# M3 Home Charging rate reduced



## GaryR (Mar 20, 2017)

When charging at home the rate drops from 27miles to 15 miles. Usually in hot weather. Circuit is 240V @ 30A.


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## garsh (Apr 4, 2016)

pics please


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## Ed Woodrick (May 26, 2018)

If the charging drops, that's probably because the circuit got hot. If it varies between seasons, then it sounds marginal.
Sounds like the circuit is marginal. It shouldn't be doing it.
Also may be an home AC kicking in and dropping the voltage, which then suggest it may be your feed that is marginal.


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## GaryR (Mar 20, 2017)

Thanks Ed. I believe you have hit the nail on the head. It has been over 100 during the past two days and is expected to be in the mid to upper 90’s for a week to come. I am trying to use my solar during the day but will most likely need to use the grid for a while by charging at night.


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## GaryR (Mar 20, 2017)

garsh said:


> pics please


Thanks Gar


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## GaryR (Mar 20, 2017)

Thanks Garth. See Ed’s post. Gary


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## JasonF (Oct 26, 2018)

There are usually two reasons (not related to mobile connector or on-board charger failure) that charging speed would be reduced: Either too much heat is being generated at the outlet, or the mobile connector is detecting a voltage drop characteristic of an overloaded circuit.


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## GaryR (Mar 20, 2017)

JasonF said:


> There are usually two reasons (not related to mobile connector or on-board charger failure) that charging speed would be reduced: Either too much heat is being generated at the outlet, or the mobile connector is detecting a voltage drop characteristic of an overloaded circuit.


Thanks Jason. You are spot on.


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## zosoisnotaword (Aug 28, 2017)

I had a 50A circuit installed for charging. The only availability was from the main breaker panel, which is mounted outside. They had to run the conduit through the attic to get it to the garage, so yeah, my onboard charger routinely cuts power in half due to the circuit overheating.


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## iChris93 (Feb 3, 2017)

zosoisnotaword said:


> I had a 50A circuit installed for charging. The only availability was from the main breaker panel, which is mounted outside. They had to run the conduit through the attic to get it to the garage, so yeah, my onboard charger routinely cuts power in half due to the circuit overheating.


Not sure how any of that explains why your onboard charger routinely cuts power in half due to the circuit overheating.


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## garsh (Apr 4, 2016)

iChris93 said:


> Not sure how any of that explains why your onboard charger routinely cuts power in half due to the circuit overheating.


A very long circuit run will cause a large voltage drop. It's probably limiting charging based on the voltage drop rather than overheating.


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## iChris93 (Feb 3, 2017)

garsh said:


> A very long circuit run will cause a large voltage drop. It's probably limiting charging based on the voltage drop rather than overheating.


Yup, the voltage drop could be excessive if the wire gauge was not picked correctly for the run.


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## zosoisnotaword (Aug 28, 2017)

iChris93 said:


> Not sure how any of that explains why your onboard charger routinely cuts power in half due to the circuit overheating.


I live in Alabama, and my attic stays around 435F for 10 months of the year. 95% of the cable run is in the attic, so it's nearly at the temperature limit before it's even carrying load. Haven't had any voltage drop issues.


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## iChris93 (Feb 3, 2017)

zosoisnotaword said:


> I live in Alabama, and my attic stays around 435F for 10 months of the year. 95% of the cable run is in the attic, so it's nearly at the temperature limit before it's even carrying load. Haven't had any voltage drop issues.


That doesn't make sense though because there is no way for the car to sense the temperature of the cable in the attic.


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## zosoisnotaword (Aug 28, 2017)

iChris93 said:


> That doesn't make sense though because there is no way for the car to sense the temperature of the cable in the attic.


The heat radiates to the mobile connector cable. I'll get the full 8kW for 30-60 minutes, then it will drop to 4kW for a while until it cools off.


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## iChris93 (Feb 3, 2017)

zosoisnotaword said:


> The heat radiates to the mobile connector cable. I'll get the full 8kW for 30-60 minutes, then it will drop to 4kW for a while until it cools off.


I'm still skeptical. I don't think the heat could conduct from the attic to the connector through the cable unless the connector is in your ceiling.


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## garsh (Apr 4, 2016)

zosoisnotaword said:


> The heat radiates to the mobile connector cable. I'll get the full 8kW for 30-60 minutes, then it will drop to 4kW for a while until it cools off.


Interesting. Copper is a good conductor of heat, but I would expect the effect to occur immediately if this was due to the heat radiating down from the attic through the copper wire.

I'm more inclined to suspect a poor connection somewhere causing the heating. Either at the connection to the outlet, or in the mobile connector itself, or possibly at the car-end of the connection.
Do you have access to a thermal imaging camera? It would help locate the problem.

https://www.amazon.com/Thermal-Imagers/b/ref=dp_bc_aui_C_4?ie=UTF8&node=9931455011


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## zosoisnotaword (Aug 28, 2017)

iChris93 said:


> I'm still skeptical. I don't think the heat could conduct from the attic to the connector through the cable unless the connector is in your ceiling.


Consider the thickness, conductivity, and insulation of a cable rated for 12kW. The heat from the attic portion will still spread through the ~6 ft vertical drop in the garage and anything connected to it.


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## zosoisnotaword (Aug 28, 2017)

garsh said:


> Interesting. Copper is a good conductor of heat, but I would expect the effect to occur immediately if this was due to the heat radiating down from the attic through the copper wire.
> 
> I'm more inclined to suspect a poor connection somewhere causing the heating. Either at the connection to the outlet, or in the mobile connector itself, or possibly at the car-end of the connection.
> Do you have access to a thermal imaging camera? It would help locate the problem.
> ...


