An ebike electric motor is silent and discrete, although sometimes it purrs when delivering its mellow, yet generous power. A loyal companion for daily commuting, venturing into the wild, enjoying fascinating journeys. Astoundingly reliable and durable, if you give it good care and some little maintenance.
Electric motors in general are more reliable, robust and durable than thermic motors (ICE). That’s true for ebike motors as well. Nevertheless, they can be prone to wear and damage because of their functioning, in combination with pedaling, and even more their exposure to rain. Electric motors of cars, for instance, are much better protected. Some advice to prolong their lifespan.
Electric ebike motors premature wear and failure: causes and remedies
Normally, ebike motors should last, on average, 20,000 miles or 32,000 km. Yet they can need repair or even replacement much earlier, depending on usage conditions, especially if they are not well cared for.
Water ingress due to rain or riding on wet terrains
Any amount of water, no matter how small, that penetrates the electric motor, corrodes internal components, damages wiring, bearings, windings and magnets. Riding on wet roads and terrains exposes your motor to water spraying. Mid motors are much more subject to water damage than hub motors. The former are literally hit by rain, should your ebike have no front fender or a short one, or water on the road or trail. The latter are enclosed, thus normally much more water resistant, although not quite waterproof. E-mountain bikes motors are often protected by a motor cover. Submersion should be avoided in any case. Just look at the picture below: rust has wreaked havoc on this poor, although high-quality motor.
Moisture
Moisture should be avoided, because it can be as damaging as water. Even in absence of rain and water, moisture can affect the above-mentioned motor components because of external environmental influences. Storing your ebike in a humid cave or garage, or outside, even if a roof is sheltering it, will let moisture penetrate your motor. Should you protect it with an ebike cover, beware of condensation. It can let moisture accumulate under the cover and damage your motor.
Decently long Fahrer ebike mudflap.
Protecting your motor against moisture and water
Water and splashing coming from the front wheel onto the mid motor: whenever you ride on a wet terrain, just verify if your motor or motor cover is wet. That would mean that your front fender is, as usual, too short. I strongly suggest you get a mudflap. Its lower edge should be at least 5 cm lower than the bottom of your motor, otherwisethe airflow will splash it.
If rain catches you by surprise while riding, and you can’t stop, why not keep a plastic, thin shopping bag folded under your saddle, in order to wrap it around your motor and tie it by its handles in case of sudden rain?
Sheltering your ebike in a garage or in any building is essential.
What to do in case your ebike motor got soaked or really wet
Water can act as a bridge, creating connections between electrical parts, which result in short circuits. If your ebike, control unit, display, cables or motor are really wet, just switch your ebike off, or don’t switch it on, and store it a not too warm (to avoid condensation), dry place until it’s really dry.
Rusted motor gears – water got in.
Overloading should be avoided
Quality ebikes normally specify the maximum load, which is usually around 130 kg, or 280 pounds, including the rider. Be careful: that is their weight not to be exceeded in order to avoid damaging rims, spokes and the cycling parts. Should you ride a long distance on a steep incline carrying maximum or nearly maximum prescribed load, your motor could considerably wear off or even be seriously damaged if not broken. Often pushing a motor beyond its limits can all but assure its premature failure. If you have twisted your motor to get electric support up to 45 km/h and more, just consider that you will stress it to a level that it was not conceived for. Premature wearing is then sure, failure possible.
Operating the motor above its rated capacity generates too much heat, exceeding the allowable temperature rise. Beware of long steep inclines and of carrying heavy loads.
Insufficient maintenance
Omitting to periodically (every 5,000 to 10,000 miles) clean and grease your motor gear will accelerate its wearing and shorten its lifespan. Besides that, your motor works in combination with your legs and your ebike transmission. The more power your pedals deliver to the wheel, the less will be demanded by the motor. The more your whole transmission is well maintained for optimal performance, the longer your motor will last. That’s why even details like flat tires or loose and dirty chain, or worn off gears, requiring an additional effort for your motor, are detrimental, because they burden your motor with extra efforts.
