## How do I extend my electric motorbike's battery range?

### The slower you go, the further you'll go.

I'm going to explain a bit about how range is calculated using the example of the 6-series motorcycle to help you understand what influences it. First, if we think about motor power, the 6-series has a motor that's rated at 5kW continuous and 8kW peak. Peak power is the amount of power it can put out for a short amount of time and continuous is the normal cruising power. What does this mean for the 6-series? How much power does it need to reach a cruising speed of say 70km/h? The amswer is basic physics based mainly on the aoerodynamic drag, road friction, the slope of the road and the wind. Check out the power vs velocity graph that I calculated. It's exponential thanks to the aerodynamic drag.

This graph applies the same to petrol bikes. For example a Honda MSX125 has a top speed of 90km/h and peak power of 7.2kW.

The 6-series has a stated range of 150km. What does this mean?

Well, using the power graph, we can work out the range. For example, if we are cruising at 50km/h, we are using about 1.3kW. The maximum battery capacity is 7.2kWh, so we could travel about 5.5 hours at this speed and travel 276km.

Another example, this time cruising at 90km/h we're using 7kW of power. This means we'd use the battery up in an hour and go only 90km. If you carry on this way, you'll end up with a graph like the one below showing that it's better to go slooooow.

The actual range isn't one number, it's between 50km and 250km. The stated range of 150km is an average of these figures.

Some things to notice about these calculations. First, you won't run down the battery to 0%, which means the usable range will obviously be lower. Secondly, the bike itself has power losses from the motor and controller that again will reduce the range. The broader blue line in the graph shows an area of possibility between what we assume are the best and worst case scenarios.

The conclusion is that range isn't one figure and in fact varies massively depending on your speed. You're not going to go slow on an electric motorbike so bear this in mind.

##### Ian Former

Expert consultant at Devs motorbikes, media junkie, sports fan. I spend a bit of my time thinking about what we'll do when the oil runs out.