High Power Wall Charger (HPWC) vs NEMA 14-50 Direct Plug

[Naonak]

Yes, I run mine a bit lower too. I think @Naonak 's claim about the UMC having "unstable power delivery" is baloney. I do agree it's a bit underbuilt, so I could see it having some trouble if you're trying to run it at the max 40A. But from 5 up to about 35, it's not "unstable".

So my claim is baloney, but you don't run your UMC at it's rated capacity... So which is it, is it baloney, or you run your UMC at rated capacity without issues?

The UMC has unstable power delivery at 40a. Guaranteed. A brand new one might be fine for a bit, but it will eventually have trouble delivering a consistent 40a, absolutely and without question. It will happen sooner, rather than later if you charge every day.

 

[Blup85]

Think of it this way, the HPWC is rated for 80 AMPS, the Travel charger (UMC) is rated for 40 so obviously the UMC is working a heck of a lot harder than my HPWC. I can tell because running 40 amps on my UMC gets warm, my HPWC doesn't even sweat..and heat is lost efficiency ( granted a very small amount). When I bought my first p85, the original owner only used the UMC as his charging source, it had burn marks at the 14-50/Tesla connection (still worked) and Tesla replaced it at my first service. I only use my UMC for Travel and "emergency" situations... like charging at friends houses
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[isjka]

Do it. Also, the best solution is to put a 100A sub-panel in the garage so that the second circuit is even easier to install. I planned ahead and I have a 14-50 socket for each garage space, but in retrospect I should have done a sub-panel so that I could share that 100A and charge one car faster if needed.

Thanks for all the feedback. I was quoted for the sub-panel in the garage running 125 amp, but that added an additional $825 or so to the quote. Seems a little steep especially given the fact I'm not sure if the wife in the near term will buy an electric car.

 

[miimura]

Thanks for all the feedback. I was quoted for the sub-panel in the garage running 125 amp, but that added an additional $825 or so to the quote. Seems a little steep especially given the fact I'm not sure if the wife in the near term will buy an electric car.

When I had my house built in 2011 I had no electric cars but I still put in the two 240V circuits during construction for $250 each. I had no plans to get an electric car, but I was certain that during the life of the house, they would be used.

You should consider the cost of the second one in the future after you have saved the $825 today. Now, if you think you're going to move before you need the second one, that's a different story.

 

[Rocky_H]

So my claim is baloney, but you don't run your UMC at it's rated capacity... So which is it, is it baloney, or you run your UMC at rated capacity without issues?

False dichotomy. You were saying the UMC was an unstable power delivery device, period. You did not say it was the case only at maximum level, which is more accurate. I was saying that the UMC or the wall connector can both be so running at their maximum levels.

The UMC has unstable power delivery at 40a. Guaranteed.

And so does a wall connector running at 80A--plenty of reports here of them not keeping up 80 level or handles melting, losing connection, etc. I would turn that down if I had one of those instead.

 

[Naonak]

False dichotomy. You were saying the UMC was an unstable power delivery device, period. You did not say it was the case only at maximum level, which is more accurate. I was saying that the UMC or the wall connector can both be so running at their maximum levels.


And so does a wall connector running at 80A--plenty of reports here of them not keeping up 80 level or handles melting, losing connection, etc. I would turn that down if I had one of those instead.

It's not a false dichotomy. The vast majority of people run the UMC at 40a, and each car can charge at max capacity. Unlike the HPWC, which can handle more power than most cars can accept and therefore are not run at full capacity. The default assumption is that the UMC is running @40a and I'm saying it's unstable. If you really want to be that pedantic to make yourself feel correct, then by all means, that's cool.

Regardless, however, since we are being pedantic, you claimed that the UMC is not unstable. You did not say it's not unstable at lower power levels. You made a blanket claim that my statement was dubious. You did not say it was the case at less than maximum power levels, which is more accurate.

The UMC is unstable at the normal power levels people charge at. The HPWC is not. In fact, I will go so far as to say the HPWC is not unstable even at maximum power levels, unlike the UMC.

 

[bob_p]

Most of the charging done with our S P85 since early 2013 has been on an HPWC set to 80A - and we haven't had any problems.

Since our S 100D has arrived, we moved the P85 over to a 14-50 outlet - and it's charged fine.

The only charging problems we've had have been traced back to issues with the power being supplied to the house - we've had two instances with power surges that damaged the onboard chargers in the P85. First time, the secondary 40A charger was damaged, which limited the car charging to 40A until the secondary charger was replaced. The second time was during Hurricane Harvey, when the primary charger was damaged, and required replacement. Both times, Tesla replaced the chargers under warranty.

While Tesla claims the onboard chargers have surge protection, we're considering adding a surge protector in the breaker panel used by both of our Model S cars.

 

[Brass Guy]

If the UMC fluctuates between 39 and 40 amps, I suppose you can call it "unstable." But from my perspective, if the car is charged every morning, it's stable.

 

[Naonak]

The fluctuations itself aren't a huge deal. It's the indication that something is wrong, though. That's what the problem is. If the UMC is operating that close to the edge that it's unable to deliver a constant amount of power, it means the unit is going to fail sooner rather than later.

