Electric Bike Buying Guide
- The * Original * Guide * steering the way since 2005 -
Welcome to the original electric bike buying guide (updated for 2015).
We want to share some of the things we have learned over the years. We hope you find it useful. You can always email us your questions to: firstname.lastname@example.org
When you mention electric bikes to the uninitiated they imagine what an electric bike must be like. I can guarantee that no one imagines the huge variations in performance and feel that are on offer.
When you are comparing traditional cycles it is quite easy to read the specification and look at the bikes to see what the differences are and where your money is going. With electric bikes the differences cannot always be seen, they are often electronic or contained in a format you cannot easily compare.
It is understandable to feel confused by conflicting sources of information. It takes years to truly understand all the technology used by e-bikes and the interplay between them and the resultant cycling experience.
The performance of an electric bike is not just about the latest battery technology (an over simplification), it's a combination of battery chemistry, control electronics, motor core composition, wire harness and connectors used, quality grade of all materials, efficiency of the system and attention to detail at the factory.
Just as motorcycles or cars that look the same can give very different driving experiences so can electric bikes. It is so important to test ride a potential purchase and get honest, knowledgeable advice.
You might be surprised by how the power integrates with your riding style. When the power comes in; when it cuts out and how smooth or aggressively it does both. Are the gears suitably matched to the power and for your intended use?
For instance, if you have weak knees and you have an e bike with a speed sensor and derailleur gears stopped in top gear you may find it very hard to start because you get least assistance while the pedals are turning slowly and of course you cannot change derailleur gears until you are already moving...chicken and egg anyone? This does not necessarily rule out this combination of components for people with weak knees...actually the advantage can be that you can reach full speed in a lower gear while applying minimal pressure to the pedals and therefore less strain to your knees. It will be important that the manufacturer has thought about the practicalities of their design and programmed the control unit accordingly.
The Chinese Effect
There are so many electric bikes on the market now that it can be difficult to choose between different brands and models. To add to the confusion many of the electric bike brands have bikes that look identical and have very similar specifications but widely varying prices and performances. Often we find the performance claims to be unrealistic. Electric bike components are not standardised like traditional bike components. This means if you cannot get a part from your retailer you may not be able to get a part at all.
The Chinese effect means that for every good successful motor or battery they manufacture there will be hundreds or thousands of low quality copies. It is impossible for importers or end users to tell the difference without thoroughly vetting the supply chain.
The European Effect
Europe is home to some of the largest and most powerful bicycle companies in the world. Very few such as Yamaha have been pioneers of electric bikes, most are recent entrants and in our tests some well known bicycle brands have performed poorly.
Not completely understanding electric bicycles these traditional cycle brands have played a clever hand. They have opted to use homogeneous (similar) systems to bring the purchase decision back to the bicycle components...something they and their dealers understand very well. This is having the effect of reducing the real assist options customers can find available to test ride. Some innovative products find it harder to get noticed. We continue to test non-mainstream products and will put the best all-round options in front of our customers so their purchase decision can be fully informed.
We feel the electric assist system should be the most important consideration for customers considering an electric bike purchase. After all this will have the biggest impact on the bikes capabilities - more so than the traditional cycle components.
The systems adopted by the large cycle brands are Bosch, Panasonic, Impulse. Can 3 drive systems really meet all peoples requirements? With years of experience serving e bike customers we know they cannot. Therefore there are others to consider alongside the industry giants, as well as the options presented with conversion kits.
Reviews: Journalists that have many hot topics to write about do not have the wealth of experience and feedback a professional electric bike dealer will have from serving customers and therefore their reviews can only ever be from a short term limited perspective of the products. Most publications will be influenced by their advertiser's wishes and some never even see the bikes they write about, leading them to feel safest championing big brands. This often leads to a rather boring machine being heralded as 'the best'. In reality there is no 'best' because the riding styles and performances vary so dramatically from machine to machine that each customer needs to try a few products to find the best for them.
Whether you are a keen cyclist or as good as new to cycling in this buying guide you will find the key information you need to help you buy the best e-bike for you. We guarantee this guide is supported by the best body of specialist knowledge and experience available for these products.
Comfort: is incredibly important when making such a big investment. If you do not feel comfortable on the e-bike it will not be used to its full potential. When you feel comfortable, and therefore in control and safe, these products can completely change the way you think about local transport or indeed what leisure cycling can mean for you. Many customers visit our stores with a bike in mind and after riding a few decide another bike 'feels' better. This is why we are the only business putting all of our resources into stores to ensure you have every opportunity to select the right bike for you.
Safety: comes down to the feel of the bike and the way the power integrates with your riding style and the terrain. Some pedelec bikes take a turn or two of the pedals before the power engages and therefore leaves you with the hardest work each time you start, this can lead to low speed wobble in traffic or on hill starts. Some electric bikes are too aggressive from the start and can be overwhelming or hard to control in tight spaces.
Maintenance: the ability to easily maintain the product really is paramount. Too many e-bikes are designed for looks and not for a long low cost practical life. They can have all major and peripheral components routed directly into the control unit, often making a (normally) simple motor wheel puncture repair half a days work. We see many signs of profit before customers, such as the use of non UK/EU standard bicycle components. Most of the highly acclaimed 'crank drive' systems have all of the working components in a single sealed unit. This makes a tidy system but....if a single component fails a customer must replace the whole unit at great cost. We feel that all aspects of a product need to be highlighted to ensure each customer makes the best purchase decision for themselves, pros and potential cons.
