Control system for my electric scooter

Projects General Guidance
1

Hi
I have an electric scooter that comes under the Ebike class 15mph max, 250w motor, pedals. This scooter has not been modified as of now, a previous one I did modify. I changed it to 72v LiPo battery pack, new controller, independent ebike cruise control. Although this is for my scooter i want to make it available to anyone that wants to use one.

What I want to do is build a control unit that as the following functions.

1: Stay within a speed limit set from the unit.

2: Be able to mesure speed from either a hall sensor in the motor or a cycle computer wheel sensor.

3: An odometer that can be set from the unit. A trip meter that is reset from the unit not on power up.

4: Be able to mesure both volts and amps, this wil give me watts and with the clock function also mesure watt hours he way most battery packs are measured by.

5: Have a cruise control that uses speed as its controlling factor not throttle voltage that nearly all cruise controllers use.

6: The unit must have as few switches on it as possible.

7: Most controllers have several “speed” power settings on them controlled via a switch, give control of the speed setting to the Arduino with manual override.

8: Distance and power amounts must be stored to EEPROM before complete loss of power, I have an idea on how to achieve that.

9: A small display probably 1602 LCD.

10: A braking system that if you have a DD motor only activates the regenitive braking if the brake that has the motor in it is pulled.

There probably will be other things I will think of as the project progresses.

What I have to work with so far.
72v speed controller with a wire coming out that is attached to one of the hall sensors
For development I will be using a Arduino UNO R3 for the final version I want to use either a Nano or a Pro Mini 5v 16mhz.
72v 20s lipo battery 15ah or 20ah with a BMS attached. The BMS has separate power and charging ports, there is a MCB fitted between the battery and the controller to prevent power drain when the scooter is not used for a period of time.
A heads up display that takes up quite a bit of room on the dashboard, there should be enough room for a 1602 lcd display.
Extra handlebar switches on order to for the controller and Arduino.

Kendrick

2

25W? not 250W? Even that is very small for a 72V system. I would expect to be up at the 1000W level if I'm working with that kind of battery. 24-48V seems more normal for that wattage.

You have a VERY ambitious set of goals there. Can you find even one commercially-available controller which does 75% of that? If you can't, then it means that there aren't a lot of other people out there with similar requirements and you should re-think your ambitions. I think it will be easy to find a pre-built controller that has 50% of those functions, so it may be best to start from there and add individual functions via your Arduino project. Also consider adding other commercial modules, such as a watt-meter/fuel-gauge just as a display.

Even your first requirement is a bit odd. There's probably several good reasons why this is rare. I suspect that all of the scooters which actually attempt to comply with the government speed limits are only tested on level ground. On a downhill, should it try to slow you down or should it still let you use the power available?

The scooter manufacturers are also trying to manufacture devices which work under many different government regulations. The speed limits are different in every country. So it is not really economic for them to design in the speed limit. They just meet the simple wattage restriction and leave it up to the user to control their own speed and pay their own fines. You're custom-making something for your specific situation so maybe it is a good idea for you.

3

Thanks for picking me up on my error I have now edited that it should have been a 250w motor.

At present the scooter uses a 48v battery pack I have not done a check on the power output but I have a feeling that it has been limited so the scooter can go no faster than 15mph or as the speedometer reads 25kmh.

I have read and tested on a previous scooter using the same controller that acceleration and top speed are voltage related on a controller that has plenty of watts available the controller is the same as I will be using on this build.
As I went from a 36v pack through 48v and up to 72v so there was an increase in both acceleration and top speed. Higher than 72v and you have to start changing components to higher rated ones. My last scooter had a 72v 15 ah battery pack and I could get 20miles out of it on a single charge.

There is a device out there that can do most of what I want called a cycle analyst for any dedicated ebiker it is the best device to fit, I have used several myself including on my previous scooter.

The first thing on the list will probably be one of the most hard to achieve smoothly but to keep under the laws radar but keep the power it is my only option I used to do the full throttle from a junction once I get to the speed limit of 15 mph I try to throttle back but invariably miss it and am going at 20mph plus, the law states the motor must get you to a maximum of 15 mph manufactures do this by making the overall power of the bike limited approximately 750w is the amount of power required to get you to 15 mph but the down side is limited acceleration and the time to get to full speed is about 30 seconds if you go down the route I want to go down you will get to 15 mph in less than 10 seconds about the same as a car from a set of traffic lights.

Going at 19mph will probably not cause any problems with the law but going at 30 and staying up with the traffic in town will. At 19 you can say the manufacture has not done a good job at limiting the power.

Kendrick

4

First thing to do was to to see what output I was getting from the hall sensor From the wheel through the speed controller using a multimeter.

Results of first test, the voltage at maximum is 5v.

Now I have to build a shield for the uno big enough that I have access to all the pins and it has a built in display to see what the results I am getting are.
Kendrick