Tapping onto a 36V d.c. Battery on eScooter with Arduino

Thread Starter

cxshermansg

Joined Sep 1, 2017
10
(I apologise in advance if I might have posted this in the wrong forum group)

Hi guys, I have done a bunch of research lately on the possibility of tapping my Arduino prototyping project onto an e-Scooter which runs on a 36V d.c battery source. I have so far managed to identify 2 possible components that makes it possible:

  • d.c. step down (for stepping down the voltage to 3.3V~5V) - for channeling the current to my arduino boards and sensors.
  • Relays (I have ordered a few relays online which comes quite cheap. I read and viewed tutorials about how relays can be used to power devices with a higher current/voltage. With the relay work for this case?
I am pretty sure many of you here are probably more experienced or experts in the electrical and electronics engineering field. I'm from the computing background, but I do have some background knowledge in electrical engineering & electronics (introductory materials and crash course stuff). Can someone help point me in the right direction? Or if you think there is some resources or technical knowledge I should read up on as well, I would appreciate it if you can let me know.

P.S. I am also hoping to tap into the speedometer, brakes, the basic functions of almost all e-scooters in general.
 

Dodgydave

Joined Jun 22, 2012
9,090
Post a link to the DC buck converter you want to use, as long as it can give the required output current for your design it should be ok,.

As for relays, they can be driven from the battery directly via a pass transistor using a 24/36 V coil, or use a 5V coil and feed them from the buck psu.
 

Thread Starter

cxshermansg

Joined Sep 1, 2017
10
Post a link to the DC buck converter you want to use, as long as it can give the required output current for your design it should be ok,.

As for relays, they can be driven from the battery directly via a pass transistor using a 24/36 V coil, or use a 5V coil and feed them from the buck psu.
@Dodgydave: Thanks for the explanation. However, I have to be honest that I still don't quite get it. Sorry if I sound like a noob when it comes to some of the electronics & electrical explanations.
 

Reloadron

Joined Jan 15, 2015
5,363
A few considerations. There is no shortage of DC to DC converters available from a variety of manufacturers and sources out there. Things you need to consider is for example an Arduino can easily be externally DC powered with 7 to 12 volts DC. So let's say you choose a 12 VDC option. You will be reading inputs from several sensors using your Arduino. Each Arduino board will draw a varying current depending on how much work it is doing. The Arduino itself can drive several relays through using a transistor to drive the relay coils. Each relay coil will draw some current, so we have more current draw. A word to the wise here is relay coils are an inductive load and unless driven correctly can create headaches for the Arduino or any micro-controller used to drive them. Frequently an opto-coupler is used to drive relay coils when we employ a micro-controller. More on all of this later.

Your first concern is to estimate the maximum current you will need with the DC to DC converter output. For example I can drop the 36 volts of the golf cart system to let's say 12 Volts and feed all my Arduino boards and relay coils but I need to know how much current my DC to DC converter will need to deliver. Do I need a high current available like this unit can provide,Golf Cart Voltage Reducers - 36/48 Volt to 12 Volt Converters - 20 Amps, or can I get along with a much smaller current like uxcell Waterproof DC 36V (30V-50V) to DC 12V 10A 120W as an example. Maybe your needs are only a few amps meaning an even smaller unit would do just fine. Your actual relays themselves need to be chosen to handle the load currents they will be switching. That becomes another consideration in exactly what you are wanting to accomplish. This Arduino Relay Tutorial gives a good overview of using relays with an Arduino.

Thanks for the explanation. However, I have to be honest that I still don't quite get it. Sorry if I sound like a noob when it comes to some of the electronics & electrical explanations.
No problem at all, just explain what you do not understand. Anyone here will be happy to help you understand. It's just a learning curve. :)

Ron


 

Plamen

Joined Mar 29, 2015
101
Apart of relays, MOSFETs can do the switching in most cases...even the traction motor. Relays consume a lot, have inductive kick, are sensitive to vibrations, are not exactly cheap, have limited life...
 

Thread Starter

cxshermansg

Joined Sep 1, 2017
10


Hey, guys, I'm back with an update from my project. So I've managed to tear down my entire scooter today until I only kept aside what is necessary for the prototype. I have managed to identify some of the key parts including the 2 charging nodes from the e-scooter which plugs into the 36V DC battery. It's a Li battery.

On the tiny board attached to the contact points (see below), I have identified the +36V node as well as the GND. It doesn't mention anywhere that there is a -ve. So do I assume that the GND is the -ve?

(internal view)


(external view)

Additional info: From the battery pack, which I opened up to take a look earlier, it shows that the red wire is going to the +36V node and the black wire is going to the GND node.

