NEMA 14-50 Meltdown

[JPP]

I will definitely be using the better brand if I add another outlet but for now one charger thats hardwired works fine for both our cars

I know you hardwired and am glad. FWIW I have 2 of the original Elon Mush black Wall Connectors mounted with NEMA 14-50 pigtails. I don't unplug them and have upgraded the NEMA 14-50R in 2018, since the electricians originally installed them in 2013.

I dropped the comment about the better NEMA 14-50R only to inform readers who might not search these forums. Good electricians might select the $10 receptacle if they know the application is for a kitchen range or clothes dryer that do not pull 40A continuously for hours, or are not subject to repeated unplug-plug in cycles. But for EV charging, and where you might be using a Mobile Connector and unplugging and plugging it in, you want a heavy duty receptacle with really good wire clamping (not just a screw against the wire) to handle continuous 40A.

 

[PWlakewood]

I know you hardwired and am glad. FWIW I have 2 of the original Elon Mush black Wall Connectors mounted with NEMA 14-50 pigtails. I don't unplug them and have upgraded the NEMA 14-50R in 2018, since the electricians originally installed them in 2013.

I dropped the comment about the better NEMA 14-50R only to inform readers who might not search these forums. Good electricians might select the $10 receptacle if they know the application is for a kitchen range or clothes dryer that do not pull 40A continuously for hours, or are not subject to repeated unplug-plug in cycles. But for EV charging, and where you might be using a Mobile Connector and unplugging and plugging it in, you want a heavy duty receptacle with really good wire clamping (not just a screw against the wire) to handle continuous 40A.

Agreed but I only unplugged it a handful of times over the years so it shouldn't be wore out from that. Probably just a quality thing which I won't make that mistake again

 

[beatle]

For those with melted connectors, did any of you see a voltage drop while charging? I'd think if the wires were heating up due to resistance, the voltage would sag with the additional draw needed to maintain the same number of amps.

My anecdotal "evidence" so far is an inexpensive 14-50 from Home Depot and ~45 ft of 6awg wire. Voltage is still 243v for the duration of the charge, even at 40A for 7 hours. My UMC has only been unplugged twice, and it is supported in a wall-mounted bracket so there is very little strain on the plug/receptacle.

 

[TSLA Pilot]

Just curious--why is the OP (and others?) charging at 40 amps?

We leave our cars set at about 10 to 15 amps for most charging and have had zero problems with 9 MS's and two NEMA 14-50 (self-installed from Lowes/HD) since 2013.

Not only does lower amperage help avoid voltage sag, but it also reduces your heat waste, it is also likely better for the battery too.

FYI.

 

[ucmndd]

Just curious--why is the OP (and others?) charging at 40 amps?

We leave our cars set at about 10 to 15 amps for most charging and have had zero problems with 9 MS's and two NEMA 14-50 (self-installed from Lowes/HD) since 2013.

Not only does lower amperage help avoid voltage sag, but it also reduces your heat waste, it is also likely better for the battery too.

FYI.

RE "better for the battery", with a 100kwh battery we're talking about charging rates ranging from 0.024 C (10 amps at 240V) to 0.096 C (40 amps at 240V), so the difference from the battery's perspective is completely negligible.

Better for pretty much everything else, perhaps most importantly safety, I'd tend to agree. Pre-COVID I was driving 120 miles a day and set my gen 1 UMC to 30 amps, only increasing it on the rare occasion I needed a quicker turnaround. That was still plenty fast enough to charge completely and well within my off-peak TOU hours overnight.

 

[beatle]

I leave my charger at 40A but only charge my car to 75%. If I have a trip that warrants a higher SoC, I can easily bump the charge up in a short amount of time. If charging at 10-15A, that would take a lot longer.

If Tesla offered the ability to change amps from the app or API, charging at a lower amperage on the regular would be more popular.

 

[Rocky_H]

@TSLA Pilot I gave you a like for everything except the last thing. Yeah, I have the 40A capability, but I leave it set at 31A because I don't need my charging cable running that warm or that extra charging speed. But to think that the difference between 5 or 10 kW makes any difference to the battery is ludicrous. It can do over 100kW, so this dinking around with home charging rates is unnoticeable to the battery.

