1 E-MTB motors have a rated continuous output of 250 watts. In reality, however, the drives deliver 500 watts and more. What is behind this?
Although the rated continuous power of 250 watts is often mentioned, it does not allow any conclusions to be drawn about the actual peak and continuous power of a motor. The reason for this is a trick in the European test standard for pedelec drives. This standard primarily limits how much a motor may heat up during the test procedure. The power output is only of secondary importance. The regulation is: During the 30-minute test procedure, the motor must heat up by exactly 20 degrees. The test is carried out on a test bench without cooling and at room temperature. Firstly, this test standard gives manufacturers a great deal of leeway.
The operating point at which the engines are tested on the test bench is not permanently defined, but is linked to the manufacturer's recommendations. Secondly, in practice, the motor is cooled by the wind in many situations and can also become significantly hotter than just the 45 degrees resulting from the 25 degrees room temperature in the test procedure and a maximum heating of a further 20 degrees. In practice, this already enables classic e-MTB motors from Bosch, Shimano, Yamaha or Brose to achieve peak outputs of 500 to 600 watts. Particularly large and heavy motors such as TQ's HPR 120, where the housing can absorb a lot of heat, even deliver peak outputs of over 700 watts and still maintain the 250 watt rated continuous output.
In our E-MTB special "All the facts for beginners" you will find even more useful information:
2 How long does an e-bike battery last?
Two phenomena determine the ageing of a rechargeable battery. Cyclical ageing, i.e. ageing due to charging and discharging, is particularly important for batteries that are used on a daily basis. It is less relevant for most e-MTBs. However, the e-bike battery ages over time even without use. This is called calendar ageing. As a rule of thumb, a lithium-ion battery should last four to five years in normal use. However, wear and tear then becomes increasingly noticeable. However, the battery can also age much faster. For example, prolonged heat - such as during storage - accelerates calendar ageing.
The battery should therefore rather:
- lying in the cool cellar than standing outside in the sun
- should not be charged at temperatures below ten degrees
- not be stored in a completely full or completely empty state
3 What role does weight play in the range of e-mountainbikes?
If the E-MTB is not only used on flat terrain, the weight is the most significant factor influencing the range. In contrast, air and rolling resistance play a much less important role when travelling uphill. Imagine it like this: On a tour with 1500 metres of elevation gain, it is as if the motor had to lift the entire weight of the rider, bike and equipment by 1.5 kilometres with a little help from the rider. The altitude range shrinks almost proportionally to the system weight.
The explanation: The motor delivers a certain amount of wattage for a certain period of time until the battery is empty. However, it pushes the heavy system forward much more slowly with this power. In the limited time that the motor can deliver its wattage, a heavier system weight (rider + bike) will therefore climb fewer metres in altitude than a lighter system weight.
A concrete example: The difference between a system weight of 85 kilos (60 kg rider + 25 kg bike) and a system weight of 115 kilos (90 kg rider + 25 kg bike) is 26 per cent.
If weight were the sole influencing factor, the lighter system weight would take you 26 per cent further or higher in the time it takes the motor to deliver its power (until the battery is empty). However, as other factors, such as rolling resistance, also have an influence on climbs, the difference will be somewhat smaller in practice. The flatter a route is, the less the system weight affects the range/reach height and the more air and rolling resistance become important. Ergo: the steeper the hill, the more drastically the kilos become noticeable.
4 Battery capacity of an E-MTB in the cold?
Cold inhibits the flow of ions in the battery. It can actually be the case that the battery switches to "empty" at temperatures below ten degrees, but you can still ride a good distance when the battery has warmed up again. In winter, therefore, warm the battery to room temperature before setting off. Then call up the power right from the start and do not take any breaks so that the battery does not cool down during the journey.
5 Power and torque. What is the difference with the e-bike motor?
The torque (Newton metres) stands for the force of the rotary motion (physically: force times lever arm). With E-MTB drives, the highest torque is applied at low speed, so that the bike pushes powerfully from the start. The torque decreases as the cadence increases. The power (watts) is the product of torque and speed. On an E-MTB, it determines how fast the bike can climb a hill. The motors usually only deliver maximum power at pedalling frequencies of 75 to 90 revolutions. - Robert Kühnen, graduate engineer
6 What does the frame geometry say about an E-MTB?
Can you judge the riding characteristics of a mountain bike from a standing start? The frame geometry provides some clues. Long chainstays, a long reach or a slack steering angle make the wheelbase longer. This tends to make a bike more stable and gives you more confidence at high speeds. Shorter values and a steeper steering angle make the bike more manoeuvrable.
