a speed of 40 km / h or 40 km at a speed of 90 km / h, so you can use this bike as a long-distance suburban vehicle and for driving on the highway.
What's next?
The design of electric kits and electric bicycles Electron Bikes continues to improve constantly. Soon two models of the bicycle will be ready for industrial serial production:
“Standard” (based on the usual bicycle frame): power 2.2 kW, battery capacity 1 kWh, speed up to 63 km / h;
Electrochoppers (without pedals) “Electro-classic”: power 6 kW, speed up to 85 km / h, capacity of two removable batteries up to 3 kW * h;
and "Electro-Bober".
.The latter is also equipped with a unique parallelogram titanium fork, released in limited edition.
A little about the device electric bikes
At the end, a little about the device and components of electric bicycles, as well as technical difficulties that stand in the way of the creators of a powerful bike.
The main electrical components of the electric bike
The “heart” or muscles of an electric bike is an electric motor (more details about motors and their types below). Modern electric bikes use brushless DC synchronous motors (Brushless Direct Current Motor or BLDC), which allow them to work efficiently in a wide rpm range with high torque. Occasionally, asynchronous motors are used as central ones. (About “Shkondin's Engines”, about which there is so much noise on the Internet, you can release a separate exposing material;).
The “brain” of the electric bait is the controller . The controller controls the electric motor, applying at the right time the power to its windings, depending on the desired speed of rotation and power. The controller also controls the entire “logic” of the bike: at the entrance, receiving signals from the throttle position, mode switches (for example, in different modes you can limit speed, power or even turn back), cruise control buttons (it helps a lot when driving in the country mode), signals from the brake sensors (because you need to turn off the power of the motor when you press the brake lever or even include regenerative engine braking, if supported), etc.
The electric battery for energy supply of the heart and brain is stored in the battery . The normal voltage of electric bikes batteries is from 36 V to 48 V. High-speed devices can be equipped with high-voltage batteries (up to 100 V).
Currently, the vast majority of electric bicycles use lithium batteries (more on their types below), which have the best energy consumption. Heavy lead batteries are used only on the cheapest devices.
The battery consists of individual battery cells connected in series / in parallel.
The battery also has its own “brain” - this is the Battery Management System ( BMS ). It protects the battery from overcharging, overdischarge, exceeding the permissible current, and also balances the individual cells of the battery so that they are discharged evenly.
To display all the necessary information and accurate “calorie counting”, a power meter is needed, which allows you to say exactly how much energy is spent and how much is left. A specialized wattmeter combines the functions of a cycle computer, also counting speed, distance, and derived indicators, such as power consumption per kilometer of track (WH / km).
To power low-voltage consumers (headlamp, rear light, beep, repeaters), it is necessary to reduce the on-board voltage to a lower (5, 8 or 12 volts). For this, high-efficiency DC-DC converters are used.
The “brain” of the electric bait is the controller . The controller controls the electric motor, applying at the right time the power to its windings, depending on the desired speed of rotation and power. The controller also controls the entire “logic” of the bike: at the entrance, receiving signals from the throttle position, mode switches (for example, in different modes you can limit speed, power or even turn back), cruise control buttons (it helps a lot when driving in the country mode), signals from the brake sensors (because you need to turn off the power of the motor when you press the brake lever or even include regenerative engine braking, if supported), etc.
The electric battery for energy supply of the heart and brain is stored in the battery . The normal voltage of electric bikes batteries is from 36 V to 48 V. High-speed devices can be equipped with high-voltage batteries (up to 100 V).
Currently, the vast majority of electric bicycles use lithium batteries (more on their types below), which have the best energy consumption. Heavy lead batteries are used only on the cheapest devices.
The battery consists of individual battery cells connected in series / in parallel.
The battery also has its own “brain” - this is the Battery Management System ( BMS ). It protects the battery from overcharging, overdischarge, exceeding the permissible current, and also balances the individual cells of the battery so that they are discharged evenly.
To display all the necessary information and accurate “calorie counting”, a power meter is needed, which allows you to say exactly how much energy is spent and how much is left. A specialized wattmeter combines the functions of a cycle computer, also counting speed, distance, and derived indicators, such as power consumption per kilometer of track (WH / km).
