Tesla won't charge with mobile charger

[samchops]

Hi Everyone!

So a few days ago I got home after driving to charge my car and I immediately went to charge my car. It was around -6F weather the last few days (in Colorado) and I had around 25 miles remaining on my car. My mobile charger is plugged into standard outlook only pulling in 110V and it hasn't been an issue charging in this weather in the past. The next day around 16 hours later, I checked my car and it drained the battery all the way to 0%. Usually it would at least keep the charge and I've never seen it drain while being plugged in.

I left in the charger for a couple of days and noticed it was trying to heat the car battery and swap between charging at 4mi/hr to warming the battery. It was also doing odd things like whenever I opened the car door, the charging would stop and start blinking red with the error: BMS_a174. I figured the temp was too cold to heat the battery and charge the car so I'd wait until the temp increased. I put a service request in and the center seemed to agree with that theory. At this time, the app showed 0mi/hr and no message showing it was heating the car battery.

Today the temp increased to 40F and I unplugged and plugged the charger back and it showed that it was warming the battery again. I ran the cabin heater in my car for a while to get it to warm up and the message for warming the battery went away and then it finally showed 4mi/hr charging. It's been showing that consistently for the last 3 hours, but the battery still shows as 0% and no miles have been added.

Any thoughts on what could be causing this? Is the battery just super dead and needs time? Could the mobile charger just be busted? Is there an issue with the charge port?

Thanks in advance!

 

[Cosmacelf]

Well, first you have a circuit problem because the car is only drawing 8A instead of 12A. Just that alone would cause your issues because 8A would only warm the battery, not charge it. So try a different receptacle. You need to be drawing 12A for you to have a hope.

in general, using 120V for charging in a cold environment is not recommended. Get a 240V charging set up.

 

[samchops]

Well, first you have a circuit problem because the car is only drawing 8A instead of 12A. Just that alone would cause your issues because 8A would only warm the battery, not charge it. So try a different receptacle. You need to be drawing 12A for you to have a hope.

in general, using 120V for charging in a cold environment is not recommended. Get a 240V charging set up.

It jumps from 8-12/12A. I’ve seen this before in the past and didn’t have any issues on other chilly days. I wasn’t aware it’s supposed to stay at 12A. I’m definitely getting a higher circuit installed soon.

 

[Tronguy]

Ah. 120 VAC, the Mobile Charger, and Cold Temps. As they say, "That's your (triple-whammy) problem."

First off: Maximum power you're going to get out of a 120 VAC Mobile Charger, when hooked up to a bog-standard, 15A, NEMA5-15 connector, is 12A at 120VAC = 1.440W.

The problem with this: When it's seriously cold out, before the battery can charge, it has to be warm enough to take a charge. Now, you did the Right Thing by immediately connecting to your (presumably still warm) car when you got to your destination. However, it can take up to few kW (it varies, depending upon how cold it is) to get the battery up to temperature when it's, say, 20F out. But you're sitting at -6F. Um. I take a $RANDOM bet and say that, with the TMC in place, the car is losing more heat due to thermal conduction/radiation than it's getting from the battery warmer/act of being charged; when it gets cold enough, it switches to warming the battery up (a good idea, would like not to damage said battery) rather than charging.

If, in spite of all this, the battery temperature keeps on getting colder, then Charging Is Not What You're Going To Get.

My SO, when taking our 2018 M3 (which didn't have a heat pump, a heat pump being an artifact that helps these matters, to some extent) down to Maryland one frosty winter, discovered that, when plugging the car into the 120VAC outlet in her friend's garage, was getting somewhere between 0 and 1 mile of charge per hour. At home, in the warm, the same TMC would give 5 or 6 miles of charge per hour, so, well, one can see the effect of cold temperatures.

And this is why, if one is going to charge one's car in the cold, a 240 VAC outlet with some oomph is a Right Good Idea. A 32A connection at 240VAC gives one 7.68kW - and that's enough to get the battery warm and keep it there while charging.