7 What influence does the assistance level have on the range of an e-bike?
Remember: your battery always has the same energy content (watt hours). Regardless of whether you are travelling in Turbo or Eco mode. Whether you are flying up the mountain at full throttle or only travelling half as fast and for twice as long is almost irrelevant for the e-drive. - Dipl.-Ing. Lutz Scheffer, developer at ADP/Rotwild
Lutz Scheffer explains further: "The difference in the reach height is due to what you as the driver contribute to the reach height. For example: In turbo mode, you might manage 1200 metres in altitude on one battery charge. In this case, the motor delivers around 450 watts of power and you pedal at 150 watts. The motor then does three parts of the work and you only do one part with your legs. So for 1200 metres of altitude, 900 metres of altitude are covered by the motor and 300 metres of altitude by you. If you now switch to Eco, you will be pedalling with your legs for the same amount of effort as the motor delivers. Namely around 150 watts each. The motor then works out 900 metres in altitude as before. But because you ride much slower and therefore longer, your legs also contribute 900 metres of elevation gain. This results in an idealised calculation of 1800 metres in altitude. Conversely, this also means that if you want to extend your turbo range by more than a third, you have to be really economical with the battery or plan for an extender, second battery or charging stop."
8 Battery development: 1000 watt hours and more without adding weight to the battery. When will this be possible?
This question is answered by Dr Christian Kupper from the Karlsruhe Institute of Technology (KIT): "To generalise, you can say that there is still a lot of room for improvement when it comes to batteries. By optimising classic lithium-ion batteries, it may be possible to achieve 30 percent more capacity with the same weight as today. Solid-state batteries have even more potential. In the long term, we expect one and a half to double the capacity of today's batteries. These batteries also have other advantages, such as longevity and safety. The topic has been well researched scientifically, but putting it into practice will still require a lot of development work. It is difficult to say when these systems will be available on the market. But if the first premium car manufacturers start using solid-state batteries in five to ten years' time, then e-bikers could very quickly become the direct beneficiaries of this development."
9 Will e-MTBs become cheaper again?
Sales of high-quality e-MTBs, which are interesting for sporty use, are still quite stable. There is still a lack of branded parts, which is still leading to delays in delivery. It is therefore unlikely that the situation will ease here. However, sales of entry-level and mid-price e-bikes have fallen since last autumn. There could actually be an oversupply here in 2023, which could prompt less prestigious manufacturers in particular to offer substantial discounts. - Jo Beckendoff, business and industry expert
10 Visible damage to the e-bike frame - can you still continue riding?
Unfortunately, as always, it depends. A superficial scratch in the paintwork or a slight dent in the aluminium frame is not a problem. Bicycles have become very safe these days. Nevertheless, it is worth checking the bike regularly for damage when washing it - ideally simply with a bucket of water, cloth and brush. If there are real cracks or major deformations, you should take the bike to a specialist and, if in doubt, leave it for the time being. - Dipl.-Ing. Dirk Zedler, bicycle expert
11 Pedelec or e-bike: what's the difference?
Pedelecs are what are colloquially known as e-bikes. In other words, bicycles on which you have to pedal yourself to get assistance from the motor and which switch off the motor at speeds above 25 km/h. All other motorised two-wheelers are subject to compulsory insurance in Central Europe. They require a licence plate and may not be ridden off-road. They are therefore of no interest for off-road biking.
12 Can e-mountainbike batteries explode?
Modern batteries have become very safe. However, there is a very, very small residual risk, especially if the battery has been damaged. The electrolyte, i.e. the material through which the ions in the battery flow between the cathode and anode, is flammable and can ignite as a result of a short circuit, particularly when charging. However, this is extremely unlikely with undamaged branded batteries. However, anyone who has concerns after a fall or water damage should have the battery checked by the manufacturer. - Dr Christian Kupper, Karlsruhe Institute of Technology (KIT)
13 Is it possible to buy used E-MTBs?
Buying second-hand can be a good option, especially in times of constantly rising new prices. However, as with a bike without a motor, buying second-hand is a matter for experts. In addition to the condition of the frame, wearing parts and suspension elements, you also need to be able to accurately assess the motor and battery on an e-MTB. The safer alternative to buying second-hand: a refurbished bike from a professional supplier. These bikes are at least thoroughly and professionally checked and, in addition to a right of return, the providers also offer a warranty that is often on a par with a new bike.
14 How far does the battery last in practice?
Christoph Malin, photographer, Vertrider founder and E-MTBer from the very beginning, believes: "It's difficult to give generalised answers because so many different factors influence reach. The most important factor is weight (see above). A small and light rider will go much further with the same battery than a large and heavy rider with a lot of luggage. At 85 kilograms, I'm not the lightest and often have a heavy photo backpack weighing up to 25 kilograms with me. With a 625 Bosch battery, I usually manage around 1300 metres in altitude on short but steep tours around Innsbruck. I ride with medium support when it's flat or rolling well. On rough gravel or steep climbs, however, I sometimes treat myself to an e-MTB or turbo. If the tour is longer than 1300 metres in altitude, I like to use the dual-battery system. A charging stop or a second battery would be the alternative. My tip: it's best to try it out for yourself. Ride a typical tour several times, each time with different levels of assistance. Ideally until the battery is completely empty. This will give you a good feeling for the maximum range with your parameters and when you need to start consistently saving battery power."