In my case, this was brought to my attention because over time (My 2012 has 110k miles on it), the UMC became increasingly unable to deliver power in a stable fashion and eventually the car throttled down to 30a, which is a pain. After switching all my Teslas over to HPWCs, I've never had a single issue and power is very stable at a constant 40a throughout a full charge.

The UMC was replaced by Tesla, fortunately. They said it wasn't an uncommon problem with high mileage UMCs.

 

[Rocky_H]

After switching all my Teslas over to HPWCs, I've never had a single issue and power is very stable at a constant 40a throughout a full charge.

So you're running a device at half it's rating and then beaming about how much better it is than something running at maximum--brilliant.

 

[cybergates]

My house has a 200 Amp panel breaker (newer panel recently redone after solar added). Everything is gas appliances and it's So-cal (lots of A/C use in the summer). Without doing official load calculations, would u say it's a fair bet my house support 2 x 14-50? I currently use a 14-30 repurposed electric dryer circuit. I would get rid of the 14-30 and ask the electrician to run 14-50 x 2 while doing a room addition.

 

[ran349]

So my claim is baloney, but you don't run your UMC at it's rated capacity... So which is it, is it baloney, or you run your UMC at rated capacity without issues?

The UMC has unstable power delivery at 40a. Guaranteed. A brand new one might be fine for a bit, but it will eventually have trouble delivering a consistent 40a, absolutely and without question. It will happen sooner, rather than later if you charge every day.

I charge every day with my 14-50 at 40a for over 2 1/2 years, and over 45k miles on my car. It has been extremely stable the whole time, and still is now. Not to say it will never fail, but it hasn't shown any signs of it so far.

 

[davewill]

My house has a 200 Amp panel breaker (newer panel recently redone after solar added). Everything is gas appliances and it's So-cal (lots of A/C use in the summer). Without doing official load calculations, would u say it's a fair bet my house support 2 x 14-50? I currently use a 14-30 repurposed electric dryer circuit. I would get rid of the 14-30 and ask the electrician to run 14-50 x 2 while doing a room addition.

It's a fairly safe bet, but no means assured. You may find that the dryer circuit is there because of code requirements and you may not want to try to eliminate it. If you don't have an appliance plugged into it, it might not significantly change the load calculation anyway. Besides, you may get a powerwall in the future and want to capitalize on it with an electric dryer.

 

[Rocky_H]

My house has a 200 Amp panel breaker (newer panel recently redone after solar added). Everything is gas appliances and it's So-cal (lots of A/C use in the summer). Without doing official load calculations, would u say it's a fair bet my house support 2 x 14-50? I currently use a 14-30 repurposed electric dryer circuit. I would get rid of the 14-30 and ask the electrician to run 14-50 x 2 while doing a room addition.

Since you are wanting to put in two charging places but a little concerned about capacity, I think this would be a good setup for two wall connectors sharing a circuit. Then you can put both on a 60 or 80 amp circuit instead of having to have room for 100 because of the 50 times two.

 

[Naonak]

I charge every day with my 14-50 at 40a for over 2 1/2 years, and over 45k miles on my car. It has been extremely stable the whole time, and still is now. Not to say it will never fail, but it hasn't shown any signs of it so far.

Can I ask what does the button on your UMC handle look like? Is it a solid piece of plastic with a little target dot in the middle, or is it a cutout tab button?

I have a suspicion that the target dot style is more prone to failure than the tabbed style.

 

[ran349]

Can I ask what does the button on your UMC handle look like? Is it a solid piece of plastic with a little target dot in the middle, or is it a cutout tab button?

I have a suspicion that the target dot style is more prone to failure than the tabbed style.

I have the cutout tab button.

 

[brkaus]

@Naonak I've noticed some fluctuations on an HPWC at 48a. I believe the cause is the charger in the car is actually limited by power and not current. The voltage at my main meter runs 244-248 volt range. When the voltage runs at the higher end of the range, I was seeing the current drop below 48a.

But yes, I did get the HPWC because someone else paid for 1/2 and also I figure it will last much longer running it much below the max operating point.

But I personally didn't ever see current fluctuations with the EVSE during the 9 months I used it.

 

[vystrcil]

I use the UMC and it gives me 29 miles per hour of charging. The HPWC, to me, isn't work the extra $500 for an extra 5 miles per hour (on a 75/75D). However...I will get one through the referal program soon, and will install it. Currently I am using a 3d print I found online for the UMC and cable.

Tesla3

• vystrcil
• Dec 11, 2017

Tesla2

• vystrcil
• Dec 11, 2017

Tesla1

• vystrcil
• Dec 11, 2017

 

[isjka]

Well I bit the bullet and decided to go with the upgraded 125 amp sub-panel in the garage. It made more sense and the installer knocked off $200 for me. We connected it yesterday and sure enough, I was getting the 35 miles per hour charge that the manual stated I would get based off the 60 amp.

 

[AnilSomani]

I iust picked up my Model-X a week ago.

Any recommended electrician's in orange county, CA? I am in cypress.

Thanks,
Anil