I ride an electric scooter as my primary method of getting around. I have a question regarding power usage and battery life. I’m hoping that the engineering types here can help me out.
Battery life is shown as a display of 4 bars, with 4 being full or nearly so and 1 being empty or nearly so. I have observed that on occasions when I am pushing the distance, there is a range between 2 and 3 bars where if I have the throttle pegged, the display shows 2 bars but if I back off some, the display will go up to 3 bars again. This condition will hold for a fair distance. I then experience the same phenomenon between 2 bars and 1.
I interpret this as that the display is showing an estimated distance that can be traveled at the current rate of battery consumption. So, my question is whether there is a difference in the actual distance that I can travel if I back off from maximum throttle, or will the distance be effectively the same with the time elapsed being greater or lesser? I hope I have made the question clear.
I’m putting this in Factual Questions since I hope there is a factual answer. If there isn’t and it becomes a matter of opinions, please feel free to move it to the appropriate category.
Two parts to the answer.
Very hard to really know what something as simple as a four bar display is actually trying to convey. Much depends upon the sophistication of the whole system, and how much effort the manufacturer put in.
The state of charge of the battery can be estimated by a whole range of things. The voltage of the battery is a useful surrogate, but this depends upon the battery chemistry, design, and wear. It becomes less useful when the battery is under load, as the voltage will drop under load. So a simple system will show a lower state of charge when the load increases, which would match your experience. Doesn’t mean the system is this simple however. Modern battery systems are not this dumb, but it provides a baseline. A couple of decades ago this is what you might expect.
A much more sophisticated and nowadays common system will monitor the battery voltage, input charge current, output current, and estimate the remaining charge, and host more. Such monitoring can estimate battery health as well. That could indeed provide a state of charge indication that reflects current use as well as charge. Typically they monitor individual cells in the battery, and communicate with the host controller for the device (scooter) with real time state of the battery, and will also engage in charge control. Something like the ST Micro 19983 controller chip. These include eScooters as a use case. A car might use a string of them to monitor the entire car battery. I would be surprised if the scooter didn’t use one of these ubiquitous chips.
Whether the scooter controller bothers to do much more than report a state of charge is hard to say.
As to the actual distance possible, that will indeed drop if you peg the throttle. Battery efficiency tends to fall off when they are loaded higher, and other losses in the whole system increase faster than your increase in speed.
But I suspect what you see is a rough estimate of charge remaining based in part on the actual current drawn. I doubt it is explicitly estimating distance.
Thank you for the detailed answer. It is helpful to know that I will get more distance at a lesser speed. That’s exactly what I wanted to know.
Keep in mind that wind resistance increases by the square of the speed increase.
Double the speed, quadruple the wind resistance.
My scooter maxes out at 13 mph. At that speed I doubt that wind resistance is much of a factor.
I bike at around 15 MPH, and that’s definitely fast enough that wind resistance is the dominant factor.
What’s probably the next biggest resistive force is rolling friction, which might be higher than for a bicycle, but that also increases with speed (though not as quickly: It’s only proportional to speed, not to speed squared).
Only bearing friction (mostly) doesn’t depend on speed, and that should be extremely small in any well-engineered machine.