Finally: In a Forum Far, Far, Away (Actually, the Tesla Forums, before they got shut down) we had this Science Teacher from Minot, North Dakota, who was buying a new Tesla (probably the first for a hundred miles around) and wanted to know about Charging. He was renting an apartment in a house. At the time, no Superchargers, or even public chargers, were anywhere near his place. And it was quickly pointed out that the winters in Minot were Other, and he really needed 240 VAC.

Turns out that his landlord was amenable and put in a NEMA14-50 outlet; I think we heard from him later, and his High School students were Impressed.

Sorry: But to fix your problem, you need More Power, Scotty!

 

[Tam]

...Any thoughts on what could be causing this?...

As everyone explained, the cause is that 120V is too weak to do both the warming and charging in cold weather.

120V in a hot region works because it doesn't need to warm the battery up, and it then has only 1 task: charging, not heating.

There's nothing wrong with your car and the mobile connector.

I hope you get 240V soon. Good luck!

 

[DanCar]

My Model Y started drawing 8 amps after a software update instead of 12 amps. I swapped mobile charges and Model Y went back to 12 amps. There seems to be a different between newer and older mobile chargers.

 

[shahryaran]

If the main hub of your garage is shared with other neighbors, your rates drops from 12 and that's not enough to earn up the battery and make it ready for charge.

 

[Tronguy]

Yeah-forgot to talk about the 8A issue.

The car checks the voltage before it starts charging, the monitors the voltage when the current steps up.

Now, if the voltage more than “yea” as the current heads up, then that’s an indicator of high resistance between the breaker box and the car. Most obvious reason for this would be a loose connection somewhere. If this is happening at some connection, there will be a lot of heat at that spot. And now we’re talking the danger of an electrical house fire and, no, I’m not joking.

The car’s rigged so that when something like this happens, it drops the charging current by some largish amount. Since the power dissipated in a loose connection goes as the square of the current, going from 12A to 8A reduces the dissipation by (8/12)^2, or by 2.5 times. Thus Saving the Day.

It crosses my mind that if you did, literally, have a screw loose, cold weather isn’t helping matters any, which is likely why you saw the current drop.

It’s also been noted that charging current will be reduced with a cold battery; I’ve seen that with Superchargers, but never on much lower power AC charging. So, dunno whether it’s a loose connection or an extra cold battery.

Oh, yeah: if one tries to charge a Tesla with a TMC and a garden-variety extension cord, said extension cord, even with “Heavy Duty” plastered all over it, typically has thinnish conductors with higher resistance than the 14Ga or 12Ga that’s in the walls by code. That makes for a voltage drop, the extension cord gets warm, and the Tesla will drop the current, fearing house fires.

The solution, if you’re dead set on using an extension cord, is to not get anything from Home Depot. I’ve had good luck at Harbor Freight where they sell extension cords for contractors. And, if the cord on that display says 15A, it means it. It’ll be more expensive than Home Depot, and the long ones really expensive, since one needs big gauge wire to carry that current and copper is expensive.

The only thing “Heavy Duty” about the Home Depot stuff is the thickness of the plastic.. and plastic’s less expensive than copper.

 

[stopcrazypp]

Hi Everyone!

So a few days ago I got home after driving to charge my car and I immediately went to charge my car. It was around -6F weather the last few days (in Colorado) and I had around 25 miles remaining on my car. My mobile charger is plugged into standard outlook only pulling in 110V and it hasn't been an issue charging in this weather in the past. The next day around 16 hours later, I checked my car and it drained the battery all the way to 0%. Usually it would at least keep the charge and I've never seen it drain while being plugged in.

I left in the charger for a couple of days and noticed it was trying to heat the car battery and swap between charging at 4mi/hr to warming the battery. It was also doing odd things like whenever I opened the car door, the charging would stop and start blinking red with the error: BMS_a174. I figured the temp was too cold to heat the battery and charge the car so I'd wait until the temp increased. I put a service request in and the center seemed to agree with that theory. At this time, the app showed 0mi/hr and no message showing it was heating the car battery.

Today the temp increased to 40F and I unplugged and plugged the charger back and it showed that it was warming the battery again. I ran the cabin heater in my car for a while to get it to warm up and the message for warming the battery went away and then it finally showed 4mi/hr charging. It's been showing that consistently for the last 3 hours, but the battery still shows as 0% and no miles have been added.