15 MTB and E-MTB: Does it make a difference to riding technique and setup?
Good riding technique is good riding technique. Whether with or without a motor. However, I do recommend flat pedals for e-MTBs, even for proven clickie fans. They provide more safety in the long term and you don't get used to an unclean technique. Tyres with a DH casing provide excellent damping and generate a lot of ground contact. This provides safety off-road, and the disadvantages in terms of rolling resistance are negligible with a motor. If you also want to tackle sporty uphills, you should specifically train your balance on an E-MTB. Trackstands are the method of choice here - you can practise at any red light. - Stefan Herrmann, EMTB riding technique expert
16 Who is stronger? E-biker or cross-country pro?
Even a perfectly trained cross-country pro can only deliver more power than an e-biker with motor support for a short time. The professional may be able to produce the 650 watts required for two minutes. In a sprint, a pro can also achieve peak performances of 1500 watts. In the long term, however, the power limit of a professional is around six watts per kilogramme, i.e. around 400 watts. Although the cross-countr y pro has to move significantly less weight on his race bike: On a long climb, an averagely trained, lightweight e-biker pulls past in turbo mode. For heavier riders, however, things can get tight. - Robert Kühnen, graduate engineer
17 Why don't all e-bikes charge with the same battery chargers?
Due to different designs, the batteries require different charging currents. By using their own charging ports and chargers that only fit these charging ports, manufacturers prevent the battery from being charged with the wrong charging current and being damaged as a result. The alternative would be standardised charging ports, such as the USB-C standard, which is familiar from smaller electronic devices. These ports are more complex and enable intelligent chargers to communicate with the battery. This also prevents incorrect charging currents, but is more expensive to design and produce. As chargers are not yet a key selling point for e-bikes, manufacturers are not making the effort.
18 Travelling with an E-MTB: What works, what doesn't?
The e-MTB battery is considered dangerous goods. It is therefore not possible to fly with an e-bike. An option for air travel may be a rental battery in the holiday destination. E-bike transport is also partially excluded on long-distance coaches. On the other hand, e-bikes are generally not a problem when travelling by train if you inform yourself in advance. On the rear carrier of a car, you should pay attention to the payload and coupling load. If in doubt, it is worth removing the batteries and transporting them well protected, individually in the boot.
19 Permitted total weight for E-MTBs: What does this mean? Do I have to fear a defect if the weight is exceeded?
Mario Pöss, designer and developer at Focus Bikes, clarifies: "The permissible total weight is the maximum weight that the bike, rider and any luggage may weigh together. In our case at Focus, for example, this is 150 kilograms for most E-MTB models. With a bike weight of around 26 kilograms, this leaves around 124 kilograms for the weight of the rider and equipment. This is the weight at which the frame and components were tested in the laboratory, and we also provide a warranty up to this weight. If the permissible total weight is exceeded, the warranty no longer applies. However, this does not mean that the bike will immediately break if you slightly exceed the permitted system weight. Above all, if you only roll through normal road traffic with a bit of luggage, little is likely to happen. However, if you are still at the limit of the operating range (see below), you actually risk a defect, which would then no longer be covered by the liability for material defects."
20 What is behind the bike categories that manufacturers specify for their E-MTBs?
In addition to the recommendation for the permissible total weight, manufacturers also make a recommendation for the appropriate area of use for a wheel. Most, but by no means all manufacturers, follow the application classes of the American Society for Testing and Materials, ASTM for short. These use classes describe the terrain in which a bike should be used. Many E-Enduros are sensibly approved for ASTM class 4, which means that they may be used "on rough terrain up to a maximum speed of 40 km/h". Jumps and drops can occur up to a maximum height of 122 cm." But be careful: some manufacturers have their own categories. Cube, for example, also approves its Stereo Hybrid 160 for "Category 4". However, Cube's categories are not based on the ASTM standard, but are much more restrictive. For category 4, only "sporadic jumps of up to 0.5 metres" are permitted. If you stray outside the range of use recommended by the manufacturer, the liability for material defects will no longer apply and you will have to pay for any damage to the material yourself. Even the product liability expires. So if a defect leads to a major injury, you may even have to bear all or part of the treatment costs yourself - or your own health insurance may have to cover them.
Adrian Kaether
Editor