One example of a good way to check if an electric bike manufacturer or importer has put the customer first is to look at the electronic cut-outs on the brake levers. On traditional bicycles brake levers always get damaged. They are the first component to hit the ground if the bicycle falls over, they always get knocked against walls and caught on other bikes at parking bays. The same happens on electric bikes and this often results in the electronic cut-out switch in the brake lever being damaged and permanently stopping the motor from working. If you are a long way from your electric bicycle dealer (for example enjoying a cycling holiday) your bike may be out of action until you can get it back to them for repair. Brake levers often get damaged so a good bike brand will ensure they are easy for customers to replace. On many budget electric bikes we see in the UK, they are not easy to replace. Something worth considering when you are comparing models.
Reliability: The reliability of an e-bike depends on every single component, the grade of materials used to make the components and all the wiring inside and between the components. It also depends on the product being used within its performance comfort zone. Because of our experience with e-bikes our first 'golden rule' when selecting a product to potentially sell to our trusting customers, is to question its reliability. We test everything thoroughly and will not sell e-bikes we believe will fall short of our customers expectations.
Most of our customers have a budget in mind and our aim is to offer the best e-bike for each budget. The old saying 'you get what you pay for' is not always relevant here. We have seen a lot of over priced electric bikes that have serious quality issues. Regardless of the cost of your e-bike, we always ensure we have readily available parts (often in stock) so any issues can be sorted quickly. Cheaply made, rudimetary e-bikes tend to give the rider less control and have more 'technical issues' due to over loading of the lower grade components. In our experience cheaper bikes can be reliable if they do not try to deliver too much power. Components made from cheaper materials tend not to be able to handle regular high electrical loads without having issues at some point. If you have serious hills on your journey or luggage to haul then you need to think carefully about your requirements in order to choose an e-bike that will stand the test of time.
Advice: If you cannot try before you buy you may find it very beneficial to discuss your requirements with one of our e-bike specialists. They can match your needs to the available products with the benefit of many years experience, taking the full range of options and e-bike model specifications into account.
After-sales service: Having trained and knowledgeable staff to answer your questions, giving honest advice, and providing after-sales support is critical. We are contactable for support 7 days a week (via email when shops are closed).
Training a new member of staff takes us about 2 years. They need to understand bicycle mechanics, motor mechanics, electronics, general electrics and keep up to date with the diverse and rapidly expanding range of available battery technologies.
It is no easy task but we are committed to providing the highest quality overall customer service and after-sales support available for electric bikes in the UK.
Most traditional bike stores are not equipped or sufficiently knowledgable to support electric bikes once they have sold them. Try asking them to demonstrate the correct way to repair a punctured motor wheel, or how they would attempt a battery repair. How would they talk you through a power-loss issue over the phone while you are on your cycle holiday? Experience counts for everything, and we have been doing this day in, day out since 2005.
Buying: So how do you choose where to spend your money and ensure you get what you expect?
Most of our customers shop around and look online before coming to us, so we have learned a lot about what customers look for and what they expect.
So for you, the customer, it is important to learn a little about the important features of an electric bicycle.
The weight of an electric bike is essential to its performance, but what is a reasonable weight for an e-Bike? Cycling an electric bike without power should be no harder than cycling a traditional bicycle with a bag of shopping or a small child. The heaviest parts of an electric bike are the battery, the frame, and the motor.
Manufacturers have been busy reducing the weight of these parts, and if life was ever straight forward then the lighter bikes would be the best. However, life not being so easy, there are of course swings and roundabouts. Did you expect it any other way?
Frame: Lightweight frames are always good, unless you plan to do serious off-roading where a light weight frame sometimes sacrifices flexibility and strength. e-Bikes have to pass more stringent tests than traditional cycles.
Battery: Lightweight batteries are really coming along and in the more expensive bikes will usually provide power equivalent to the uncompromising heavy batteries. Beware though as some models do sacrifice power and battery life in order to reduce weight.
I explain more about batteries in a dedicated section.
Most dutch bikes weigh almost as much as some electric bikes and yet people cycle these every day without feeling the weight is too much of a burden. 'But the Netherlands are flat' I hear you say....and you are absolutely right - heavier bikes with good components are easy to cycle on the flat....as are well made e-Bikes. With e-Bikes you have power for the hills as well secure and safe handling. Within reason, the moderate increase in weight of an e-Bike is really not much of an issue. It may need greater consideration if you expect to lift the bike up a flight of stairs etc.
The weight of the electric bike will depend on the model selected for your intended use and e-Bikes specified with all the comforts for city use with cushy saddle, puncture protected tyres, mudguards, carrier, lights, chainguard etc will clearly be heavier than an e-Bike that comes in a stripped down format. The range you require (how far it can go on a charge) will also dictate the battery capacity and therefore battrey weight.
Here is a guide for city use based on required range. (To understand the Wh references please refer to the battery section.)
5-10 miles - 200Wh battery - 17-20Kg
20-40 miles - 300Wh battery - 17-22Kg
30-60 miles - 400Wh battery - 18-24Kg
40-80+ miles - 500Wh+ battery - 18-25Kg
The above weights are perfectly practical for electric bikes. When considering the battery capacity needed to achieve a required range, an allowance is made for winter performance drop and lifetime performance drop (batteries temporarily work less effectively in cold weather, and their overall performance decreases with age).
Motor: The component that provides a turning force to assist your pedaling.