View attachment 1009536

Any thoughts on what could be causing this? Is the battery just super dead and needs time? Could the mobile charger just be busted? Is there an issue with the charge port?

Thanks in advance!

This is a frequently reported problem with 120V charging in the cold. It provides so little power that power taken up trying to get the car warm enough to charge is more than the 120V outlet can provide. If it is cold enough, the car actually drains battery instead of charging, as you found out.

If you have a garage, it would help to warm it up. If you have a space heater, that might help too.

I'm not entirely sure if running the cabin heater really helps you, as the battery pack is what needs to warm up.

Try to get a 240V option installed as soon as possible. If you have an electric dryer, using that port may work in a pinch. If you have a NEMA 5-20A outlet, that might also help squeeze a little bit more power, although you need the Tesla 5-20 adapter.

 

[Eric33432]

He did say it was a Ridgid brand brand extension cord, and that it is 10 gauge, which even though sold at Home Depot is a pretty good brand.

But you could have a problem with a high resistance where it plugs in to the outlet, or if the wire is a long run of #14 gauge that could also cause the voltage to drop too much.

Hope you can get a 240 volt NEMA 30 or 50 amp outlet installed soon, or better yet, a Tesla Wall Connector.

 

[KenC]

I haven't thought about 120v charging in so long. I ski, and the mountain I go to has 2 Tesla L2 chargers, nice, but it also has 2 120v outlets. The big advantage is that the chargers are near the main ski lift, so you can park close when the parking attendants are sending everyone to a remote parking lot, where you need to take a bus to get to the slopes.

I always see non-Teslas plugged into these 120v outlets, what exactly is the benefit if you're only plugged in for a few hours? And, they share an outlet!?! I guess the benefit of parking near the main lift is worth it, but it's still hard to imagine there's any actual electrical benefit to share a 120v outlet!

 

[DuncanM]

It jumps from 8-12/12A. I’ve seen this before in the past and didn’t have any issues on other chilly days. I wasn’t aware it’s supposed to stay at 12A. I’m definitely getting a higher circuit installed soon.

It could be a faulty outlet and it's worth changing it. If that outlet is fed with a 20amp breaker and 12-2 wire, then you could change the outlet to a NEMA 5-20 and (with the appropriate adapter cable for the TMC) you can charge at 16a/120v (get a high quality outlet). Alternately, if the outlet has a dedicated breaker (no other loads on the circuit) and is fed with 12-2 wire it might be possible to change the breaker to a 20amp 240v and the outlet to a NEMA 6-20 to allow charging at 16A/240v. If you have 14-2 wire then use a 15amp 240v breaker and a NEMA 6-15 outlet; You can then charge at 12a/240v. You will need the appropriate adapter cables for the TMC.

 

[Unclepaul]

120v barely has enough push to slowly charge up a warm battery. Not really enough to both warm it and charge it in frigid conditions.

Need 240v or Supercharger to really handle sub zero temps.

You might be able to get a little charging, but as the temps drop you might not be even able to maintain.

 

[Tam]

I always see non-Teslas plugged into these 120v outlets, what exactly is the benefit if you're only plugged in for a few hours? And, they share an outlet!?! I guess the benefit of parking near the main lift is worth it, but it's still h

120V is better than 0V. Tesla advises plugging in when not driving. If there's a choice between 0V and 120V, I would pick 120V.

It might not gain any miles but can keep the battery warm.

 

[Tam]

...Supercharger to really handle sub zero temps...

Someone said the software has fixed this problem:

The supercharger doesn't charge your car or charge too slowly to be perceptible when the battery is cold. Those who arrived at Chicago station had plenty of batteries waiting in line, like 30%, but as the heater warms up the battery, the SOC goes down. It then become too low to heat the battery up anymore. By the time plugging in, the battery is cold. It might take many hours of cold Supercharger to gain any miles.

In that case, strangely enough, plugging in with a 240V charger can gain more initial miles than a Supercharger can.

