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cost/ benefit of installing a nema plug vs tesla wall connector

Rocky_H

Well-Known Member
Feb 19, 2015
6,660
7,953
Boise, ID
I used to only use the mobile connector in my garage until recently. I was talking to a Tesla Service tech and we started talking chargers. In his experience constant use of the mobile leads to a lifespan of about 2 years. The Wall Connector is more robust and designed for long term. This past weekend I wired in a wall connector to a 50A circuit and it’s been great. Now I just take the mobile on road trips.
I think that's a thing where there is a grain of truth but needs more explanation. It's not just that they die quickly if used daily. Tesla seems to design their charging products for "just barely" at their maximum rated amps. All of their charging equipment had some pretty bad failure rates when run at maximum amps daily. 1st gen UMC at 40A, the 1st and 2nd gen wall connectors running at 80A, and apparently the 2nd gen UMC running at 32A all get pretty hot and had some noticeable number of early life failures when run at max amps daily. And when done every single day that way, you get pretty significant swings of heat cycle of hot/cold/hot/cold, which is some materials stress on solder joints and electronics, etc.

So when people ask about, "Should I turn down my charging amps to protect the battery?" The answer is yes/no. The battery absolutely doesn't care, because the charging rate on home circuits is so low. But to maybe preserve the life of your charging equipment to make it last longer? Yeah, that probably isn't a bad idea. Turning it down just a bit from its maximum level makes it run cooler and usually adds significant time to its functional life. I have been running my old 1st generation UMC at about 31A instead of 40A to keep it cooler, and it's still going for over 7 years.
 
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TSLY

Member
Jul 28, 2021
64
19
Los Angleles
Live in SoCal, preparing for MYLD delivery. Intended to install NEMA but electrician suggested Wall Connector better option because I'd want to have the mobile connector with me on road trips, and in general, which requires lots of unplugging/replugging. Just purchased Wall Connector with 30% rebate.
 

TomServo

Active Member
Apr 10, 2014
1,542
993
Belleville IL
I think that's a thing where there is a grain of truth but needs more explanation. It's not just that they die quickly if used daily. Tesla seems to design their charging products for "just barely" at their maximum rated amps. All of their charging equipment had some pretty bad failure rates when run at maximum amps daily. 1st gen UMC at 40A, the 1st and 2nd gen wall connectors running at 80A, and apparently the 2nd gen UMC running at 32A all get pretty hot and had some noticeable number of early life failures when run at max amps daily. And when done every single day that way, you get pretty significant swings of heat cycle of hot/cold/hot/cold, which is some materials stress on solder joints and electronics, etc.

So when people ask about, "Should I turn down my charging amps to protect the battery?" The answer is yes/no. The battery absolutely doesn't care, because the charging rate on home circuits is so low. But to maybe preserve the life of your charging equipment to make it last longer? Yeah, that probably isn't a bad idea. Turning it down just a bit from its maximum level makes it run cooler and usually adds significant time to its functional life. I have been running my old 1st generation UMC at about 31A instead of 40A to keep it cooler, and it's still going for over 7 years.

So running a WC at 40 amps is the best way to avoid ANY issues?
 

Rocky_H

Well-Known Member
Feb 19, 2015
6,660
7,953
Boise, ID
So running a WC at 40 amps is the best way to avoid ANY issues?
I wouldn't say a fixed number, but something like that. It seems like a pretty significant reduction in the heat level just turning things down from the highest maximum level it is made to do.

And to address people who may criticize this, I am not saying that running this at maximum level any particular time, or once a month or something, is going to instantly cause a problem. I view this more in the long term wearing things out issue. How many degrees difference do you have between the warm condition when it's running, and the totally cooled off temperature when it sits for the next 15-20 hours unused? When you are doing that 300+ days a year, the larger that temperature swing is, just makes for a bit more stress on the materials over time. And if the car takes 5 hours instead of 4 hours to finish charging while you are asleep, that doesn't make any difference in your use of it, so why not be a bit easier on the equipment?
 

Silicon Desert

Active Member
Oct 1, 2018
3,598
3,493
Sparks NV / GF 1
I went with the receptacle and a mobile connector. That way, if the connector fails/gets damaged, or we get a second EV and want a dual EVSE, or we go somewhere that we’d want the slightly faster 40-amp charging, we can disconnect and make the change much more easily (and without an electrician).

I actually just mounted the connector today, in fact.
yup, I did the same. Since we may get another brand EV in the future.
 
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rjpjnk

Member
Mar 12, 2021
663
343
NJ
I wouldn't say a fixed number, but something like that. It seems like a pretty significant reduction in the heat level just turning things down from the highest maximum level it is made to do.