Through continuous improvement and innovation, motors are becoming smaller but like any of the latest technology the best ones are more expensive. Better motors will have lighter more durable materials and sometimes they will be smaller in size and weight while still offering the same power output.
There are 3 main types of motors used on e-Bikes and there are pros and cons to each.
Brushed motors are not given good press. They are larger, heavier and noisier than their brushless counterparts and they need to be serviced. Doesn't look promising for the poor old brushed motors. However if you consider the ability to service brushed motors for a low cost (some at intervals of up to 8,000 miles) and that with this service the motor can continue as new your perspective may start to change. Brushed motors have proved to be robust performers, offering reliable hill climbing at a lower price point.
Brushless DC motors (BLDC) can be made smaller, lighter and certainly quieter than brushed motors. The technical differences are not as important as the relative performances under different applications. Well made sensorless BLDC motors have the same reliability as well made brushed motors - but without the noise and weight attributes.
Sensorless brushless motors are usually found in 3 phase (although there are a few 2, 4 & 5 phase) and are very similar in construction to AC induction motors which contain permanent magnets and are often used for industrial applications. We have noticed a significant improvement in the reliability of brushless motors since the introduction of sensorless hub versions. The hall effect sensors are no longer required because the position of the armature can be detected using EMF or magnetic field detection and this reduces the electronics required on board the motor.
*There is always an exception and for sensorless BLDC motors it is the friction drive systems which although even smaller, even lighter and even quieter suffer from slipping of the drive and the resulting activity in the electromagnetic characteristics can paralyse the control units. This comment is based on our experience of these friction drive motors since 2006 on the Protanium (Diavelo) and Schwinn e-Bikes, designed by Protanium and the Tongxin motors available from the same time and used on the 'Nano' kit systems.
Brushless motors have a linear power speed response which means that maximum torque is available from a standing start and reduces smoothly through acceleration.
Direct Drive motors, such as those used in the BionX retrofit conversion kits, are another type of BLDC motor and have the benefit of being completely silent (there is sometimes some very minor vibration under hard acceleration). We love the potential for smooth, torquey quiet assist of these motors.
Motor Power Ratings / Efficiency
Something that isn't mentioned often is the efficiency of a motor. What are we talking about when we state 200 Watts or 250 Watts, is it input or output power? Whenever power goes into a hub motor it drives the shaft which turns with a force measured in Newton Meters (Nm). The more efficient is, the more Nm you get for the same input power. The difference between the input power and the output power gives us the efficiency. Power is lost due to resistance in the copper coils, due to reluctance between the magnetic fields, due to the harmonics generated when operating. Efficiency is one factor that explains different performances of similarly specified e-Bikes. Ideally a low-medium nominal power such as 200 to 500Watts can be accompanied by a high peak power of say 1.5KWatts for the best all round performance. This gives you the power reach you might need without creating unhealthy demands on your battery system and your wire harness. Peak Power – this is the maximum power output a motor can achieve for a few seconds. It is a better indication of performance than than the nominal power which is usually quoted.
Position of the Motor
There are 2 commonly used drive positions for the motor on e-Bikes. You guessed it...there are pros and cons for both systems:
Why A Hub Motor?
With electric assisted and electric powered bicycles, scooters and motor cycles selling in the millions of units world wide – the huge majority of them using hub motors – hub motors have progressed from a peculiar way to power an electric vehicle to the one of the most useful and practical drive systems for electric vehicle (EV) applications.
For electric bikes, the advantages of a hub motor are:
1.The motor is in a space that is not otherwise used in the conventional designs of bicycles.
2.The motor can be installed without significant changes in the frame or the ordinary configuration of the machine making them perfect for conversion kits.
3.Hub motors are simple and self-contained, thus reducing overall cost of the vehicle by enabling the designer to use off-the-shelf parts and designs for their vehicle.
4.The motors are sealed and mostly maintenance free.
5.The motor is directly attached to the driven wheel, improving efficiency.
6.The centre of gravity is relatively low, improving balance.
7.It looks nice!
8.If it needs to be serviced, repaired or replaced it can be easily accessed.
9.If it does need replacing it usually does not affect any other component.
10.With hub motors we can replace one hub motor with an updated version if the old one is no longer manufactured. This ensures your product will never become redundant.
11.If you have a front hub motor then you can have a 2 wheel drive bicycle assuming you will provide human power to the rear wheel. This can have a number of useful consequences.
The Drawbacks of Hub Motors
For hub motors, the drawbacks are:
1.The cost is higher because the motor is more complicated than other kinds of electric motors.
2.Because the motor is sealed against water and dirt, getting rid of heat that the motor generates while turning can be a problem, luckily many controllers monitor motor temperature.
3.The wheel is heavier with the addition of the motor...by as little as 2.3Kg
4.There are hundreds of hub motor manufacturers in China and all of the motors look the same but only a handful are what we could call a reasonably made product.
Why a Crank Drive Motor?
Since Panasonic and Yamaha put their considerable commercial weightiness behind this type of drive system sales in Europe have rocketed. Sales in the US have been far slower due to the systems lack of how do I put it....grunt.
Despite the performance drawbacks crank drive systems can be the 'nicest' systems to ride.
Advantages of a crank drive system:
1.Standard lower cost motor design can be used with a single external drive shaft and a fanned heat sink casing.
2.The motor can be smaller because the fanned casing allows for heat to be more effectively released.
3.The motor is generally in or near the bottom bracket so the weight is low
4.The motor can be kept near its optimal operating speed by using the bikes gearing.
5.By using the bikes gearing the bike can provide more effective assistance on hills than same power hub motors.
