October 01, 2018
The purpose of an electric scooter (or escooter) is to get you from place to place. Naturally, how far the scooter can go is an important feature. However, the range is often the feature most often complained by riders less to be than advertised. Why is that consistently so?
The range of electric scooters is affected by more external factors than any other performance feature.
The short answer is that the stated range of an escooter is usually the range achievable in IDEAL conditions. This is not a ploy to over-market or short-change the scooter buyer. The manufacturer has to control the conditions for range testing and specify them in order to publish range information that is meaningful.
A responsible manufacturer will clearly state the conditions and circumstances which result in the range they specify. A good example is the recently released Inmotion V10 electric unicycle (EUC). The published range of the V10 is “~70km”. The manufacturer is even careful enough to use the “~” symbol to indicate that this is an approximation. This range is said to be achievable under these conditions:
They have even gone as far as to declare in advance that “riding habit, environment, temp, road condition, load and other factors will affect the range”. This careful and clear treatment of range may have something to do with the intense competition between EUC manufacturers at the time this article is being written. EUC makers are launching a number of new high-end machines at this time and are vying for attention from riders who care very much about performance.
Many electric scooter manufacturers spare the consumer such details, and simply publish a single figure for the range. This can lead to customer dissatisfaction when customers take the range at face value.
In this article, we will show you how battery range can be calculated, and more importantly, what factors suck the life out of your battery, so you can avoid them and maximize your range.
The battery capacity of your scooter is analogous to the size of the fuel tank in a car. The more fuel you can carry, the longer the drive you can get. The motor will be like the engine displacement of a car: the larger it is, the more powerful but power-hungry it will be.
With some basic arithmetic and high school physics, we can calculate the theoretical range based on the specifications of the battery and motor.
Above: It is possible to calculate the range once we know the scooter specifications like battery capacity and motor power.
Let’s say we want to calculate the range of a typical medium-sized electric scooter with these specifications:
The first formula is something we all know:
DISTANCE (Km) = SPEED (Km/hr) x TIME (hr)
This formula says that if we know the speed we ride at, (let’s assume we ride at a consistent speed,) and the duration the scooter can sustain this speed until the battery runs out, we can calculate the distance it can travel.
For the SPEED, we will use the highest possible speed at which we can ride the escooter. The speed limit for Personal Mobility Devices (PMD) in Singapore, where this article is written, is 25km/hr. So let’s use this figure for speed.
For TIME, we can calculate it from the battery capacity and motor power.
To do this, we need to figure out the battery capacity. This is measured in Watt-hour (Wh), the energy (in Watts) it can deliver in one hour.
Watt-hour (Wh) = Ampere-Hour (Ah) x Voltage (V)
So the capacity of our battery is 10.5Ah x 36V = 378Wh
Knowing the amount of energy in the battery, and knowing the power (and hence consumption) of the motor, we can now calculate how long it will take for our motor to burn through this energy:
TIME (hr) = Battery capacity / Power consumption = 378Wh / 250W = 1.512 hr
Now we have the SPEED and TIME to put into our first formula:
DISTANCE = SPEED x TIME = 25 Km/hr x 1.512hr = 37.8 km.
So in theory and on paper, your scooter can carry you for 37.8 km before its battery is fully depleted.
* Note: some manufacturers indicate peak power instead of nominal (average) power. If both figures are indicated, use nominal power for a conservative calculation.
Above: understanding your escooter’s range and knowing what affects it reduces the chances of you running out of battery and getting stranded.
In practice, however, the range story doesn’t end here. Because the calculation so far has only considered the characteristics of the battery and motor. We have not taken into consideration the rider, riding conditions and other factors in the calculations.
Let’s find out in detail the factors that have a negative effect on range, and what you can do about them to squeeze the maximum mileage out of your e-scooter.
Broadly speaking, these conditions or actions compromise range:
Let’s look into each one in detail.
Above: lightweight escooters like the Inokim Mini work best with lightweight riders.
It is common sense that an electric scooter will have to work harder to move a heavier rider compared to a lighter one.
All electric scooters have an indication for the maximum safe payload. Most are rated at 100 Kg, with some larger models at 120 Kg. Some high end or heavy duty models carry as much as 150 kg. The maximum load is not the same as the optimum load. It’s a common practice for electric scooters makers in the market today to use a rider weight load of about 75 Kg for performance tests. This is understandable because 75 Kg is roughly the weight of an average healthy adult male.
In other words, most of the time, any rider heavier than 75 Kg can immediately expect the range achievable to be lower than the published figure.
Problems with overloading tend to happen when large riders buy lightweight scooters for the sake of portability.
Understandably, some riders using electric scooters for first-mile and last-mile commute need to bring their escooters onto trains or buses. This is a good reason to choose lightweight electric scooters like the Inokim Mini or the Zero 2.0.
These scooters may be underpowered for the big riders, but it is alright if the rider understands there is a trade-off and is willing to give up some range for portability.
Above: choosing an electric scooter with a motor power that matches your weight and body size is a practical starting point to make sure you get the best range.
When purchasing a scooter, where possible, select an escooter with a motor power that matches your body size and weight. This is especially important if you are a large person.
Where practicable, heavy riders should choose motor powers of 350W to 500W or more like the Inokim Quick 3, Imax S1 + or other powerful models so the scooter is not constantly performing under strain.
During purchase, the electric scooter salesperson can give you some insights on range versus scooter motor power. Filter the salesperson’s opinions to control for sales-commission motivations and you will have a sense of which scooter power is suitable for you. If there are hills on your route, it usually pays to favour a higher powered scooter (see “Riding uphill” later in this article).