Can someone help me to look at the diagram I have drawn and let me know if there are any potential challenges or problems I might face on this project? I only have one chance to get it right so I want to make sure I have covered enough bases to make sure I don't connect the wire the wrong way and fry my project to kingdom come.
 

dendad

Joined Feb 20, 2016
3,431
Yes, I would say the "gnd" is the battery -Ve connection.
What are you actually trying to do?
Is it a going scooter that you just want to add extra stuff to and use its 36V battery?
Or are you making a new controller?
And when you say "scooter", what do you mean? A toy scooter or a mobility scooter?
Often on this forum, people want help but do not supply full info.

As for powering the Arduino off the 36V, you will need to get a buck converter that can handle fairly high input volts.
I use quite a lot of these...
https://www.recom-power.com/pdf/Innoline/R-78HBxx-0.5_L.pdf
Their max i/p is 72V so there is a fair bit of headroom. A 36V battery can go over 40V, not counting transients.
make sure you have a bit of headroom to save letting the magic smoke out.

And relays don't power anything, they are just switches. You can switch the 36V with one, and have the relay with a 5V coil so it runs of the Arduino 5V, or a higher voltage coil and run it of the 36V. But I think 36V coils will b hard to find, so use 5V relay coils switched by a transistor driven by the Arduino. The Arduino cannot drive a relay directly as the ports have a limited current capability.

I think you need to have a play with a lower powered project first.
Try the Arduino running a small motor and getting control of that before you branch out to bigger things.
 
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Thread Starter

cxshermansg

Joined Sep 1, 2017
10
Yes, I would say the "gnd" is the battery -Ve connection.
What are you actually trying to do?
Is it a going scooter that you just want to add extra stuff to and use its 36V battery?
Or are you making a new controller?
And when you say "scooter", what do you mean? A toy scooter or a mobility scooter?
Often on this forum, people want help but do not supply full info.

As for powering the Arduino off the 36V, you will need to get a buck converter that can handle fairly high input volts.
I use quite a lot of these...
https://www.recom-power.com/pdf/Innoline/R-78HBxx-0.5_L.pdf
Their max i/p is 72V so there is a fair bit of headroom. A 36V battery can go over 40V, not counting transients.
make sure you have a bit of headroom to save letting the magic smoke out.

And relays don't power anything, they are just switches. You can switch the 36V with one, and have the relay with a 5V coil so it runs of the Arduino 5V, or a higher voltage coil and run it of the 36V. But I think 36V coils will b hard to find, so use 5V relay coils switched by a transistor driven by the Arduino. The Arduino cannot drive a relay directly as the ports have a limited current capability.

I think you need to have a play with a lower powered project first.
Try the Arduino running a small motor and getting control of that before you branch out to bigger things.
Hi, I'm sorry if I haven't provided sufficient details. So here are some of my replies:

1. It is a 2-wheeled mobility scooter.

2. For the purpose of my prototype, there are ideally 2 stages (since I am not a pro):

a. Be able to channel the power from the 36V d.c. battery to my arduino board which I will be able to demonstrate the ability to switch on/off the power to the rest of the mobility scooter using a program written for Arduino (e.g. the scooter has traveled a particular distance/the battery usage has reach a certain percentage, or when a user just paired with the ride to start using it, it will turn on the scooter). I have a LM2596S DC to DC Buck Converter for stepping down the voltage. The product description says that it has an input voltage range of 4~40V. Would this work? Or do I have to get something else?

b. Ultimately, the main reason of integrating the Arduino board is so that I can use it as the bridge between the d.c. battery as well as the brake system, touch screen display, and in future, adding other custom sensors/components.

3. Existing Components:


(Above Image) This image shows the existing controller which is connected to the brake and accelerator. On the underside of that is actually the display screen which shows the battery level as well as speedometer.

Project Goal: My goal ultimately would involve reverse engineering this and putting it into my Arduino project. My touch screen LCD display will be able to show the speed as well as battery level (current goal) plus providing a menu option for accessing other things (in the future).


(Above Image) I am not an electronics pro, so if I described anything wrongly, please pardon me. what you see above is the controller which acts as the bridge between the display + brakes + accelerator + motor and the battery source. I was guessing that the microcontroller you see in the picture contains a program of sorts.

Project Goal: To create that custom bridge as I have just mentioned. I am currently also trying to research on how I can reverse engineer it so that I can build my own set using Arduino.
 

dendad

Joined Feb 20, 2016
3,431
You have a pretty big project on your hands there.
For the regulator, I would go for a greater input voltage allowance myself. In this case, overkill is better.
As mentioned before, these have a 72V input.
http://au.rs-online.com/web/p/switching-regulators/6727095/
You can get them from mouser.com too Mouser # 919-R-78HB5.0-0.5L
Motors will generate voltage spikes so the power supply has to be pretty tough. Add a Tranzorb to the input too as that will chop off any big spikes, and make the input filter capacitors higher voltage too. 63V versions will be fine.
Are you going to do battery charging /discharging protection too? That is pretty important in the interest of preventing fires!
 
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