6.Because of the low power levels used the systems tend to be reliable.
Disadvantages of a crank drive system:
1.The units are always sealed and contain almost all of the components, motor, controller, and torque sensor. This means if one component fails the whole system has to be replaced increasing the cost of maintenance and repair.
2.The systems are proprietary and if parts become unavailable it will be very expensive to adapt another system to fit.
3.The output power and therefore performance is limited by the strength of the chain and the sprocket. Standard chains and sprockets are used and these are designed for human power only, which means the amount of mechanical power that can be added is relatively small.
4.There will be increased maintenance on the drive chain, including all cogs and sprocket.
OK now you have found the honey pot!
Batteries are electrochemical and they have their own personalities, few battery packs are identical in their behaviour. 2 people can buy the same e-Bike model at the same time and have completely different experiences with their batteries. The differences between budget & well made e-Bike batteries are significant. As an example many of you at one point or another may have opted for a cheap generic battery over Duracell and realised that the economy is a false one for you and a waste of materials.
We have studied the theory behind batteries (this can keep you busy for a long long time) but the most useful information has come from our customers. No matter what the lab tests say there is no replacement for the dynamic testing of end users and all of that rich feedback we learn from and translate into the best services for our customers.
The electric bike industry has been waiting for your interest to become significant enough to allow more effective battery technologies to be offered at reasonable prices. That is starting to filter through and the following are the main pros and cons of the most frequently used battery technologies.
Sealed Lead Acid (SLA)
Pros: medium energy density, maintenance free, tried and tested on electric bikes, cheap.
Cons: heavy, battery cells can age quickly and die, no fast charge option, no storage option.
Nickel (NiMh & NiCd)
Pros: medium energy density, fast charge the norm, medium weight, serviceable.
Cons: Need interval discharges and servicing, suffer from memory effect, performance radically reduced in cold weather, no storage option.
Lithium-ion (Li-ion) If any store tells you that their e-Bike battery 'is the latest technology' ask them what that means. If they say 'Lithium' ask them which type of lithium ('ion' or 'polymer' refer to the electrolyte that holds the chemistry not the chemistry itself so don't accept those as answers) and what that means to the performance of the machine.
You need to discuss which Lithium chemistry suits your requirements the best, otherwise you may not get the performance you envisage and unsuitable use of the battery may lead to a shorter life with high replacement costs.
This is where it gets really interesting from now and into the future and some basic knowledge is required for you to understand the role of the differing lithium chemistries.
Energy is released when the ions (in this case lithium-ions Li?) move from the positive anode to the negative cathode through the electrolyte. The anode is usually graphite, the electrolyte is usually a solvent based lithium salt. The currently interesting and available chemistries are mainly focused on changes to the Cathode material which is usually a lithium based oxide. On e-Bike batteries you will currently see the following Cathode Oxides: Lithium Manganese LiMn2O4, Lithium Nickel Cobalt Manganese LiNiMnCoO2, Lithium Manganese Cobalt LiMnCo, Lithium Iron Phosphate LiFePo4.
The exception to the above is Lithium Sulphur LiS which uses a lithium anode and a sulphur solvent as a cathode. The potential for Lithium Sulphur is very exciting because each sulphur particle can hold 2 lithium ions compared to less than 1 ion for most other chemistries.
Talk to us about which lithium chemistry is the best fit for your requirements.
Pros: Very lightweight, very high energy density, durable, no maintenance, fast charge, can be stored.
Cons: Expensive, can be unstable, cells charge and discharge at different rates.
Pros: Lightest battery available, highest energy density, no maintenance, fast charge, proven high level of stability under extreme laboratory tests, flexible shape, low self discharge, can be stored if care taken, wide operational temperature range.
Cons: Most expensive, will suffer if incorrectly stored for a short time, can suffer thermal runaway and pose a fire hazard if charged after a period of incorrect storage or if the BMS has catastrophically failed, charging can be complicated.
HOW TO GET THE BEST FROM YOUR BATTERY
SLA: Like a car battery your lead acid battery takes a few cycles to get to peak performance, once there it should be topped up as often as possible. The reason you get a 3 year warranty with many car batteries is that they are being charged every time you run the engine and this means they rarely experience 'deep discharges'. The less full cycles you do the longer your SLA battery will last so top up when you can.
Nickel: NiCd and NiMh batteries are tremendously robust; they can deliver high amounts of current and be 'exercised' back to life when they start to die. As with most batteries the most important thing is to keep them topped up, however they are known to suffer from 'memory effect' or 'floating voltage'. To address this problem they need to have periodic full discharges and as they age the number of full discharges required each time increases. For a NiCd battery this period is every month and for a NiMh it is every 3 months. If a NiCd battery appears to be almost completely dead it may be brought back to health by isolating each group of cells and charging with very high currents, this should be left to someone qualified for the task.
Lithium: No matter which type of exotic lithium chemistry is used the battery maintenance follows a simple rule: keep it topped up! A lithium battery that will perform say 800 full cycles may well perform 2,000 half cycles. The trick is to get a bigger battery than you need for your journey or carry the (usually small) charger with you and take advantage of 'opportunistic charging'. Reducing deep discharge cycles increase lifetime and performance over the lifetime.
If the battery will not be used for more than 4 weeks it should be stored at a storage voltage of approximately 40% of it's operational voltage, e.g. a 36V battery should be stored at roughly 39V.
