Contactor, E Stop button, On/Off toggle switch

Hi everyone! I have been researching and searching for a few weeks now and have not found any reasonable answers that I need.
To my Project:

I am building a Race Kart out of a fairly new Tony Kart shifter Chassis. It will be a purpose built race vehicle, so no need of any lights, horns, turn signals etc.

To my components:

QS 138 90h Motor and a Siaecosys Far driver 96850 controller with 450 Bus Amps. The battery will most likely be a 23s2p with ePlb c020 cells and 84V nominal and ANT smart BMS.

I will be wanting a simple Emergency ON/OFF switch between the battery and Controller in case of an emergency, something like the Albright E Stop buttons and a simple ignition on/off button instead of a key ignition.

My Questions:
Do I have to use a Contactor between the battery and controller? There are a lot of different opinions on this and I just don't know why it would be necessary. The lady I spoke with at Siaecosys said that the far driver didn't need a Precharge, so one thing less at least.

Is it possible to wire in a simple toggle switch instead of the Key Ignition? There is only one wire going to the key ignition so I am guessing I will need a ground wire, possibly from the anti theft?

I will be replacing all plugs for more durable sealed plugs anway so I don't mind if I need to rewire to use a toggle switch. The Reverse switch should work nicely with a normal toggle I presume.

Is there anything else to worry about or to install? A DC converter will not be necessary.

Arming plug rather than a switch

as robust as the plug selected
cheaper than a switch
some contribution to anti theft

not a blueprint but to be adapted

https://www.radicalrc.com/category/Plug-Mount---Arming-Switch-297

Nice kart

I'm surprised that you don't need to pre-charge a 90V controller. It must do it internally.

Thanks, yeah I was surprised as well but I guess they do it internally. I am just not sure about the contactor or rather, what it is exactly for.

When I ran a contractor on my 100V 4 kW bike I felt it was more trouble than it was worth.

Can nobody else help or advise what to do? If almost everyone uses the contractors then I am guessing that almost everyone know what exactly they are for and if they are really necessary with a good controller and BMS.

There is no real need for contactors, but it can be nice to be able to turn off the output from the battery before working on something in the system.
I saw you will use a bms that you can turn off, that will be enough if there aren't any rules that says something else.
The controller might not need the pre charge, but your switch will probably live longer with it.

Why 23s with that controller? 28s would make more sense. Otherwise a 84850 would probably be better.

You can probably use just about anything you like as a "key switch", but it looks like full voltage from the battery is used.
One option is to use a relay that you control with ground, so you dont have to run full voltage up to the steering wheel or were you plan to have your switch.

Btw, sounds really interesting :thumb:
Make a build thread, so we can follow the progress :wink:
The carts build threads are usually here:
https://endless-sphere.com/forums/viewforum.php?f=34

Wimbi39 said:

Is it possible to wire in a simple toggle switch instead of the Key Ignition? There is only one wire going to the key ignition so I am guessing I will need a ground wire, possibly from the anti theft?

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Yes, a simple toggle switch can work. Since you will have no 84v bus or 84v—>12v converter, and I assume no alarm/antitheft, you just need a single wire from battery + to the switch, then to the controller ignition.

Since you have no accessories then you don’t need a ground wire run because the vital connectors (throttle, 3-speed selector switch, reverse, low brake) have their own ground wire already.

If you want to use HIGH BRAKE you still don’t need a ground wire but you need to make sure the peak voltage of your 84v battery is not too high for the controller. They do show the DC/DC converter being used for high brake but i think its for conversions of vehicles with standard 12v system so you can use 12v brake light. But if you don’t use brake lights the LOW BRAKE would be a safer option.

If you want to use either the PARK or CRUISE wires then you will need ground but the ground going to the 3-speed switch or LOW brake can also be used since they all are ON/OFF functions. I would NOT tie anything into any if the 3 throttle wires because you want clean power going to the throttle so the signal going to the controller is clean.

I don't know if the PARK or CRUISE wire can be used for other functions with programming like the Votol can, but at first glance it seems everything is locked on one function, use it or don't use it, lol.