To power low-voltage consumers (headlamp, rear light, beep, repeaters), it is necessary to reduce the on-board voltage to a lower (5, 8 or 12 volts). For this, high-efficiency DC-DC converters are used.
Difficulties of transition age
The task of creating a powerful bike is complicated by the fact that the entire component industry for electric bikes is currently designed for low-power vehicles. The class of powerful and high-speed electrobikes that stand halfway to motorcycles is only being formed, so the creators of such devices have to invent something at every step.
Batteries
Commercially produced batteries for electric bikes are created, as a rule, from elements that can not withstand high currents. The C-rating (the ratio of the current that the battery is capable of delivering to the battery capacity, expressed in ampere hours) of standard batteries, usually made up of lithium-ion cells, is no more than 1, while under powerful bicycles that we create, requires batteries with a C-rating of at least 2.5. That is, for example, with a capacity of 20 A * h, capable of delivering a current of 50 A for a long time, which, with a 50-volt battery, would allow a power output of 2.5 kW - the minimum of interest. As a result, the batteries have to be soldered (and now already to be welded using spot welding) independently from suitable elements. Search and selection of suitable elements by their characteristics, their testing and rejection is also a separate task. Now we use prismatic elements LiFePO4 and LiNiCo, which allow to create energy-intensive and compact batteries.
The main types of lithium battery cells
- LiFePO4 (lithium iron phosphate). They can be used in freezing temperatures up to -30 degrees, a fast charge is available in 45 minutes, they have the largest number of charge-discharge cycles (1500-2000), they allow to give more power, they are fire safe, not combustible. However, they have a twice lower specific capacity than lithium-ion batteries (i.e., 2 times higher weight with the same capacity), relatively expensive (but the unit price of operation is the lowest due to the large number of cycles).
- They are used as the main solution in sets for hardtail bicycles, however, due to their size, they are not suitable for installation in the front triangle of the frame of two-weight bikes, where there is very little free space.
- Li-Ion (lithium ion). Classic lithium batteries used mainly to power electronics. They are the lightest and most capacious, the cheapest, having the maximum specific capacity today (W * h / kg). However, they have a narrow temperature range of operation (from 0 to +40 degrees Celsius), a small number of charge-discharge cycles (300-400), do not allow to give large currents. These batteries are most often used in low-power e-bikes, but they are of little use for powerful devices due to their low C-rating.
- LiPo (lithium polymer). High energy intensity, almost the same as that of the elements of Li-Ion. Allow high bit currents, high C-rating. However, like Li-Ion, there are fewer charge-discharge cycles (300-700) and a narrow temperature range: when operating below 0, they fail, and in heat, short-circuits or mechanical damage can ignite. Because of its high fire risk, electric bikes are used only by fearless enthusiasts.
- LiNiCo / LiNiCoMnO2 (lithium-nickel-cobalt). Having the advantages of LiPo (high energy intensity and the ability to produce large currents), they lack their disadvantages: they have a wider temperature range, and, most importantly, are fire safe. As a result of its compactness, we are used in electrical kits intended for installation on two-suspension bicycles.
Motors
But the biggest problem in the task of creating a powerful and lightweight electric bicycle is represented by motors.
Serial motors are either too thin, or heavy, or have low efficiency, or overheat, or all at once;)
The motors used for electric bicycles can be divided into three classes, each of which has its drawbacks with respect to powerful electric washers.
Gearless motor wheels (direct-drive)
The force of the magnetic field is transmitted directly to the wheel, and therefore are called direct drive (direct drive).
Unpretentious, reliable, as they have no wearing parts, except bearings. Allowed to be used as an electric brake for regenerative braking. But they have two big drawbacks.