THE FUTURE BATTERY
Lithium batteries are the main focus for battery R&D; there are very good reasons for this such as: high energy density (energy/litre or Kg), low weight, flexibility of application, reduced internal resistance, longer life cycle etc
The greatest opportunity to improve battery performance lies in material science combined with chemistry and possibly even biology. The structure of the materials used engineered on the nano scale to provide a better environment for flowing ions or to work better with ions gives us plenty to be excited about. Research is even being done on the possibility of using proteins or more specifically amino acids to move the benchmark for rechargeable technology. This is clearly a very exciting field and if battery performance improves that is great - for electric bikes however the technology is already more than good enough and we guarantee to be able to upgrade our customers e-Bikes to the latest power packs if they wish to do this.
High Energy Density/Low Weight: The honey pot of honey pots! A number of companies and universities around the world are claiming that they can increase the energy density of Lithium based chemistry by over 10 times....that would truly speed up this pending transport revolution. Prof' Peter Bruce of the University of St Andrews in Scotland is one of the people claiming success in this area. Fast Charging: Many companies have now demonstrated technology for rapidly charging batteries, especially lithium batteries. There are products available on the market already and there are batteries designed to cope with the high currents required. Altair Nano and Toshiba have developed lithium batteries capable of taking huge currents without thermal overload. The key is the low internal resistance and without getting too technical, both companies achieve this by eliminating graphite in the porous separator and using nano engineering to bond with more lithium ions.
Long Life: a bonus of low internal resistance is that an increase in longevity occurs. Battery life spans are normally related to the number of full charge and discharge cycles a battery can do before it looses 30 to 40% of it's capacity. Altairs Nano Titanate battery has now achieved over 20,000 cycles and Toshiba's has achieved 9,000. In the future you may well have to include your batteries in your will!
What exactly is an electric vehicle (EV) battery?
An electric vehicle battery is a high current battery. This is very different from most consumer electronics batteries. And the EV battery is much larger, with much more energy stored. (Do NOT test EV batteries by putting your tongue on the contacts! And do not short the terminals to see if you get a spark!)
Keep in mind that good EV batteries have enough energy to carry a 90 kg man over hill and dale for close to 20 miles. That is a LOT of energy!
A battery is not just one solid piece, but a collection of ԣells". The cells are one complete unit of anode, cathode and electrolyte that produce electricity from a chemical reaction in the cell.
Each cell type (also called a cell's ԭetallurgyԩ has a nominal voltage. For example, NiMH (Nickel Metal Hydride) is about 1.2 volts per cell and thus we need to combine a bunch of cells to get the voltage we use in an electric motor. So 30 cells gives us 36 volts (not exactly – but you get the idea) and we have a useful voltage. For comparison, Pb (Lead Acid) is 1.5 volts per cell.
How do you measure a battery's capability?
Usually, when people ask about a battery's capability, they want to know two big things:
The amount of energy stored in the battery's cells. (How far can I go?)
At what rate the cells discharge electricity. (How much power and speed?)
Amp Hours are the most common way to describe the amount of electricity in the cells – and all that talk about Էatt hoursԠis really the same thing, times the voltage (Volts x Amp hours = Watt Hours). The capacity of one cell in Amp Hours is also the capacity of the entire battery in Amp Hours. One 7 amp cell is 7 AH at 1.2 volts. If you need 30 of them to get your required voltage, you still only have 7 Ah in usable energy – at that voltage.
To put this another way: More Amp Hours means you can go farther, at higher speeds and up bigger hills. But more Amp Hours usually costs more money, and weighs more. Also in our experience you rarely get the Amp Hours stated out of the cheaper batteries. In fact you hardly ever get close.
Max current means essentially Ԉow fast can the cell discharge energy?ԠThink of it as a can full of water. The can is the cell, the water is the electricity – the larger the cell, the larger the amount of water – and the water flows out of a hole in the can. The larger the hole, the faster the water can come out. In terms of a battery, if the discharge (the hole) is not big enough, then the motor may not be able to get enough energy (the water) to function at Max performance.
You could also think of the Max current as Ԩow big the fuel line is".
Some people will describe Max current in terms of Max amperage that the cell can endure and for how long. Another way is to describe it in terms of ԃԬ or ԡt what rate can the battery be discharged for one hour = 1C. An example is: If a battery can be discharged at a 10 amp draw and will last for one hour, than it is a 10Ah battery at 1C.
What are some problems with battery construction?
Most consumer electronics battery applications use a tiny handful of cells. For example, a cell phone battery could be 3.6 volt, three NiMH cells in a battery inside a plastic case. In EVs, there are usually more than 30 or more combined cells. Each cell is connected to another with a small tab of metal called a ԣonnector.ԠEach connector is a potential point of mechanical failure, and a small resistor.
Large packages of cells also create heat problems. A cell buried inside of several layers of other cells has no way to easily shed heat developed during charging or discharging. Heat leads to failure, diminished performance and longer charging times.
What are the solutions?
Each battery type has different capabilities, needs, and limitations. So, very careful engineering tailored to the type of battery being used is needed.
There is a trade off in terms of cost, weight, capacity, system complexity, and safety involved in all battery engineering choices. All of these factors must be brought in line with one another to create a safe, sound solution.
A big part of preventing catastrophic failures (like the kind that burn down houses) is a Ԣattery management system". This BMS component is what prevents the cells from over-discharging, overheating, charging incorrectly, and other things that could cause problems. The BMS also manages cell charge and discharge to get optimal performance and life from the battery package. Physically, this is a printed circuit board with a complex and often IC-controlled circuit.