Excessive heat
Electric motors are classified according to their insulation system’s temperature rating. This rating indicates the maximum operating temperature the motor’s insulation can withstand continuously without significant degradation.
Following their approximate maximum operating temperatures, these classes are:
- Class A: 105°C (221°F) – This is generally considered the lowest temperature class and uses cotton, silk, or paper as insulation materials. These motors are typically less expensive but have a shorter lifespan compared to higher-temperature classes. Uncommon in modern applications.
- Class B: 130°C (266°F) – This class uses mica, glass fiber, or other inorganic materials, offering improved heat resistance compared to Class A. It is a common class for many industrial and general-purpose motors, and ebike motors generally belong to this class.
- Class F: 155°C (311°F) – Class F insulation uses materials like mica, glass fiber, and synthetic resins, providing better thermal stability than Class B. It’s suitable for demanding applications with higher temperatures or increased loads. Some ebike motors belong to this class
- Class H: 180°C (356°F) – This class utilizes silicone-based materials, providing the highest level of thermal stability among commonly used insulation classes. These motors are suitable for very high-temperature applications and are often found in specialized industrial settings.
- Class C: >180°C (>356°F) – This class denotes insulation materials with exceptional high-temperature tolerance, such as ceramic materials. Applications are extremely specialized.
In the end, ebike motors don’t become very hot. Reckon that internal combustion engines easily reach at least 900°C, or 1652 F°. Still, since they often contain plastic gears and sometimes belts (e.g. some Brose motors), high temperatures can prematurely wear ebike motors and even cause them to fail. If you suspect that your motor is exceeding the above-mentioned maximum operating temperatures, just touch it with your hand. Internal temperature are at least twice as high as what you touch. So you shouldn’t scald you if the motor is not too hot.
Ambient Temperature: the maximum operating temperature of the motor is a rise above the ambient temperature. If the ambient temperature is high, the motor’s actual operating temperature will be higher, potentially exceeding the insulation class limit. Especially in this case, riding for at least a couple of minutes at a speed beyond your motor assistance limit is a good way to cool it off.
Poor ventilation increases the motor’s temperature, potentially leading to overheating and insulation damage. Some motors have fins. On the other hand, some e-mountain bike motors are well protected against the dirt and dust, what can limit or even exclude ventilation, despite some aerating holes, see image below.
Motor cover
Mechanical problems that can negatively affect ebike motors
Bearing Failure: This is a common cause of motor failure. Wear, lubrication issues (lack of, incorrect type, or contamination), improper alignment, and excessive vibration all contribute to bearing damage. Symptoms include noise (growling, rumbling), increased vibration, and eventually seizing.
Shaft Misalignment: Improper alignment between the motor shaft and the driven equipment leads to excessive stress on bearings and other components, causing premature wear and failure.
Winding Insulation Degradation: Over time, motor windings can degrade due to heat, moisture, vibration, and chemical exposure. This leads to reduced efficiency, increased resistance, and ultimately, short circuits or open circuits.
Rotor Issues: Problems with the rotor, such as imbalance, broken rotor bars (in induction motors), or damage to the rotor windings (in synchronous motors), can cause significant vibration and failure.
Mechanical Overload: Exceeding the motor’s rated torque capacity leads to excessive stress on various components, including bearings, shafts, and windings.
Loose Connections: Poorly tightened connections can lead to overheating and eventual failure. This includes terminal connections and internal connections within the motor itself.
Electrical problems
Stator Winding Faults: These include short circuits between windings, open circuits, and ground faults. These often result from insulation breakdown due to overheating or moisture.
Rotor Winding Faults (in AC motors): Similar to stator winding faults, these can result from insulation breakdown, often due to centrifugal forces.
Overcurrent: Excessive current flow due to overload, short circuits, or other electrical faults can cause overheating and damage to windings and other components.
Voltage Imbalance: Unequal voltages on the three phases of a three-phase motor can lead to overheating and premature failure.
Power Supply Problems: Issues with the power supply, such as voltage fluctuations, surges, or harmonics, can stress the motor and lead to failure.
Images: Bosch, E-Bike Motor Repairs