For the scooter itself, shed weight by removing unnecessary accessories and attachments like bags, bottle holders and such to lighten the load on the scooter. Some countries may even have regulations that limit the weight of an electric personal mobility device.
It is well-known in both the cycling and automobile community that under-inflated tyres result in reduced fuel economy. Without going into complicated physics or mathematics, the simple but factual explanation is that under-pressurized wheels deforms the wheel from its optimal shape. This results in, among other things, increased contact surface between the wheel and the ground. Generally, more contact area means more friction.
There have been no scientific studies done specifically for electric scooter tyre pressure performance. But research for automobiles shows a clear correlation between rolling resistance and tyre pressure. The closer the tyre pressure is to the pressure intended by the manufacturer, the lower the rolling resistance. A reduction of rolling efficiency happens when the tyres are even marginally lower than the optimum prescribed pressure.
It is important to emphasize that avoiding insufficient pressure is not the same as encouraging over-pressurizing the tyres, which has its own set of problems. The important thing to do is to maintain the correct pressure as indicated by the scooter/tyre manufacturer. This pressure is usually indicated in the user’s manual. The pressure indicated on the tyre itself is usually the maximum pressure, not optimum pressure.
Above: Bicycle pump with pressure gauge. Extremely useful and importatnt to maintain optimal tyre pressure.
If you don’t yet own one, get your hands on a tyre pump with a pressure gauge. This is indispensable. You can check the tyre pressure and pump up the tyre with a single device. Make it a point to check the tyre pressure every fortnight and inflate if it falls below the optimum pressure. Maintaining sufficient pressure has the bonus effect of reducing the chancesof getting a flat tire, and increasing the tyre’s useful lifespan.
Above: The Segway ES2 is indicated to be able to go ‘up to’ 15 miles (24 Km) depending on ‘riding style and terrain’.
Gradient has a massive impact on electric scooter range. If you ride a bicycle, you will know from experience that riding uphill, even when the slope is quite gentle, takes much more effort than riding on level ground.
Without going into complicated calculations, it is enough to say that any uphill climbs on your route will shave a significant chunk off the range indicated on your scooter manual. Given that scooter-range is calculated on perfectly flat ground but your actual route is not, you are unlikely to ever match the scooter’s published range.
To put things in context, many riders buy an electric scooter to spare them the effort of climbing difficult slopes on foot or on a bicycle. So the loss of range because of a slope is probably a fair trade-off for the effort saved.
If possible and necessary, choose a longer route that goes around the slope. Unless the detour is unnecessarily long, you will usually still end up positive on the range.
Physics tells us that an object at rest tends to stay at rest and an object in motion tends to stay in motion. It takes energy to get a stationary object to move, to increase its speed or to slow it down.
The general energy consumption associated with the type of scooter activity, (from lowest to highest) is listed here:
For electric scooters that use an electronic brake (as opposed to a bicycle-style physical brake), battery power is also consumed when braking because the scooter brakes by the using the motor to resist motion.
In short, the more often and intensely you accelerate or decelerate during your ride, the shorter your range will be.
Above: with a patient riding style, even a tiny seated escooter like the DYU Supreme can achieve an impressive range of 60 Km, a range more commonly found on much larger machines.
When it comes to range, patience is a virtue. Reach your cruising speed by accelerating gently without haste. Maintain as constant a speed for as long as possible. The optimum speed is usually the highest speed which can be sustained by the motor without it sounding like it is struggling. There’s a reason why this is called a “cruising” speed. It should be a comfortable speed and certainly not the maximum speed.
If you are riding an escooter with electronic brakes, where possible, coast to a stop rather than braking hard. By riding this way, not only will you gain more kilometres, it will be a safer ride as well. As a bonus Your tyre and brake pads will also have a longer lifespan.
We can’t control the temperature we ride in. But it is useful to know what temperatures are best for your scooter. The main concern here is the health of the battery, which is directly related to range.
The optimum operating temperature of batteries is similar to what is comfortable for people. Battery manufacturers usually point to 20 ℃ or slightly lower as the optimum operating temperature, and with 20 ℃ to 30 ℃ as an acceptable operating range.
Above: It is tempting to keep your escooter in the car boot for convenience. But this can expose the battery to unhealthy high temperatures on warm days.
This temperature offers the best battery capacity (which means it can be charged and discharged more completely and easily) and is best for the lifespan of the battery in terms of total charge cycles (cycle life). At temperatures higher or lower than this range, both capacity and lifespan start to suffer penalties. As the battery capacity drops, so too does your range.
As far as temperature is concerned, think of your escooter as a living creature, sensitive to warmth and cold just like you. Avoid storing your escooter in the boot of the car under the hot summer sun, or leave it parked for long periods in direct sunlight. For storage, a cool dry place that is indoors and out of the elements and protected from winter temperature will protect the scooter. It is comfortable when you are comfortable.
Unless you are the kind of rider who rides a scooter to death and buys a new one every year, being mindful of the factors that hurt the range of your escooter will help you can get the best mileage and a longer lifespan from your ride. And because the battery is the most expensive component in your scooter, you will be saving money too.
It is also important to understand that electric scooter batteries have a limited number of charge cycles (cycle life). This is generally about 500-600 accumulated charge cycles. Their capacity to hold charge degrades gradually over time. So for regular riders, it may be hard to avoid a battery replacement after a period of intense use. When the time comes, pat your scooter for a job well done and accept the need to revitalise it with a brand new battery or retire it completely.
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