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Tozz

Active Member
Jan 10, 2018
2,504
1,748
Tynaarlo
Wait, so off topic, but I keep getting errors when trying to charge at 40 amps with my UMC. First 18 months, no problem. Next six, it kept dropping to 35 amps, now I’m down to 30 amps. If I bump it up, the next morning I have charging errors and it charged at 30 Amps. All upstream is solid.

Of course, Tesla says it’s OK.
So I’ve worn out the UMC?

People often see the UMC as a charger, but it isn't. It's an EVSE (Electric Vehicle Supply Equipment). An EVSE is in reality just a fancy relay. Not much different then a wallswitch. Only here it is the car that asks the EVSE to flip the switch. Also, an EVSE can tell the car what the max. charge rate is (the max. amps drawn). But in the end, the EVSE just supplies power. It's not a charger, the charger is in the car.

Usually when UMC throw errors its because it sees things it shouldn't see. This can be overheating but more likely it are power fluctuations. When you draw more power then the outlet can supply you will see the voltage drop. For this reason the UMC throws an error and asks the car to stop charging because voltage drops are signs of issues with the power supply.

So chances you 'worn out' the umc are very small since the UMC only does measurements and switch the switch to supply power to the car. I would put my money on grid issues. Either your grid cannot supply the amount of power you draw or it is an issue with the circuit your UMC is connected to. could be a bad connection somewhere, bad plug if the UMC doesn't have a fixed connection, etc, etc.

You should be able to read from the UMC what the error is. Different errors throw different LED warning lights. Manual shows what is what
 
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Reactions: FlyinLow

Camera-Cruiser

Fully Charged
Dec 4, 2015
773
795
Fullerton, CA
People often see the UMC as a charger, but it isn't. It's an EVSE (Electric Vehicle Supply Equipment). An EVSE is in reality just a fancy relay. Not much different then a wallswitch. Only here it is the car that asks the EVSE to flip the switch. Also, an EVSE can tell the car what the max. charge rate is (the max. amps drawn). But in the end, the EVSE just supplies power. It's not a charger, the charger is in the car.

Usually when UMC throw errors its because it sees things it shouldn't see. This can be overheating but more likely it are power fluctuations. When you draw more power then the outlet can supply you will see the voltage drop. For this reason the UMC throws an error and asks the car to stop charging because voltage drops are signs of issues with the power supply.

So chances you 'worn out' the umc are very small since the UMC only does measurements and switch the switch to supply power to the car. I would put my money on grid issues. Either your grid cannot supply the amount of power you draw or it is an issue with the circuit your UMC is connected to. could be a bad connection somewhere, bad plug if the UMC doesn't have a fixed connection, etc, etc.

You should be able to read from the UMC what the error is. Different errors throw different LED warning lights. Manual shows what is what

Thank you.

The UMC always shows green LEDs. So same UMC, but three years ago charging at 40AMPS no problem. Then, the car started dropping to 35AMPS, and now it drops to 30AMPs regardless if I start at 40 or 35.

I replaced the wall socket I plug into and verified all wires are good.

It will be interesting to see what my future model 3 reports when using the same circuit.
 

Richt

Just traveling down the road...
Dec 20, 2017
122
52
Seattle
Ok one thing analyses like these don’t cover is how base loads work. I had the (good) fortune to be part of an energy trading company and the first thing you learn is that in many regions the “base” load is powered by coal plants or diesel plants that literally can’t shut off. So the price can be literally negative. That is the utilities do have to have some sort of average but the actual marginal cost at night is negative because you can’t store electricity so it has to go into heat or somewhere.

So when you charge your EV at night in many regions even with brown coal, you are by adding to the carbon footprint. Those plants have to run anyway. You might still want to install solar because economically it meaningful but if you care about green house gases (that might fit in somewhere for some of us) EVs are really a big win.

The second thing I didn’t see covered is the maintenance cost of EVs and their longevity vs ICE. You covered the first 10K but over 100K miles it’s quite different. I can dig it up but for most folks, maintenance costs are ¼ less. Finally no one knows the ultimate lifespan of EVs yet but looks like preliminary data is the motors are good for 500K-1M miles. And the batteries 300K at least. So the total cost of ownership Is much lower. You might not own a car to 1M miles of course but it goes into the “fleet” so someone else will use it.
 

Richt

Just traveling down the road...
Dec 20, 2017
122
52
Seattle
Oops that should say NOT adding to the carbon footprint. Sorry editing with this forum on an iPhone is pretty broken.
 

brkaus

Well-Known Member
Jul 8, 2014
7,720
6,251
Austin, TX
Thank you.

The UMC always shows green LEDs. So same UMC, but three years ago charging at 40AMPS no problem. Then, the car started dropping to 35AMPS, and now it drops to 30AMPs regardless if I start at 40 or 35.

I replaced the wall socket I plug into and verified all wires are good.

It will be interesting to see what my future model 3 reports when using the same circuit.

There have been reports of UMC going bad. Usually the GFCI circuit and it simply stops working and shows an error. It’s also possible it’s sonething on the utility side.

Do you see voltage change as the current draw ramps up? (Looking at the center screen).

What does the voltage do over time? (Center screen)

Suggest checking the circuit breaker for heat too.

If you have a volt meter, you can check the voltage elsewhere in the house and see if that changes? Some UPS gave voltage display too.

You could borrow a UMC and see if it dies the same? Or try your UMC elsewhere?

The model 3 has a 32a max umc. So that may mask the problem.


Btw - off topic for this thread.
 
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FlyinLow

Enjoy the journey
Feb 5, 2018
335
328
29036
To get back on topic...

Brando re-posted an interesting video in another thread. After 41 minutes a great total cost of ownership comparison is made between the Toyota Carolla, BMW 328i and Tesla Model 3.


Highlights:
The only option to protect ICE vehicles is to prevent the sale of BEVs. This is happening in a large number of U.S. states who don’t allow the sale of Tesla.

When people have a choice they will vote with their dollar.

When the used Tesla Model 3 market explodes after the Model Y production ramp I predict we will have our mass market EV adoption. That will happen about the same time as the Niro, Ioniq, etc become mainstream BEVs.
 

FlyinLow

Enjoy the journey
Feb 5, 2018
335
328
29036
The classic question answered...

“Aren’t EVs so bad for the environment to build that they will never be cleaner than internal combustion cars?”

A video answer with pictures...

 

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