 

[milford@autobo]

Ah. 120 VAC, the Mobile Charger, and Cold Temps. As they say, "That's your (triple-whammy) problem."

First off: Maximum power you're going to get out of a 120 VAC Mobile Charger, when hooked up to a bog-standard, 15A, NEMA5-15 connector, is 12A at 120VAC = 1.440W.

The problem with this: When it's seriously cold out, before the battery can charge, it has to be warm enough to take a charge. Now, you did the Right Thing by immediately connecting to your (presumably still warm) car when you got to your destination. However, it can take up to few kW (it varies, depending upon how cold it is) to get the battery up to temperature when it's, say, 20F out. But you're sitting at -6F. Um. I take a $RANDOM bet and say that, with the TMC in place, the car is losing more heat due to thermal conduction/radiation than it's getting from the battery warmer/act of being charged; when it gets cold enough, it switches to warming the battery up (a good idea, would like not to damage said battery) rather than charging.

If, in spite of all this, the battery temperature keeps on getting colder, then Charging Is Not What You're Going To Get.

My SO, when taking our 2018 M3 (which didn't have a heat pump, a heat pump being an artifact that helps these matters, to some extent) down to Maryland one frosty winter, discovered that, when plugging the car into the 120VAC outlet in her friend's garage, was getting somewhere between 0 and 1 mile of charge per hour. At home, in the warm, the same TMC would give 5 or 6 miles of charge per hour, so, well, one can see the effect of cold temperatures.

And this is why, if one is going to charge one's car in the cold, a 240 VAC outlet with some oomph is a Right Good Idea. A 32A connection at 240VAC gives one 7.68kW - and that's enough to get the battery warm and keep it there while charging.

Finally: In a Forum Far, Far, Away (Actually, the Tesla Forums, before they got shut down) we had this Science Teacher from Minot, North Dakota, who was buying a new Tesla (probably the first for a hundred miles around) and wanted to know about Charging. He was renting an apartment in a house. At the time, no Superchargers, or even public chargers, were anywhere near his place. And it was quickly pointed out that the winters in Minot were Other, and he really needed 240 VAC.

Turns out that his landlord was amenable and put in a NEMA14-50 outlet; I think we heard from him later, and his High School students were Impressed.

Sorry: But to fix your problem, you need More Power, Scotty!

take a look at a device called a Quick220 power supply. u need 2 seperate 120 volt/60/1 phase outlets from your breaker panel . this will increase your charging and battery heating . do not turn on the cabin heater when on low voltage 120 circuit/15 amp power using the mobile connector

 

[Tronguy]

take a look at a device called a Quick220 power supply. u need 2 seperate 120 volt/60/1 phase outlets from your breaker panel . this will increase your charging and battery heating . do not turn on the cabin heater when on low voltage 120 circuit/15 amp power using the mobile connector

Actually, "Two separate 120 60Hz single phase" is more or less the definition of a split-phase 240 VAC circuit.

So, let's take this one piece at a time.. and maybe why the Quick 220 is Not Such A Great Idea.

So, first, what the heck is split phase? Answer: Down from ye power pole comes three wires.

• One thick wire, named neutral. In the US/Canada that goes through the meter on the ground lug and to the ground/neutral bus bar inside the breaker box. As an aside: A nice, thick wire from that bus bar goes right back outside of the house and it connected to a six-foot copper stake-in-the-ground (no kidding, I've seen an electrician with a hammer pounding one in.). So, when people say, "ground", yeah, they're really talking about the Ground.
• One thick wire that, for this discussion, we're going to call A. This goes to the next lug on the meter and goes from the output side to the "A" bus bar in the breaker panel. This bus bar goes to Every Other Breaker Socket in the breaker box.
• One final thick wire that we're going to call B. This goes to the final lug on the meter and goes from the output of the meter to the "B" bus bar in the breaker panel. This bus bar goes to the Rest Of The Breaker Sockets in the breaker box.

Get out an oscilloscope. Connect a probe to the A bus bar. You'll get a sine wave whose RMS value (as measured on a voltmeter) is 120VAC. Sixty cycles per second in the US/Canada.