N.B. You may have heard of ҥxploding batteriesҠon laptops and spontaneous combustion of mobility vehicles. These have been caused by instabilities in cheaply made batteries built without fire-preventative systems. If you want the benefits of a Lithium battery it is advisable that you do not try make your purchase decision on price alone. It is important that Lithium batteries are supported by a battery management system which regulates each Lithium cell individually and maintains the stability of the chemicals, charge and temperature.
Almost all lithium battery batteries will have an on board or charger based BMS, however many of them do not include a cell balancing function which is required if the useful life is to be maximised.
Cell Balancing is a process that prolongs the usable life of a battery by ensuring the cells within a battery pack contain a similar amount of energy and therefore a low voltage cut off on one cell doesn't trip the BMS when there is still lots of energy in the other cells. A cell that has a higher voltage can also stop the charging before the other cells are fully charged. This situation tends to be exacerbated by time and use unless cell balancing is incorporated into the design. Currently few e-Bike batteries include this feature.
You can find the battery in numerous places on e-Bikes and there are some considerations for each position as follows:
Behind the seat post: The most common position for the battery extends the bike length by 10cm to 18cm. The weight is central and low and the battery size can be large for longer range products.
In the pannier rack: The second most common place for the battery places the weight higher on the bike which does make the ride feel different. The battery and rack have a tendency to rattle although less so if the rack is a solid part of the bike frame. Especially with 36V 10Ah lithium batteries we have seen the rack wobble a lot and in some cases the racks have broken. In our experience if the pannier rack is bolted onto the frame 26Ԡwheel and larger bikes should have no more than a 24V polymer battery in the rack. 20Ԡwheel or smaller e-Bikes have been fine because of the shorter rack stays. It is possible to hide the battery by having pannier bags but take note that many of the rack batteries restrict the use of clip on pannier bags so you will have to use the throw over tie on pannier bags.
In the frame: allows you to hide what you ride by having a concealed battery. We find most customers are now quite happy to openly cycle an electric bicycle. It can help with the styling of the bike, great examples being the Gocycle and the Ultramotor Metro. In most cases you will have to charge the battery on the bike and cannot carry a spare to extend your range if required. The range of the machines can be limited by the space inside the frame.
In Luggage: as offered on our Brompton Sparticle and other systems including Heinzmann handlebar, pannier or other luggage bags can be used to carry the battery and other components. This gives flexibility with positioning and keeps weigh down. It can be quick to remove but awkward to secure.
OK you will probably never have to see the controller (at least I hope you do not buy an electric bike where you need to) but it is such an important component and the performance and the longevity of the electric bike depend on it. It is best to think of it as the brain of the machine!
Simple controllers just act as a gateway for a signal between the pedals or the throttle, and the resulting supply of power from the battery to the motor.
More complex controllers carefully assess a varying array of rider and environment data to optimise the performance, increase the safety and the life of the bikeӳ components.
Controllers use the systems voltage and current to regulate speed and range.
Generally speaking an electric bike with a higher voltage can supply a higher current. This means that the bike will offer more torque, acceleration and speed. However a higher current will drain the battery faster and here we really get into more swings and roundabouts: if the powerful (and more useful) electric bikes draw more current they need larger (and heavier) batteries to have a practical range.
It is a fine balancing act and the quality of the controller really does make a big difference to the performance of the electric bike. The best way to judge is to ride.
The 'feel' of the ride is a result of the inputs to the controller, how the controller interprets the signals and then by the output it is programmed to give to the motor.
Inputs to the control unit vary but usually include a speed/cadence sensor or a torque sensor, a throttle, an assist level selector and may include such things as a gyroscope incline meter, a speedometer, a motor rpm sensor, a light level sensor.
Speed/Cadence V's Torque Sensor
For electric bikes that include pedal assist they will either sense the pedal speed/cadence or the torque/pedal pressure applied by the rider and then translate that into output to the motor based on an additional assist level selected by the rider.
The speed/cadence sensor uses the cadence of the riders pedals to decide the power assist output. The faster the pedals are turning the more power is supplied. Some e-Bikes use the sensor as a switch so once the pedals are turning the power engages to the maximum assist level you have selected. Others give an amount of initial boost to gain 'safe' momentum and then match your preselected maximum assist level. Some actually require you to pedal faster to go faster which doesn't allow for gear changes.
Torque sensing can occur in the crank/bottom bracket or from part of the drive chain or motor. Anywhere that the riders pedalling force can be detected and fed to the control unit. The control unit should then constantly monitor the force applied by the rider and respond with a preselected level of assistance up to the maximum selected by the rider.
Torque sensing allows for a smoother more controlled ride but this is not always the case. e-Bike manufacturers have often misunderstood how customers use the products. There is more information to process and manufacturers do get it wrong.
Both pedal assist sensors can be used to great effect and we have seen many terrible products using both incorrectly. Urban Mover e-Bikes at the time of writing use a torque sensor that works by using a spring loaded chain wheel that gives a little with every rotation. It becomes quite irritating after a while. Some electric bikes use both torque and speed sensors.
At the end of the day because the difference is often software related the only way to judge is to test ride. It's more fun than reading all the specifications too.
Controller Functions in the bike description: here we try to give you an idea of how you will control the bike. It cannot explain how the bike responds to your inputs.
Throttle: twist grips or thumb throttles come in many varieties. Some include button options and battery gauges others do not. You can have full length twist grips or half length twist grips. Our customers usually have a personal preference for either thumb throttle or twist grip depending on which feels more comfortable. On conversion kits thumb throttles may be easier to fit alongside your gear selectors and take up less handlebar space but twist grips are more intuitive to use.