The first is a lot of weight. For example, a motor rated for 2.5 kW will weigh an average of 7 kg, and a motor for 6 kW as much as 12 kg. This greatly affects the weight of the finished bike. In addition, placing a heavy motor in the rear wheel shifts the center of gravity back (it becomes inconvenient to carry a bicycle, perform tricks / jump on it), and also increases the “unsprung weight” of the wheel, which, for the worse, affects its vitality, increasing the requirements for rim strength , the thickness of the spokes. In this regard, the wheels with heavy direct drives often need a motorcycle rim, because pick up the bike rim of the desired strength is difficult.
The second disadvantage is low efficiency when driving at low revs. For example, when driving uphill, through mud, sand, or off-road, where it is impossible to accelerate, such a motor will overheat. For example, when driving uphill 20%, a spherical direct drive motor on 6 kW will work at about 20% of its efficiency, and 80% will go to heat. In this mode, a powerful motor-wheel can overheat and burn in a couple of minutes, if it is not turned off in time (they usually implement an automatic shutdown of the motor based on a signal from a thermal sensor). This is not surprising: with a weak heat sink in the closed space of the motor and in low-efficiency mode, the windings heat up at the speed of a powerful electric kettle (4.8 kW to heat in our example with a 6 kW motor). However, so that the “kettle” heats up more slowly, you can “pour water” into it - some enthusiasts solve the problem with the help of water cooling .
The force of the magnetic field is transmitted directly to the wheel, and therefore are called direct drive (direct drive).
Unpretentious, reliable, as they have no wearing parts, except bearings. Allowed to be used as an electric brake for regenerative braking. But they have two big drawbacks.
The first is a lot of weight. For example, a motor rated for 2.5 kW will weigh an average of 7 kg, and a motor for 6 kW as much as 12 kg. This greatly affects the weight of the finished bike. In addition, placing a heavy motor in the rear wheel shifts the center of gravity back (it becomes inconvenient to carry a bicycle, perform tricks / jump on it), and also increases the “unsprung weight” of the wheel, which, for the worse, affects its vitality, increasing the requirements for rim strength , the thickness of the spokes. In this regard, the wheels with heavy direct drives often need a motorcycle rim, because pick up the bike rim of the desired strength is difficult.
The second disadvantage is low efficiency when driving at low revs. For example, when driving uphill, through mud, sand, or off-road, where it is impossible to accelerate, such a motor will overheat. For example, when driving uphill 20%, a spherical direct drive motor on 6 kW will work at about 20% of its efficiency, and 80% will go to heat. In this mode, a powerful motor-wheel can overheat and burn in a couple of minutes, if it is not turned off in time (they usually implement an automatic shutdown of the motor based on a signal from a thermal sensor). This is not surprising: with a weak heat sink in the closed space of the motor and in low-efficiency mode, the windings heat up at the speed of a powerful electric kettle (4.8 kW to heat in our example with a 6 kW motor). However, so that the “kettle” heats up more slowly, you can “pour water” into it - some enthusiasts solve the problem with the help of water cooling .
Geared motor wheels
They contain an integrated planetary gearbox, usually having a gear ratio of 5: 1. They have lower weight with the same power, higher efficiency “on the bottoms” in comparison with gearless motors. However, mechanically less reliable (more moving mechanical parts) and do not support regenerative braking. But, most importantly, are not commercially available for capacities greater than 1000 watts.
They contain an integrated planetary gearbox, usually having a gear ratio of 5: 1. They have lower weight with the same power, higher efficiency “on the bottoms” in comparison with gearless motors. However, mechanically less reliable (more moving mechanical parts) and do not support regenerative braking. But, most importantly, are not commercially available for capacities greater than 1000 watts.
Central motors (middrive)
Middrives, as their name implies, is an external drive with a high-speed electric motor, usually installed in the area of ​​the carriage assembly, which transmits force through a system of chains, gears or belts. They make it possible to achieve the best power-to-weight ratio (the higher the motor speed, the easier it can be done with the same power). For example, aircraft model engines with a power of 6 kW can weigh only slightly more than a kilogram:
For comparison, the direct-drive motor wheels of the same rated power (Cromotor, Crystalite, Quanshun) weigh 12 (!) Kg. Also, the location of the motor closer to the center of the bike gives a more accurate weight distribution, allowing you to use such bikes, including for jumps and stunts. Can work in optimal conditions even on steep slopes and deep mud.
