Run / Tow switch - Wire an LED to it like this ?

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Considering an LED for my Run / Tow switch.

I'll be moving the switch up to the dash, and the new switch has an integral LED that I want to light when the switch is "ON".

The LED in the switch has it's own terminals, but I'd need to piggyback the positive (or negative) for the LED power (5v) through the Run / Tow, as the attached diagram shows. Would this pose any issue to the controller / cart ?

I'm assuming that the Run / Tow is in "Run" if the wires are connected, and in "Tow" if the circuit is broken, but haven't put a meter on the switch yet - it could be the other way around I guess, but my question would still be the same.

Thanks for any insight, and if this could cause an issue of some kind.

[Sergio]

That would work only if you have an isolated 5v POL dc-dc converter and keep the negatives apart.

Other options are to use a 48v relay so you only need to run low current wires to the dash and place the led inline with the relay coil or use a 10k x 1 watt resistor to limit the LED current.

I would suggest to connect the LED power source to the key switch so it only turns ON if both the Tow/Run is ON and the Key switch is also ON.

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Originally Posted by Sergio

That would work only if you have an isolated 5v POL dc-dc converter and keep the negatives apart.

Other options are to use a 48v relay so you only need to run low current wires to the dash and place the led inline with the relay coil or use a 10k x 1 watt resistor to limit the LED current.

I would suggest to connect the LED power source to the key switch so it only turns ON if both the Tow/Run is ON and the Key switch is also ON.

Thank you.

Not sure I understand what you mean by POL? I was thinking of using one of those small external cylindrical phone batteries that charges via USB and and has a 5v output. The LED draws essentially nothing and the battery would run it forever, but charge when the keyswitch was on via the main DC-DC running into a 12V-5V converter into the battery charge port. That keeps everything off when the Run / Tow is OFF.

Would that work and not be harmful to the cart wiring as diagramed?

The easy way for sure is to connect it to the DC-DC converter already on board (12v, but LED is 12v anyway but plenty bright with 5v), but it only works when the key is ON and I want to be able to see at a glance the Run / Tow status. The key will usually be off in the garage, so it would be hard to tell if the Run / Tow was on since the light would be out.

If I end up doing it that way, can I still switch the LED as diagramed (but using the cart's main DC-DC converter as the power source instead of a 5v battery)?

[Sergio]

The acronym POL (Point of Load) describes the type of small dc-dc converters used for low power applications, typically less than 5 watts.

What you suggest would work as long as You don't plug the battery to charge or the LED, and possibly the charger, would get damaged.

Unless you use an isolated power source, your 5v LED will be in parallel with the pack voltage since all negatives are common in most 48->12 (nominal) DC-DC converters.

A 2,000mAh battery would last about two weeks powering the led, so depending on the size of the battery manually charging the battery would be time consuming.

It seems like a lot of devices and wiring just to keep an led on, perhaps You should just use a resistor if the plan is to put it on TOW often, or get a small 48v->5v POL isolated converter for around $10 to power the led:

https://www.mouser.com/ProductDetail...fj%2Fmwg%3D%3D

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Originally Posted by Sergio

The acronym POL (Point of Load) describes the type of small dc-dc converters used for low power applications, typically less than 5 watts.

What you suggest would work as long as You don't plug the battery to charge or the LED, and possibly the charger, would get damaged.

Unless you use an isolated power source, your 5v LED will be in parallel with the pack voltage since all negatives are common in most 48->12 (nominal) DC-DC converters.

A 2,000mAh battery would last about two weeks powering the led, so depending on the size of the battery manually charging the battery would be time consuming.

It seems like a lot of devices and wiring just to keep an led on, perhaps You should just use a resistor if the plan is to put it on TOW often, or get a small 48v->5v POL isolated converter for around $10 to power the led:

https://www.mouser.com/ProductDetail...fj%2Fmwg%3D%3D

Yes - you're right - more complexity than I'd like.

Maybe I shouldn't use the switch for anything other than Run / Tow, and power the LED with the factory wiring in the dash (that used to go to the stock SOC meter) that is pack voltage, unless in Tow, in which case there is no voltage, so light would go out.

This way, I would just have to reduce the pack voltage to something that wouldn't kill the LED. I'm going to 72v if the pack ever gets here from China (as much as 87.6v if the charger is on) and some of the cheap, small capacity 72v>5v or 72>12v converters I've seen on Amazon apparently don't like over voltage at all, and 72v actual is pretty much all they'll take it seems.

Is the POL device in the link you sent suitable for this?

Or what about using a resistor? I hate to "waste" power but it would be quite small I'd think. The LED in the switch draws 1.3ma at 5v. I didn't test at 12v. What would the value need to be at my current 52v nominal? Or at the ~75v the other pack will be?

Thanks!

[Sergio]

No that reducer will not work with 72v Lithium, things get expensive at those voltage levels.

Are you sure about the 1.3mA current usage by the led?

If so just do the math and use a resistor to limit the current, I think around 45kΩ x 1 watt would work at both the upper and lower range of the voltage.

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Originally Posted by Sergio

No that reducer will not work with 72v Lithium, things get expensive at those voltage levels.

Are you sure about the 1.3mA current usage by the led?

If so just do the math and use a resistor to limit the current, I think around 45kΩ x 1 watt would work at both the upper and lower range of the voltage.

Thank you!

I will check the current draw again, but I'm 90% on it. Pretty low.

I've discovered an issue with those little batteries (I have 3 or 4 different ones I've accumulated over the last few years). They power down after a period of time with "no" load, which is what the battery sees with the really low load of that one LED. One goes 3 hours, the others vary. Also, only one will charge and supply 5v at the output simultaneously. All adding complexity to that scenario...

I have to pop the back off the controller compartment (from underneath the cart) to check the run / tow connections - am I right in assuming that if there is continuity the controller sees "run" and if no continuity it sees "tow"?

Thanks for taking the time to help.

[Sergio]

On club cars the tow/run switch is just a power on/off switch, it is not a signal to the controller.

Power OFF = Tow.

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Originally Posted by Sergio

On club cars the tow/run switch is just a power on/off switch, it is not a signal to the controller.

Power OFF = Tow.

Thanks - I was unaware since I hadn't torn into it yet - thought it was just a make / break signal for the controller.

Just as a precaution, I emailed Navitas, and they echoed exactly what you said of course, but also noted (like you also just did) that the switch needs to be able to handle pack voltage.

The switch I had in mind is rated for 5A/250v AC, but has only a 5A/30v DC spec. now that I look at it. I assumed there wasn't much going through it.

I wonder if the OEM Club Car switch is even good for ~88v? Undoubtedly there are people using it at higher voltages, but it may not be rated for it.

Judging by the wire size going into / out of the switch, there can't be much current involved I wouldn't think. There is a fuse holder inside the battery compartment (split loomed so can't easily see wire colors) - is that fuse on the Run / Tow wire I wonder?

Thanks again for your insight.

[Sergio]

The tow/run powers the 15 amp fuse for all the cart electronics and also powers the "roll away" brake on Curtis OEM controller.

I am not sure how the Navitas AC uses the tow/run power but you should plan on 12ga if you are running the power to the front of the dash and back.

Aside from galvanic isolation, which is to prevent the voltage from arcing across the open switch contacts (mostly medical equipment applications), you need to worry about exceeding the switch thermal capacity.

One way to ball-park the switch power rating at different voltages is to convert the rated voltage@amps to a wattage.

So your 5A@30vdc = 150watts switch would handle about 1.75amps @ 86v.