And to address people who may criticize this, I am not saying that running this at maximum level any particular time, or once a month or something, is going to instantly cause a problem. I view this more in the long term wearing things out issue. How many degrees difference do you have between the warm condition when it's running, and the totally cooled off temperature when it sits for the next 15-20 hours unused? When you are doing that 300+ days a year, the larger that temperature swing is, just makes for a bit more stress on the materials over time. And if the car takes 5 hours instead of 4 hours to finish charging while you are asleep, that doesn't make any difference in your use of it, so why not be a bit easier on the equipment?
I don't think we have any hard data on the life expectancy of the chargers as a function of operating current, but I do agree that in general lower is better. If there is no hurry to charge the car then it makes sense not to rush things. In fact, I would say that the lowest current you can operate at that still allows the car to be fully charged by morning is the best choice. Whether it's enough better to make a difference, I have no idea.

I currently charge at 40 Amps
 

jcanoe

Active Member
Oct 2, 2020
3,256
3,237
Maryland
By lowering the charging amperage you might extend the life of the equipment but by how much is unclear. There is a certain amount of fixed overhead while charging; heat losses in wiring and on-board charger voltage conversion heat losses. Other overhead would include coolant circulating pumps to maintain the battery temperature. Reducing the time to complete the charging cycle minimizes the total overhead. This is a major component of the reason that charging at 240V is more efficient than charging at 120V, with 240V charging being up to 10% more efficient. When you lower the amperage, i.e. the power level you are necessarily extending the time needed to charge. You won't benefit as much from the charging efficiencies of 240V charging at the reduced level.

Vehicle charging equipment wears out from physical use as well as age. Every time you move the charging cable around your vehicle you are adding wear to this cable. Every time you plug in the charging connector this is adding wear to the charging connector and the charging port. Eventually this equipment will wear out. Electric vehicle service/supply equipment manufacturers will generally only provide a warranty for 3 years.

Another consideration, not generally discussed, is that by international treaty agreement most modern electronic equipment is assembled using lead-free solder. This type of solder is known to break down, causing faulty connections after ~10 years.
 
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Rocky_H

Well-Known Member
Feb 19, 2015
6,660
7,953
Boise, ID
I don't think we have any hard data on the life expectancy of the chargers as a function of operating current, but I do agree that in general lower is better.
I would not agree with leaving it that open ended. It's not a continual benefit to keep going down to 20 or 15 or 5 amps. That's not impacting this heat cycling issue I'm talking about, and has the other negatives that @jcanoe is talking about by running charging for an excessively long time. My point is more about just turning it down by maybe 5-10 amps down from the top end maximum level. That first little bit does a lot for reducing the heat to where it's just barely getting warmer than room temperature, and you've got most of the benefit there already without lowering the amps down a lot more.
 

Nrvna76

MYLR7 Blue/White with Tow. EDD January.
Aug 20, 2021
55
126
Albany NY
Really thankful there’s so much great info on this site including chargers. I’m pretty sure I’m going with the wall connector once they are back in stock. I will have to pull out an old 30 amp dryer breaker and install a 60amp, but the connector will be right next to the panel in my garage so it seems pretty easy and lots of videos available.
 

rjpjnk

Member
Mar 12, 2021
663
343
NJ
Just be sure the wire on that old 30 amp circuit can handle the 60 amp breaker and wall connector. According to the electricians on here that means 6 gauge THHN (loose wire) in conduit or 4 gauge romex.
 

Nrvna76

MYLR7 Blue/White with Tow. EDD January.
Aug 20, 2021
55
126
Albany NY
Just be sure the wire on that old 30 amp circuit can handle the 60 amp breaker and wall connector. According to the electricians on here that means 6 gauge THHN (loose wire) in conduit or 4 gauge romex.
Not planning to reuse the wires. I’ll pull them and cap them or something and add new wire to the wall connector.
 
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Sacramento

2021 Tesla Model Y LR AWD
Mar 13, 2021
50
73
Sacramento, CA
Tesla Tax
Tesla tax! I wanted to change out an old Zinsco panel when I added a HPWC that I bought directly from Tesla and got a quote from a "Tesla recommended" electrician– $4,500. I told him I was installing the charger myself and just needed him to make the connections at the new panel. Still $4,500 because he had to "set up" the charger. So I bought a Square D Homeline 200 amp panel and all the breakers at Home Depot for under $1,000 and found an electrician who installed the new panel for $1,200. I "set up" the charger myself in about five minutes.
 

Teslitored

Member
Jul 9, 2021
82
21
USA
I was planning to install a 240 v outlet in my garage in case we get a non-Tesla EV in the future. But, I found out that my city is offering up to $500 rebate for a wall charger and up to $500 for an electrician.....
 

rjpjnk

Member
Mar 12, 2021
663
343
NJ
I was planning to install a 240 v outlet in my garage in case we get a non-Tesla EV in the future. But, I found out that my city is offering up to $500 rebate for a wall charger and up to $500 for an electrician.....
No brain required on this one! 👍
 

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