How to Calculate the Range of An Electric Bicycle
The range of an electric bike is how far you can ride it on one charge. A common problem is figuring out how to assess electric bike range. All electric bikes are advertised as having a particular range. However, these advertised ranges are often inaccurate. In fact, sometimes they are downright exaggerated, and may even be four times higher than the reality. Here is a guide to help you figure out the true range of an electric bike.
Factors to Consider that Impact E-Bike Range
If you think about it, it is impossible for electric bike range claims to be totally accurate. There are too many factors that make the range different from person to person. These factors include:
· how much the rider weighs (you will get longer range if you weigh 100 pounds than if you weigh 400 pounds);
· what level of assistance the rider chooses;
· the terrain they’re cycling over (you will get less range in the French Alps than you will get in the Sahara Desert);
· the amount of luggage they’re carrying;
· how fast they go (1/3 faster = 1/2 the range);
· how hard they’re pedaling;
· how many times they stop and start (hill starts in particular will drain power);
· wind conditions;
· temperature (they will get about 15% more range from a battery on a warm sunny day than they would in winter);
· tire pressure (as with regular bikes, soft tires = less efficiency = less distance for power expended);
· what kind of battery they’re using;
· how old their battery is (batteries lose power over time);
· size of their bike motor (big motors are fun, but obviously they drain more battery power); and
· how fast they’re going.
For example, if you decide to engage no assistance at all because you’re on flat terrain and you’re feeling strong, your electric bike range is as far as you can go before you collapse. For some people this might be 200 miles, and for others it could be 20. On the other hand, if you engage the highest level of assistance constantly, and are in very hilly terrain, you can eat through your battery charge pretty fast.
And if for example you have a lithium battery, you’re going to keep going a lot longer than if you have a nickel-cadmium battery, as lithium batteries have a higher energy density. See my post on how to choose the right battery type for your electric bike.
Battery Power vs. Motor Power
Bear in mind that your battery size and your electric bike motor have to be well matched in order to get optimal range. As a general rule of thumb, look for a setup in which the battery capacity in watt hrs is equal to the motor capacity in watts. This kind of setup will have the greatest range because the motor will not over-tax the battery. You should be able to get at least one hour at maximum assist with this kind of setup.
As an example, the top-of-the-range had a battery with 355 Watt hrs (36 V/9.6 amp hrs). So the motor capacity and battery capacity in watt hrs were almost identical, and the battery was advertised as having an impressive range of 56 miles (90 km). However, the reality is that you would not be able to travel 56 miles in one hour on most electric bikes (unless you were coming down Mt. Everest).
Bear in mind that many electric bike motors are capped at 20 miles (32 km) per hour. So that 56 miles would be achieved more likely in about three hours, and definitely not using the full assist the whole time – there would be a whole lot of pedaling going on as well!
Battery Capacity is the Most Important Factor
Most people will want to have the most powerful bike motor they can afford. But in fact, motor power only impacts how fast you can pull off, and how well you can get up hills. It does not necessarily impact how far you can go. The most important variable to look at in terms of electric bike range is battery capacity.
The size of the battery is directly analogous to the size of a car’s gas tank.
Battery capacity is usually measured in Watt-hrs. Watt-hrs = amp-hrs x volts (that is, power is equivalent to how long the current will be applied to the battery’s potential, multiplied by the amount of potential power the battery has).
Watt Hrs vs. Amp Hrs
Note: when you are looking at adverts for electric bikes, you may find some where battery capacity is simply stated in amp-hrs. This is insufficient, as it does not include the voltage, so it does not reflect the true energy capacity. So if a bike is advertised with a 36 volt battery, with a capacity of 9 amp hrs, then the true capacity of the battery is 9 x 36, that is, 324 watt hrs (written as 324 Wh).
Watt hrs are important, because watt hrs determine the range of your bike, that is, how far you can go.
For example:
1. Bike A has a 24 Volts and 20 AH battery = 480 watt hours.
2. Bike B has a 48 Volts and 10 AH battery = 480 watt hours.
3. Bike C has a 24 Volts and 6 AH battery = 144 watt hours.
Bikes A and B have a similar amount of energy. If Bike A and Bike B have equal motors and riders, they will perform in a very similar fashion. The bike with the higher voltage battery will accelerate faster and climb better – but that will be at the expense of some of that energy. On the other hand, Bike C will not take you nearly as far.
Bearing all of the above in mind will help you to evaluate manufacturers’ advertisements and claims for their batteries. In general, you want a battery with a minimum of 200 watt-hrs.
Take the time to ask if there is an option to get that same bike with a higher capacity battery. It may very well be worth the extra cost (and the extra time while the dealer puts it together for you).
-Gravity Ebikes
info@gravitysz.com
12th/10/23