I have access to a FLIR T1020, but it doesn't happen in cooler months and I rarely have to charge at home during the day, so it's not a big concern. It typically charges at 238V, so if there is a less than ideal connection, it's not bad enough to cause a noticeable voltage drop.


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## JasonF (Oct 26, 2018)

zosoisnotaword said:


> The heat radiates to the mobile connector cable. I'll get the full 8kW for 30-60 minutes, then it will drop to 4kW for a while until it cools off.


Remove the plug head from the Mobile Connector and then put it back, making sure it's completely seated flush, so there's no exposed ridge at the top of the Mobile Connector. If you can't make it seat that far, it might have been damaged by heat. A slightly loose plug head on the mobile connector causes the vast majority of overheating and current limiting.

If that doesn't fix anything, shut off the circuit breaker to the outlet, and remove the outlet from the wall. Look for melting damage, and if there is any, replace the outlet. Once you're sure it looks okay, get a powered screwdriver or drill and drive the terminal screws in until they can't possibly turn anymore. Give the wires a good solid pull to make sure they're well locked in. Then put the outlet back if all is well.

Finally, if none of that works, check the wire in the attic during an overheat condition. If it's hot to the touch (warm is ok, very hot is not) the wire guage is too small, or the wire is too low quality.

And if you're nervous about doing any of that, call an electrician. A circuit with 32 amps on it isn't a good place to guess or be close enough.


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## iChris93 (Feb 3, 2017)

zosoisnotaword said:


> It typically charges at 238V, so if there is a less than ideal connection, it's not bad enough to cause a noticeable voltage drop.


A voltage drop of just 2.5 V at 40 A is enough for 100 W of heat.


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## zosoisnotaword (Aug 28, 2017)

JasonF said:


> Remove the plug head from the Mobile Connector and then put it back, making sure it's completely seated flush, so there's no exposed ridge at the top of the Mobile Connector. If you can't make it seat that far, it might have been damaged by heat. A slightly loose plug head on the mobile connector causes the vast majority of overheating and current limiting.
> 
> If that doesn't fix anything, shut off the circuit breaker to the outlet, and remove the outlet from the wall. Look for melting damage, and if there is any, replace the outlet. Once you're sure it looks okay, get a powered screwdriver or drill and drive the terminal screws in until they can't possibly turn anymore. Give the wires a good solid pull to make sure they're well locked in. Then put the outlet back if all is well.
> 
> ...


Thanks for the advice. I've done all of that several times except for rechecking the wiring connection on the 14-50 terminals. The cable gets pretty warm, but not really hot, and there are no signs of heat damage. It won't hurt to take a look behind the outlet. Before anyone says anything, I'll be sure to open the breaker and perform a live dead live.


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## JasonF (Oct 26, 2018)

zosoisnotaword said:


> Thanks for the advice. I've done all of that several times except for rechecking the wiring connection on the 14-50 terminals. The cable gets pretty warm, but not really hot, and there are no signs of heat damage. It won't hurt to take a look behind the outlet. Before anyone says anything, I'll be sure to open the breaker and perform a live dead live.


Also possible is the outlet itself could be very low quality, so if all else fails, spending $8 on a Leviton one is worth it.

https://www.homedepot.com/p/Leviton...00689809;204377481;314101122;-_-300324414-_-N


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## Ed Woodrick (May 26, 2018)

zosoisnotaword said:


> I had a 50A circuit installed for charging. The only availability was from the main breaker panel, which is mounted outside. They had to run the conduit through the attic to get it to the garage, so yeah, my onboard charger routinely cuts power in half due to the circuit overheating.


If the circuit and the wiring is architected correctly, this should not happen. Sounds like too small of wire may have been used,


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## Ed Woodrick (May 26, 2018)

iChris93 said:


> That doesn't make sense though because there is no way for the car to sense the temperature of the cable in the attic.


It doesn't have to detect the heat, only the cause of the heat. The heat is generated by IR (current times resistance) drops along the cable, resulting in a voltage drop. The car sees the voltage decreasing, not the heat. Another way to say it if the voltage decreases, then you know that there is heat being generated somewhere.


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## gary in NY (Dec 2, 2018)

JasonF said:


> Remove the plug head from the Mobile Connector and then put it back, making sure it's completely seated flush, so there's no exposed ridge at the top of the Mobile Connector. If you can't make it seat that far, it might have been damaged by heat. A slightly loose plug head on the mobile connector causes the vast majority of overheating and current limiting.
> 
> If that doesn't fix anything, shut off the circuit breaker to the outlet, and remove the outlet from the wall. Look for melting damage, and if there is any, replace the outlet. Once you're sure it looks okay, get a powered screwdriver or drill and drive the terminal screws in until they can't possibly turn anymore. Give the wires a good solid pull to make sure they're well locked in. Then put the outlet back if all is well.
> 
> ...


A few charges back I got the notice that charging speed had been reduced due to high temperatures. Actually, the message repeated about 20 times during the charging session. Well, I've never had any trouble with my NEMA 6-50 outlet or the Mobile Connector before, so I went looking for a reason and found this thread. None of the other explanations fit my circumstances, but this post seemed worth a try. I unplugged everything; the plug from the wall, the 6-50 adaptor from the MC, and everything seemed ok. But when plugging everything back in, it seemed that the adaptor plug seated a little deeper into the MC. Next charging session: no notices. It seems that the adaptor can maybe work itself loose just hanging there, or maybe I had had not fully seated it after the last road trip back in June (I have to switch adaptors to charge at my sister's). It turned out to be a cheap fix - the best kind.


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## JasonF (Oct 26, 2018)

I got one of these a while ago to keep the weight of the Mobile Connector from pulling the plug head out:


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