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Home charging fluctuates from 8 kw to 4 kw

Bodyhauler

Member
Jun 20, 2019
143
254
Cedar Park, Tx
I have a Nema 14-50 outlet in my garage and have my Mobile Charging Unit plugged in for charging. Recently I've noticed my charging fluctuates from the max of 8 kw to 4 kw. It switches back and forth while charging. I haven't noticed this before and wondered if it is just with warmer temps (Upper 80's - 90's in garage) or is my Mobile Charger becoming faulty.
 

mongo

Well-Known Member
May 3, 2017
12,904
38,113
Michigan
I have a Nema 14-50 outlet in my garage and have my Mobile Charging Unit plugged in for charging. Recently I've noticed my charging fluctuates from the max of 8 kw to 4 kw. It switches back and forth while charging. I haven't noticed this before and wondered if it is just with warmer temps (Upper 80's - 90's in garage) or is my Mobile Charger becoming faulty.

I think your S has dual chargers, one may be going bad/ overheating.
 
Apr 7, 2020
54
40
Houston
Either the above or the wiring in your home is heating up. To test this theory set you charging limit to something in between 4 and 8kw, like 5. If the lower limit solves the problem then its likely wiring in the house problems. If it still goes down to 4kw and back to 8 then the onboard charger is likely the problem.
 
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Reactions: croman

mongo

Well-Known Member
May 3, 2017
12,904
38,113
Michigan
I believe even a single charge has two units inside.

Probably. The dual charger was 80 Amp anyway, not 40A so I was off on that.

Either the above or the wiring in your home is heating up. To test this theory set you charging limit to something in between 4 and 8kw, like 5. If the lower limit solves the problem then its likely wiring in the house problems. If it still goes down to 4kw and back to 8 then the onboard charger is likely the problem.

Yeah, UMC will throttle based on temperature.

The vehicle will reduce charge current by 25% current on excessive voltage drop. So it doesn't seem to fit the 4kW/8kW symptom.
 

r1200gs4ok

Active Member
Jul 17, 2019
1,340
450
Irvine
Maybe, you can also double check that the plug adapter is fully seated (UMC to 14-50 or whatever you are using).
and all wires are securely screwed down.....if the plug is warm or hot you got wiring issues....my Tesla Nema 14-50 was fluctuating between 40kW and 30 kW.....everything was ok ....turned out to be the Tesla charger....it was replaced with a hard wired unit
 

Bodyhauler

Member
Jun 20, 2019
143
254
Cedar Park, Tx
I had the mobile repair guy at the house today for a handle repair and asked him about the charging unit fluctuating and he told me to make a new repair order and Tesla will bring me out a new UMC replacement free.
 

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