Question Charge rate reduction experience?

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Jim H

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#1
Has anyone notice a reduction in charging rate with home charging?
I have a 30amp NEMA 14/50 plug that I charge at 24amps. Lately during charging, the rate is reduced to 14amps. I can manually raise the rate back up to 24amp, but will reduce back down to 14amp again.
Just started doing this recently, maybe after an update, but unsure when this actually started.
I've used the same setup from day 1 with the car, so nothing was changed with my charging.
 

garsh

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#2
If the car senses a voltage drop, it'll reduce the charging rate. So you might be having issues with your electrical service.

Otherwise, make sure the Mobile Connector is seated fully into both the wall outlet and the car. If you have a thermal imager or other type of thermometer, you can check the temperature at the car charging port, the outlet, and the breaker within your electric service panel to make sure you don't have a bad connection somewhere that's getting too hot. That would also be sensed by the car as a voltage drop.
 

JasonF

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#3
Most of the time, this is caused by the plug head pulling out of the Mobile Connector, causing enough resistance to force the charging to slow down. Pull the plug head off completely, and reinsert it, making sure it's seated fully.

If that fails:

If you don't have an infrared thermometer as noted above, wait until the car is charging for a while, and then stop charging and unplug the 14-50. Feel around the edges of the plug and see if it feels hot. Not just warm, but alarmingly hot. If that is the case, you might have had a cable inside the outlet loosen in its retaining screw. This can happen from plugging/unplugging the Mobile Connector a lot, so you might want to consider either getting a second Mobile Connector to keep plugged in permanently at home (which is what I did) or get a Wall Connector (or some other installed charger).

Finally, if all of that passes, check the temperature of the circuit breaker. If it's hot, it could be loose and not snapped all the way down into the bus bar. You could also check the temperature of the main breaker too. If that or the incoming wires are very hot, there could be a malfunction with the breaker box, or you could be using more amps than your service is rated for.

And if everything seems nice and cool and perfectly fine, except for the charging amps drop, check the voltage at the outlet. If it's too low, you could have an issue with the service to your house. But if that's fine too, you've zeroed in on a bad Mobile Adapter and would have to contact service.
 

JasonF

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#5
It'll still be warm due to normal use, just not burning-your-hand hot, right?
Yes, I'm only talking about frighteningly hot. Human hands are very good at detecting that right away, even if they're not being burned. If you've ever touched a cord or outlet that's being overloaded, it doesn't look like much to the eye, but your hand can definitely tell.
 
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#6
Thanks for the suggestions. Turned power off to the 14/50 and retighten all the wire connections, which were tight. Looked for any signs of excessive heat issues, saw a little but nothing bad. Does get hot over the summer when garage is 80's, not so much this time of year. Stuck receptacle back in to box in wall, left face plate off to keep an eye on it, and it's back to 24amp for a good 4hr charge with no problems.
I still think I'm going to a 50amp breaker and another 14/50 outlet with correct wire for a second choice. These days having a second 14/50 outlet in the garage is probably not a bad ideal.
 

garsh

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#7
Thanks for the suggestions. Turned power off to the 14/50 and retighten all the wire connections, which were tight. Looked for any signs of excessive heat issues, saw a little but nothing bad.
Did you also remove and re-seat the NEMA 14-50 adapter to the Mobile Connector, as @JasonF suggested?
 

NR4P

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#8
Car and Tesla App should show voltage and Amps. Home nominal voltage for a 240 line is 238-245V .
Business is 208V.

When it drops to 14Amps, what does car show on the screen for voltage?

For reference, when I charge at work with Nema 14-50, line is about 196-201V, 30A, 6KW.