Take another probe. While displaying the first probe on the screen, connect the second probe to the "B" bus bar. You'll see another sine wave. But, when compared to the first sine wave, it's inverted: When the "A" sine wave is going up, the B sine wave is going down.

Watch carefully. A voltmeter from A to ground/neutral will measure 120 VAC. A voltmeter from B to ground/neutral will also measure 120 VAC. But, if you place the voltmeter between the A and B bus bars, you'll get double the voltage, 240 VAC.

So, you want lights and standard outlets? A single-width breaker gets clipped into a slot in the breaker box, thus picking up the A or B bus, depending upon which slot one picked. A wire is attached to the other end of the breaker, then that "hot" wire, and a wire from the ground/neutral bus bar, is sent off to the lights/sockets/whatever that are 120 VAC. Current flows on the hot wire and the same current, coming back from the load, flows on the neutral wire. The accompanying green wire (people always use green for ground) carries no current.

Suppose you want to power up a 240 VAC load? You run out to your local electrical supply store and get a double-wide, ganged breaker. This gets plugged into two adjacent slots in the breaker box. There are two wires coming off the breakers with 240 VAC between them. Those two wires, maybe the neutral, and usually the ground (a total of 4 wires max) get sent off to the load. If you look at your random breaker box, there'll be a couple-three 240 VAC breakers, identifiable since they're double wide and ganged, in that box for things like the HVAC compressor, maybe the blower, and definitely for any electric ovens or electric clothes driers.

Let's talk about that 'ganged' bit. Say one has a 20A 240VAC circuit. The two breakers, one on each hot (A or B) are each 20A. So, yeah, if the load itself draws, say, 30A, both breakers are a-gonna go "Oh No!" and both pop open.

But let's get pernicious, like the Real World. Say some piece of plastic somewhere gets aged, or has a manufacturing defect, or some piece of metal goes Sproing! and breaks and Hits Something. So, the current on Phase A might be the usual 5A - but the current in Phase B, and ground and/or neutral, suddenly goes to 50A. One of those breakers in the breaker box goes "Whoops!" and pops open - and drags the other breaker, on Phase A, open. Thus saving the day from house fires. And I AM NOT JOKING ABOUT THE HOUSE FIRES.

So.. 240 VAC breakers are truly duly ganged for a Very Serious Reason: Keeping the occupants of the building Alive.

So, back to that Quick220 device. Sure: Walk into a $RANDOM room, play guess-and-by-golly with the sockets in that room, and one has a pretty good chance of finding two sockets that happen to be on two different breakers on two different bus bars back at the breaker panel. And the difference in voltage between the hots on those two sockets will be 240 VAC. (This is, by the way, the reason one never jimmies up an extension cord to connect to two different sockets. That way madness and loud POPS! lie.) And one may even power up a Tesla that wants a 240 VAC source at, say, 12A, and get 2880W of charging that way.

But the whole blame point about breakers is to Save the Blinking Day, and Messing With That Function Is How To Put Oneself and One's Nearest And Dearests int the hospital with burns over a significant portion of their bodies at 2 a.m.. Assuming that those involved survive. A short on one hot will pop one breaker, but it won't pop the other.

So, don't use that thing. Wire up a real 240 VAC circuit: That's what electricians do. A typical install for something like this is around $500 for the wiring, another $500 for the hardware. It's worth it.

Last thing. I spent the last 15 years or so of my career being either to go-to guy, or one of the go-to guys who would get dead, busted, smoked (no kidding) equipment back from the field, then figuring out what died, and trying to arrange things to THAT didn't happen again. Some of it was stuff like dead teeny capacitors or suchlike; some of it was bad designs, or bad installations, or scruffy parts, or counterfeit parts. But a certain amount of it was power related and, yeah, burnt holes in backplanes and such was something I had to work with. Usually associated with lightning, but you get the idea. Fundamental truth: There's No Such Thing As A Part That Never Fails. As engineers, it was our job to design with that fact in mind and keep the public safe. Having had to pick up the burnt remains from time to time, one really believes in safety standards and Not Violating Same. Just like the cop who's pulled One More Body Not Wearing A Seat Belt out of a car has very, very little sympathy for those people who think Seat Belts Are Not For Them.

