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72A Home Charging - Super Hot Cable

Aggmeister2010

Active Member
Dec 26, 2018
1,230
1,103
TX
Hey Folks,

My 2016.5 P90D has 72a charging, and I have a Gen 1 wall charger that can support it.

What I've noticed, though, is that if I charge at 72a, the fans run full tilt, the charge cable gets "hey that kinda hurts" hot, and my whole garage gets pretty warm.

If I bump it down to 50a, the car is quiet, all is well, it just takes a bit longer.

Anyone else running 72a experience quite a bit of heat? The car doesn't throw any errors, so I'm assuming this is expected and normal, but the fans running at 100% and the hot charge cable gave me pause.
 

Muzzman1

Active Member
Feb 8, 2014
1,046
1,848
Los Angeles
Yeah, same. Both of my Wall Connectors are 80A variety.
My previous dual charger MS and my Wife's 2016MX with 72A would heat up the cables to the point where I felt it was unsafe.
As a result, for the last 4-5 yrs I've been just charging at 40A each unless we are in a pinch to get a quick charge. (that has only happened a handful of times over the yrs)
 
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Reactions: Gixx1300R
Our 2015 P85D came with dual chargers and a Gen 1 High Power Wall Connector on a 100A breaker (80A max. charge rate). Charging at 80A definitely heated up the HPWC charge plug and socket VERY hot as well as the charge cable near it. Tesla Ranger replaced our HPWC charge cable and cleaned our charge port and the charge plug heat from from very HOT to warm, so I dropped the charge rate 20% from 80A to 64A and our HPWC charge plug, socket and cable were MUCH cooler. Charge time is only 20% longer which is irrelevant since I have our P85D charging scheduled to complete before 8:00 AM (when our electric rate goes up). I've occasionally charged at 80A and our HPWC plug, cable and vehicle charge port are definitely warmer... but not crazy HOT like it was with the original "defective" HPWC charge cable (attached).
 

dark cloud

Active Member
Apr 14, 2018
2,475
2,996
BC
Hey Folks,

My 2016.5 P90D has 72a charging, and I have a Gen 1 wall charger that can support it.

What I've noticed, though, is that if I charge at 72a, the fans run full tilt, the charge cable gets "hey that kinda hurts" hot, and my whole garage gets pretty warm.

If I bump it down to 50a, the car is quiet, all is well, it just takes a bit longer.

Anyone else running 72a experience quite a bit of heat? The car doesn't throw any errors, so I'm assuming this is expected and normal, but the fans running at 100% and the hot charge cable gave me pause.
Kind of reminds me of the switch from incandescent to led light bulbs, where one converts that heat energy into light output instead and saves some money on the energy bills.
 

ucmndd

Well-Known Member
Mar 10, 2016
10,190
20,020
California
It's slightly more efficient since the computer isn't running while you're not charging. It's minimal but it's a thing.
Given resistance/heat rises as the square of the current, there’s a practical limit to this. Without doing the math, I’d guess that 72/80 amp charging is actually LESS efficient than somewhere around 40 amps, all things considered.
 
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gavine

Petrol Head turned EV Enthusiast
Apr 1, 2014
2,639
2,226
Philadelphia, PA
heat is relate to the square of the amperage, so every amp greatly increases heat.

power (hence heat) is current squared * resistance.

Does time have any affect on this formula? I would think sustained charging would "heat soak" the cables as well. For instance, charging at 72A for 5 minutes would accumulate less heat in the cables than charging at 40A for 4 hours. But yes, higher amperage definitely generates more heat, more quickly.
 
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dark cloud

Active Member
Apr 14, 2018
2,475
2,996
BC
Does time have any affect on this formula? I would think sustained charging would "heat soak" the cables as well. For instance, charging at 72A for 5 minutes would accumulate less heat in the cables than charging at 40A for 4 hours. But yes, higher amperage definitely generates more heat, more quickly.
Yes, the higher the temperature the higher the resistance, at the rate of 0.39% per degree Celsius. No wonder why V3 superchargers keep cables cool via liquid cooling.

Temperature Coefficient of Copper.
 
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I work mobile power for the Space Force (yes, it's a real thing) and let me tell you, 150 continuous amps on 2/0 (even 4/0) wire gets extremely hot. 150-160F using a FLIR. Copper can handle up to 190-ish but it shouldn't get that hot. Just make sure those connections are tight!!
I also am seeing very hot cabling during charging. Present reading is 138 degrees. But based on the response above, I guess this is okay.
 
The car is running the A/C to keep the battery from overheating. That heats the garage. The hotter garage also raises the cable temperature, since the power loss in the cable causes a temperature rise starting from the ambient air temperature. Of course summer (in Texas as well) doesn't help.

Open or vent the garage to reduce the garage temperature gain. If one end of the cable is significantly hotter than the other that could indicate a lose connection to the Wall Connector or at the charge port. Your equipment is getting older and the connections might be loosening a bit. As mentioned above, reducing the amps will reduce the heating effect on both the cables and the battery.
 

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