Half length twist grips tend to be more robust because they are less likely to get damaged when the end of the handlebar hits something and when you are on full throttle for a sustained period half of your hand can hold the grip and take the strain of the throttle spring back.
Pedal Assistance: this section tells you if a torque, speed or a combination sensor is used and how many levels of assistance you can choose. The more levels you can choose the more control you have over the performance.
ON/OFF: some electric bikes are immediately ON once the ignition is turned on. If possible it is nice to have this option ready to use on the handlebar so you can power up and down without stopping the bike. If you see this option in the 'controller functions' section then you know that you have control of power from the handlebar.
Lights: if you have an integrated light or lights and you have a handlebar control for them or they will come on automatically 'auto'.
Standard Bicycle Components
Electric bikes come in 2 distinct forms: those that look and feel like traditional cycles and those that want to be something different. The e-Bikes trying to be different can be so in an effort to fulfil a niche need such as transporting children by bike (unfortunately taking children to school by bike is still the exception rather than the rule) or it may be an effort to look like a scooter or just to stand out.
Scooter styled e-Bikes: will not be offered in our range because they are only made for the Chinese domestic market and contain many none standard components that you will struggle to find in the UK. These include 36V light bulbs, unusual size inner tubes and tyres (imagine your machine being resigned to scrap because of a puncture or tyre thread wear), unusual bottom brackets and nut and bolt sizes. Because of all the plastic the maintenance and repair costs are greatly increased.
Brakes: You may go through brake pads faster on an electric bicycle because you have a little more weight and tend to reach a higher speed between stops. We often see unusual brake components on electric bicycles we test. Importers should ensure standard UK/EU bicycle components are used so your machine will be easy for customers to keep on the road and maintain.
If you want low maintenance then hub or roller brakes should be considered but always look for a well known brand. Shimano make some of the best roller brakes with their IM70, IM50, IM30 etc. They need little maintenance and performance is unaffected by weather or long downhill runs where breaks usually heat and lose efficiency.
Disc brakes: can be great but on budget e-Bikes the V brakes you can find are generally more effective than the low quality disc brakes.
V brakes: the standard brake system is good value and generally works well as long as your rims are kept free of dirt and oil. Tend to be a safer bet on budget e-Bikes.
Lights: Integrated lights often seem like a good idea but they should be avoided on all budget or value e-Bikes. The problem is two fold: they will often use 24V or 36V bulbs which cannot be sourced in the UK and if the lights short out there is a chance they will cause expensive damage to the control unit.
Gearing: we have been trained over the years to think that 'the more gears the better'. This isn't true and it is especially wrong for most electric cycling purposes. It is not the number of the gears but the correct ratios that matter and when you can call upon the power you are unlikely to need as many gears. For most people in relatively flat areas 3 well spaced gears will be sufficient (an easy low, a sweet middle, and one that allows rider input at and above the top powered speed). So many electric bikes have incorrect gearing at the top end so your legs are flapping like chicken wings if you want to add to the top speed. It is worth having a test ride or discussing your requirements with us to ensure you get the right gearing. If the top gear is too low we will state 'under geared', which will be of interest to those wishing to pedal and add something at the top speed.
Derailleur: These are the most common form of gearing and they do the job assuming the correct ratios. They are effective and cheap. They require high levels of maintenance and need to be cleaned and serviced regularly. On folding electric bikes they are easily bent if the bike is not stored carefully. You cannot change the gears without pedalling so you may have to start in a gear that is uncomfortably high.
Hub: Heavier than derailleur and more expensive but requires minimum maintenance. The gears are in the rear hub sealed away from water and dirt providing the smoothest gear changes. They can be changed at any time ensuring you can always access the best gear when you need it. More practical for electric bikes. The Shimano Nexus and Alfine hub gears are considered the best with the exception of the amazing Rohloff 14 speed hub.
Du Vinci: variable gearing is rarely found on electric bikes because of it's added weight. It offers theoretically infinite gear positions within its maximum and minimum ratios.
Suspension: varies from almost imitation to excellent quality and adjustable travel. The travel is the distance a fork can compress to absorb shocks. The bigger the travel the more cushioning potential.
Headset: A headsets are generally less adjustable than quill type headsets. However the rule is the more ways the headset can be adjusted the easier it will be for you to find a comfortable riding position. There are also tool less adjustable quills which allow you quickly change your riding position whenever you feel a change would be good. Our customers have given us great feedback about this.
Saddle: ranging from sport to comfort to super comfort. Saddles are easily changed unless we specify otherwise so this may not be a critical point for your purchase decision.
Pedals: what can we say about pedals you may wonder. There are of course grades of quality and style but nothing that we can warn you about on traditional pedals. It does however get a little more interesting for folding pedals. There are various ways a pedal can fold and there are only 2 we have found that do not get stiff and difficult to use. The simple rule is that the pedals must fold without your fingers squeezing a trigger or turning a stopper. these eventually become stiff and require superman's fingers.
Stand: side stands or centre stands to prop your electric bike up while you are not holding it. The quality varies with some stands flexing too much and allowing bikes to easily fall over. Some side stands lock into place to prevent your expensive bike from falling over. If you are loading and unloading shopping, other luggage or children then a centre stand is best because it is more likely to hold the e-Bike in an upright position. On most e-Bikes we can change the stands to suit your intended use or preference.