I leave my charger at 40A but only charge my car to 75%. If I have a trip that warrants a higher SoC, I can easily bump the charge up in a short amount of time. If charging at 10-15A, that would take a lot longer.

If Tesla offered the ability to change amps from the app or API, charging at a lower amperage on the regular would be more popular.

A. You don't have to go as low as 10-15A.
B. So what's wrong with just keeping it down a little lower in the car's setting? You can turn it down a few amps once and leave it. You don't need to tinker with it every day through the app.

 

[TSLA Pilot]

RE "better for the battery", with a 100kwh battery we're talking about charging rates ranging from 0.024 C (10 amps at 240V) to 0.096 C (40 amps at 240V), so the difference from the battery's perspective is completely negligible.

Better for pretty much everything else, perhaps most importantly safety, I'd tend to agree. Pre-COVID I was driving 120 miles a day and set my gen 1 UMC to 30 amps, only increasing it on the rare occasion I needed a quicker turnaround. That was still plenty fast enough to charge completely and well within my off-peak TOU hours overnight.

@TSLA Pilot I gave you a like for everything except the last thing. Yeah, I have the 40A capability, but I leave it set at 31A because I don't need my charging cable running that warm or that extra charging speed. But to think that the difference between 5 or 10 kW makes any difference to the battery is ludicrous. It can do over 100kW, so this dinking around with home charging rates is unnoticeable to the battery.


A. You don't have to go as low as 10-15A.
B. So what's wrong with just keeping it down a little lower in the car's setting? You can turn it down a few amps once and leave it. You don't need to tinker with it every day through the app.

Well, perhaps it's a climate thing.

Here in our Texas garage the cars' HVAC systems WILL kick in at higher than 10 or 15 amps of charge rate. This is not only a gross waste electricity and needless wear and tear on the car's HVAC system, but it also heats up the garage up even further; it is entirely useless for our use case of only a few miles a day. Even a 10 mph charge rate will give us a full 80 miles of range in an 8-hour overnight charge.

Heck, we only charge once or twice a week as the 100 kWh battery pack is pretty large, frankly.

The energy loss equation only counts the amps (amps squared, actually) so bringing the amps down as low as you can get away with is a very good thing.

In our case, with two MS's, and a not-small house, our electric bill is under $30 FOR THE YEAR thanks to our solar panels and efficient charging

(Side benefit: leaving a more usable planet for others to enjoy after we're worm bait . . . .)

TL;DR: Charge at the lowest amperage possible. Period.

 

[MP3Mike]

The energy loss equation only counts the amps (amps squared, actually) so bringing the amps down as low as you can get away with is a very good thing.

Of course there is the other side of efficiency as well. Charging at a higher rate is more efficient, though probably not significantly more. Since there is the base draw where the first x amps of charging are "thrown away" on keeping the car awake, pumps running, etc. (WK057 did a study on the Model S chargers in the past to find the most efficient charge rate.)

 

[beatle]

I actually found 32A to be slightly more efficient than 40A, but only by a few percentage points.

 

[PWlakewood]

For those with melted connectors, did any of you see a voltage drop while charging? I'd think if the wires were heating up due to resistance, the voltage would sag with the additional draw needed to maintain the same number of amps.

My anecdotal "evidence" so far is an inexpensive 14-50 from Home Depot and ~45 ft of 6awg wire. Voltage is still 243v for the duration of the charge, even at 40A for 7 hours. My UMC has only been unplugged twice, and it is supported in a wall-mounted bracket so there is very little strain on the plug/receptacle.

I never saw any voltage drops at all. 247 to 250 is normal for me.

 

[TSLA Pilot]

Of course there is the other side of efficiency as well. Charging at a higher rate is more efficient, though probably not significantly more. Since there is the base draw where the first x amps of charging are "thrown away" on keeping the car awake, pumps running, etc. (WK057 did a study on the Model S chargers in the past to find the most efficient charge rate.)

Don't know if WK057's work on this is still applicable.

At our low charge amperage I don't hear any pumps running, unlike with our earlier MS's.

Wish Tesla would provide more insider info on this.