I don’t think you need an external contactor. It will spark when you connect the battery (or close the breaker if you have that), but then everything should be handled gently internally when you flip your ignition toggle switch. On the Votol controller you will see voltage gently sag 0.5v when you turn the key on.

As recommended already, hope you can start a build page in the proper section so we can follow along.

Wow thanks for the replys. I wanted the 96V version so I could( if power is not enough) add more cells to make a 96v pack, I am trying to keep the weight down as much as possible but wanted a little more reserve amps as with a 72v system.
I wont be letting the battery plugged in all the time, I want to try to make a quick swap system to be able to switch Batteries between runs, 15min of runtime will be more than enough, I think my arms will give up after 10min hehe.

Could I use a power wire from the antitheft power supply instead of running a wire from B+?

I unfortunately do not work for a CNC or milling company so I will be fabricating everything myself (except the Motor mounts) I am trying to go as minimalistic as possible, it shouldn't look like a spaceship with 27km of wiring, just a clean and fast Kart.

I will be definitely making a build thread, I will be trying to make time for it in the evenings which isn't always easy ( I have three kids at home due to the virus situation and maintaining their toys and vehicles takes up most of my time anyway :lol: )

Wimbi39 said:

Could I use a power wire from the antitheft power supply instead of running a wire from B+?

Click to expand...

I don’t know if it would work or have any problems. According to the drawing alarm power is 60v, and normally its battery voltage used. But I don’t know if its like high brake where anything between 12v and battery voltage makes it work. I dont know the path of the pre charge current, or if the ignition wire voltage is used for low voltage signal.

In the voltol controller the alarm uses battery voltage and when you use remote start it backfeeds the battery voltage from the controller to your switch (which is still open), thereby powering everything between the switch and the controller. This normally includes the display, and on basic EVs it also powers headlight, turn signals, brake light, horn, which are all designed to run on battery voltage.

What are you planning on using for a display and instrumentation? Just an android device connected to the controller via Bluetooth or a dedicated display, amp meter, and whatever else you want? If you need power for it then that should be planned ahead. You might just need a 10A 5V usb power supply so you can keep your device running well or battery voltage to your display to get the correct voltage indication if not using the app.

Im not sure either if the anti theft runs on battery voltage or anything between. As soon as I get a battery built I will be able to check the voltages on every wire, I just wanted to get everything organized and maybe bought and wired up until then. It won't be easy finding an on/off switch which runs on 80+ Volts.

I was planning on using an Android device showing the telemetry of the BMS, but maybe a Shunt with display devices would be more accurate. I would then have to run the whole current through the shunt which means even more losses and another thing that could cause problems. I use a AIM and HM telemetry on my race bikes with suspension, brake, throttle sensors etc but I think for a kart, Current and battery voltage would be enough information. It would be great if there was a GPS laptimer that could show those values, would definitely be interesting for a lot of other builds as well.

Wimbi39 said:

It won't be easy finding an on/off switch which runs on 80+ Volts.

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I wouldn't worry about the voltage rating unless there’s a light inside. I doubt any of these ebikes have an ignition switch rated at 100vdc. In your application you will only send a tiny bit of current to the controller and instrumentation so any standard quick make/quick break switch will last you 10,000 cycles before any significant pitting occurs.

My $0.50 ignition switch is probably rated for 12v, but i use it on a 60v nominal system which if all posts things are on (headlight, turn signal, tail light, brake light, display, USB 5v power, horn) its still doesn’t arc.

However when i connect my battery to the controller, especially the hardwired ones, that last wire will startle you if you slowly connect it. Lol. But there is a lot of inrush current charging up some capacitors.

My brake levels have tiny sensor switches which also connects 60v to my controller high brake and the led brake light and they take it without issue so far.

You can make a jumper from battery + to your ignition wire and see if any spark and then you will know how pit-resistant your switch contacts need to be.

I have started a build thread here:

https://endless-sphere.com/forums/viewtopic.php?f=34&t=114391&p=1691515#p1691515