However, the power of the serial central motors for electric bikes is usually limited to 500 watts. The most powerful solution currently available is the 1500W Cyclone kit:
More powerful solutions based on central motors are collected by enthusiasts themselves, there are no serial ready-made proposals. When the creators of such powerful bikes this arises a number of technical problems.
Reduction For high-speed motors to reduce speed (from several thousand to 500-700) it is necessary to use a gearbox (there are no ready-made specialized gearboxes, each invents itself) or a chain / belt drive with a high gear ratio (making independently stars of the required diameter).
UPD: However, solutions are starting to appear .
Transmission . For high-powered engines, the standard chain from multi-speed mountain bikes is not suitable - it will simply break or will wear out very quickly. You must use a wide, solid chain for BMX single-speed bikes, a chain from a moped or mini-bike or a high-strength belt. And this often leads to the need to manufacture non-standard gears, bushings and overrunning clutch.
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Middrives, as their name implies, is an external drive with a high-speed electric motor, usually installed in the area of ​​the carriage assembly, which transmits force through a system of chains, gears or belts. They make it possible to achieve the best power-to-weight ratio (the higher the motor speed, the easier it can be done with the same power). For example, aircraft model engines with a power of 6 kW can weigh only slightly more than a kilogram:
For comparison, the direct-drive motor wheels of the same rated power (Cromotor, Crystalite, Quanshun) weigh 12 (!) Kg. Also, the location of the motor closer to the center of the bike gives a more accurate weight distribution, allowing you to use such bikes, including for jumps and stunts. Can work in optimal conditions even on steep slopes and deep mud.
However, the power of the serial central motors for electric bikes is usually limited to 500 watts. The most powerful solution currently available is the 1500W Cyclone kit:
More powerful solutions based on central motors are collected by enthusiasts themselves, there are no serial ready-made proposals. When the creators of such powerful bikes this arises a number of technical problems.
Reduction For high-speed motors to reduce speed (from several thousand to 500-700) it is necessary to use a gearbox (there are no ready-made specialized gearboxes, each invents itself) or a chain / belt drive with a high gear ratio (making independently stars of the required diameter).
UPD: However, solutions are starting to appear .
Transmission . For high-powered engines, the standard chain from multi-speed mountain bikes is not suitable - it will simply break or will wear out very quickly. You must use a wide, solid chain for BMX single-speed bikes, a chain from a moped or mini-bike or a high-strength belt. And this often leads to the need to manufacture non-standard gears, bushings and overrunning clutch.
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Cycling components
Bicycle components for a charged bike also experience increased loads and require careful selection.
Sturdy wheels
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Reinforced Forks
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Thus, the class of powerful electric bikes requires special attention to the components, many of which are too expensive or need to be improved. Specialized components for bikes, standing in the middle between the bike, moped and motorcycle, either do not exist, or they are just starting to be made. This creates certain difficulties, but also opens up scope for creativity.
Transport or entertainment?
Nevertheless, we believe that a powerful electric bicycle is a personal vehicle of the future that will gain popularity. Possessing all the practical advantages and speed of a scooter, it is more versatile and passable, maneuverable, silent, eco-friendly, cheap to operate. An electric bike can be stored at home, it does not need a garage or a guarded parking lot, as for a motorcycle or scooter, which is dangerous to leave for the night on the street.
However, this is not only a practical transport, it is also a great way to spend your leisure time: riding on a high-speed noiseless bike over rough terrain in enduro mode is an endless source of adrenaline. Also, unlike a scooter or a motorcycle, which with the onset of cold weather is put in the garage, you can safely ride an electric bike in the winter- A large selection of winter studded bicycle tires is available. Riding on a winter electric bike is an incredible feeling and a completely new entertainment, which, I am sure, will eventually gain its well-deserved popularity.
Ps.Photos of bikes and the production process, not included in the article, you can see here and here .
We hope that this story will not only inspire readers to get an electric bike, but also give confidence that creating your own material product in your free time is quite real.
Source: https://habr.com/ru/post/245943/
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