Luggage Capacity: this includes the ability to add handlebar bags, pannier bags and the ability to avail of all the options a traditional bicycle can avail of. These include handle bar bags and baskets; low riders, pannier bags both clip on and throw over, rear basket, rear shelf.
Child Carrying Capacity: can the machine be easily adapted to carry children on board or tow in a trailer? If yes how many on board and towing?
Main Options: if the electric bike comes in a number of versions where the fundamental concept, performance and most of the components are shared we will let you know in this section. If possible we will make an easy link to see the other versions. If the options are very close they will be listed on the page or with more information in attachments. An example would be having a step over (gents) and a step through (unisex) version of the model.
Special Features: usually this will refer to a feature of the electrical system such as a boost button, an off road extra speed feature, or regenerative feature. More information about these features can be found in the Controller section of this guide.
Suitability for heavier riders: this is indicative of our customers experiences. The bikes that have had the least number of weight related faults or issues such as spokes snapping or coming loose or worse. Since 2005 we have kept careful records of all faults and causes on every bike we have tested and sold. Most e-Bike brands suggest a maximum rider weight should be within 100Kg (15st 10.5lbs). A few have been easier to work with when heavier riders have had potentially weight related issues. We take this into account in our recommendations.
Rider height: here we endeavour to give simplified but realistic information about suitable rider heights for each product. We use s, m and t for small, medium and tall. Small = 5' or 152.5cm up to Medium = 5'6Ԡor 168cm up to Tall = 6' or 183cm up to 6'5Ԡor 195.5cm. This is approximate due to frame styles etc. so test riding is advised. We have options for cyclists above 6'5Ԡand of course for cyclists shorter than 5', please contact us for details. We can also select suitable traditional cycles and electrify them if that proves to be the best option for you.
Towing: Can a trailer or children's tag-a-long bike be attached to the seat post or rear axle and towed with or without modification?
Security: How many points on the electric bike allow a D lock or chain through the frame to be secured to something. What is on bike battery security like?
Safety: Any safety equipment or functions on the electric bike such as brake cut outs.
Warranty: details the warranty on the major component sets. Please note manufacturers may change this at any time so our information despite our best efforts may not always be up-to-date.
The specification of an electric bike can rarely be translated into relative performance because so many important details are not referred to. This makes it very difficult for you the customer to make a decision based on reviews that rarely mention these details.
Performance relies on more complex details such as the composition of the controller (e.g. how many mosfets), the capacity of the controller shunt, the grade, gauge and condition of the wiring loom (also known as the wire harness), the composition and grade of the motor materials and of course the battery's ability to deliver and sustain the required current and the ability of all connectors to handle the current and make clean weather protected contact. For some uses the systems ability to deal with internal heat or peak voltage drop will be real barriers to increased performance.
By testing every distinctly different electric bike on the market we have the best knowledge to help you make a relative decision. In the performance section of this guide we will give you relative information such as: 'hill climbing' ability out of 5 where 0 is amongst the worst hill climbers we have tested and 5 the best. We hope this information will allow you to make better purchase decisions with your intended use in mind. The most sought after information will be in the 'summary' section at the top of each product description.
Suitability for hills: many customers are surprised when we suggest that most electric bikes may not give a satisfactory performance on hills. To handle the increased loading that regular hill climbing requires the components have to be made of reasonable quality and the whole system needs to be geared towards the performance required. Some e-Bikes will be fine on hills for a while but continuous use outside of their comfort zones will lead to problems. Our rating is 0 for worst hill climbers we have tested through to 5 for the best.
Range: hardly ever what the websites and brand marketing material claim. We rate them for use on the flat once batteries are worn in with a rider between 70Kg and 80Kg. The tyres are at the higher end of the recommended pressure with all drive chains and bearings in good condition and minimal weather interference. On pedal assist we will use a medium assist level. If there is a throttle the lower of the range will be throttle only after pedal assisted starts and the higher would be the pedal assist range, e.g. 20-30 miles.
Power in/out: The way electric bikes integrate the power varies dramatically from smooth to aggressive. A smooth integration would have the power taper in and out while an aggressive integration might have exciting acceleration but an uncomfortable drop off at the top speed followed by a delay before the power comes in again. There are so many variations on the power in and out and we will do our best to give a relative and useful description.
Weight: many people consider weight part of the performance. Electric bicycles are very light at 20Kg-24Kg often weighing less than traditional German and Dutch e-Bikes. Given good bearings and drive chain they are perfectly easy to cycle without the power. The lithium powered 2 wheelers range from approx 14Kg (Gocycle) to 35Kg. Costing less lead acid powered e-Bikes can be heavier approaching the legal limit of 40Kg. We always quote weight inclusive of battery.
The electric bike wireharness is the wiring loom that carries power and signals between the e-groupset components.
It won't be often a feature of any discussion you have with your electric bike dealer - and hopefully it won't be important but as another way to check the thought gone into the product you are considering check out the wireharness.
In particular - how thick are the power wires (they should be at least 14AwG), are there convenient connectors near peripheral components for fast repair/servicing, is the control unit a mess of wires (messy configuration reduces the likely hood that the exact configuration can be supplied in the future if a replacement is required), is the cable routing sensible (will they guide drops of water directly into the control unit or snag anywhere).
It doesn't take long to make a few simple checks based on the above information and it can make a huge difference to your long term enjoyment of your purchase.
I hope this guide will prove useful. If you have any questions or suggestions please email to: Support@ElectricBikeSales.co.uk