Run/Tow switch heating up?

mattadata · 02-08-2016, 06:15 PM

I noticed the thermal labels I used on my Run/Tow switch had some 'burns'. This has me a little concerned. It doesn't take much heat to turn the labels black. The switch has never felt warm. I don't see anything that could have caused an arc.

Any ideas how the burn got there?

cgtech · 02-08-2016, 11:59 PM

Droplet of battery acid? Take a small piece of that label material and touch it to the bottom of one of your battery caps to see how the label reacts.

Volt_Ampere · 02-09-2016, 08:56 AM

That has to be an acid burn. There is no significant current through that switch so it can't get hot.

JohnnieB · 02-09-2016, 09:45 AM

It depends of what the definition of is is.

Personally, I consider all the current that powers the electronics in the XCT controller, all the current that flows through external switches connected to the controller, the ITS current and the solenoid coil current as significant, but I agree heat from the Run/Tow switch didn't make the black spot the thermal tape.

The tape is adhered to some fairly thick metal, which is very likely to be an excellent thermal conductor, so a catastrophic failure of some kind that was significant enough to get the switch hot, would blacken the thermal tape on both sides in a circular pattern radiating from the hole where the switch is physically attached to the solenoid mounting bracket.

It is most likely caused by acid, but maybe not an actual drop of electrolyte.

The air under the seat contains acidic vapors, so all that is needed is a drop of water of collect them.

Also, the typical pH of human sweat is in the 4.6 to 5.5 range, so just a drop of sweat might have caused the thermal tape to discolor over time.

mattadata · 02-09-2016, 09:50 AM

I was checking the water level in all batteries when I noticed it. A drop could have flown out when I was popping the tops off. I will try a little science experiment tonight by placing a drop of battery fluid on a different piece of thermal tape.

No other symptoms....cart runs great!

mattadata · 02-09-2016, 06:30 PM

Test results:
No discoloration from battery fluid.

cgtech · 02-10-2016, 02:45 PM

Hmmm...

mattadata · 02-11-2016, 10:09 AM

After 24 hours, it has changed colors, but still looks different than the other label. I will replace the label on the cart and see if it happens again.

02-08-2016, 06:15 PM	#1
mattadata Gone Wild Join Date: Dec 2014 Location: Dallas, TX Posts: 247	Run/Tow switch heating up? I noticed the thermal labels I used on my Run/Tow switch had some 'burns'. This has me a little concerned. It doesn't take much heat to turn the labels black. The switch has never felt warm. I don't see anything that could have caused an arc. Any ideas how the burn got there?

02-08-2016, 11:59 PM	#2
cgtech Over This Interview Is... Join Date: Jun 2012 Location: AZ Posts: 17,449	Re: Run/Tow switch heating up? Droplet of battery acid? Take a small piece of that label material and touch it to the bottom of one of your battery caps to see how the label reacts.

02-09-2016, 08:56 AM	#3
Volt_Ampere Gone Wild Join Date: May 2012 Location: Rio Verde, Az Posts: 7,173	Re: Run/Tow switch heating up? That has to be an acid burn. There is no significant current through that switch so it can't get hot.

02-09-2016, 09:45 AM	#4
JohnnieB Techno-Nerd Join Date: Jun 2011 Location: West Virginia Posts: 19,654	Re: Run/Tow switch heating up? It depends of what the definition of is is. Personally, I consider all the current that powers the electronics in the XCT controller, all the current that flows through external switches connected to the controller, the ITS current and the solenoid coil current as significant, but I agree heat from the Run/Tow switch didn't make the black spot the thermal tape. The tape is adhered to some fairly thick metal, which is very likely to be an excellent thermal conductor, so a catastrophic failure of some kind that was significant enough to get the switch hot, would blacken the thermal tape on both sides in a circular pattern radiating from the hole where the switch is physically attached to the solenoid mounting bracket. It is most likely caused by acid, but maybe not an actual drop of electrolyte. The air under the seat contains acidic vapors, so all that is needed is a drop of water of collect them. Also, the typical pH of human sweat is in the 4.6 to 5.5 range, so just a drop of sweat might have caused the thermal tape to discolor over time.

02-10-2016, 02:45 PM	#7
cgtech Over This Interview Is... Join Date: Jun 2012 Location: AZ Posts: 17,449	Re: Run/Tow switch heating up? Hmmm...

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02-09-2016, 09:50 AM	#5
mattadata Gone Wild Join Date: Dec 2014 Location: Dallas, TX Posts: 247	I was checking the water level in all batteries when I noticed it. A drop could have flown out when I was popping the tops off. I will try a little science experiment tonight by placing a drop of battery fluid on a different piece of thermal tape. No other symptoms....cart runs great!

02-09-2016, 06:30 PM	#6
mattadata Gone Wild Join Date: Dec 2014 Location: Dallas, TX Posts: 247	Test results: No discoloration from battery fluid.

02-11-2016, 10:09 AM	#8
mattadata Gone Wild Join Date: Dec 2014 Location: Dallas, TX Posts: 247	After 24 hours, it has changed colors, but still looks different than the other label. I will replace the label on the cart and see if it happens again.

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