 

[davewill]

So, back to that Quick220 device. Sure: Walk into a $RANDOM room, play guess-and-by-golly with the sockets in that room, and one has a pretty good chance of finding two sockets that happen to be on two different breakers on two different bus bars back at the breaker panel. And the difference in voltage between the hots on those two sockets will be 240 VAC. (This is, by the way, the reason one never jimmies up an extension cord to connect to two different sockets. That way madness and loud POPS! lie.) And one may even power up a Tesla that wants a 240 VAC source at, say, 12A, and get 2880W of charging that way.

But the whole blame point about breakers is to Save the Blinking Day, and Messing With That Function Is How To Put Oneself and One's Nearest And Dearests int the hospital with burns over a significant portion of their bodies at 2 a.m.. Assuming that those involved survive. A short on one hot will pop one breaker, but it won't pop the other.

So, don't use that thing. Wire up a real 240 VAC circuit: That's what electricians do. A typical install for something like this is around $500 for the wiring, another $500 for the hardware. It's worth it.

I don't actually disagree with you, but...

The real Quick220 device is designed to deenergize the 240v socket if both phases are not there. So if you pop one breaker, the other circuit is disconnected. If you're going to do it, use the real device. Besides in this era of GFI on all outdoor and garage circuits, you likely can't use it anyway.

The downsides you don't mention are people tripping over extra extension cords they end up using to find those two outlets; loose, aging outlets; the difficulty of finding two outlets that don't have significant loads on them and the poor state of wiring that often exists on your average 120v circuit.

So, by all means, put in a real 240v circuit, folks.

 

[BigNick]

Actually, "Two separate 120 60Hz single phase" is more or less the definition of a split-phase 240 VAC circuit.

So, let's take this one piece at a time.. and maybe why the Quick 220 is Not Such A Great Idea.

So, first, what the heck is split phase? Answer: Down from ye power pole comes three wires.

• One thick wire, named neutral. In the US/Canada that goes through the meter on the ground lug and to the ground/neutral bus bar inside the breaker box. As an aside: A nice, thick wire from that bus bar goes right back outside of the house and it connected to a six-foot copper stake-in-the-ground (no kidding, I've seen an electrician with a hammer pounding one in.). So, when people say, "ground", yeah, they're really talking about the Ground.
• One thick wire that, for this discussion, we're going to call A. This goes to the next lug on the meter and goes from the output side to the "A" bus bar in the breaker panel. This bus bar goes to Every Other Breaker Socket in the breaker box.
• One final thick wire that we're going to call B. This goes to the final lug on the meter and goes from the output of the meter to the "B" bus bar in the breaker panel. This bus bar goes to the Rest Of The Breaker Sockets in the breaker box.

Get out an oscilloscope. Connect a probe to the A bus bar. You'll get a sine wave whose RMS value (as measured on a voltmeter) is 120VAC. Sixty cycles per second in the US/Canada.

Take another probe. While displaying the first probe on the screen, connect the second probe to the "B" bus bar. You'll see another sine wave. But, when compared to the first sine wave, it's inverted: When the "A" sine wave is going up, the B sine wave is going down.

Watch carefully. A voltmeter from A to ground/neutral will measure 120 VAC. A voltmeter from B to ground/neutral will also measure 120 VAC. But, if you place the voltmeter between the A and B bus bars, you'll get double the voltage, 240 VAC.

So, you want lights and standard outlets? A single-width breaker gets clipped into a slot in the breaker box, thus picking up the A or B bus, depending upon which slot one picked. A wire is attached to the other end of the breaker, then that "hot" wire, and a wire from the ground/neutral bus bar, is sent off to the lights/sockets/whatever that are 120 VAC. Current flows on the hot wire and the same current, coming back from the load, flows on the neutral wire. The accompanying green wire (people always use green for ground) carries no current.

Suppose you want to power up a 240 VAC load? You run out to your local electrical supply store and get a double-wide, ganged breaker. This gets plugged into two adjacent slots in the breaker box. There are two wires coming off the breakers with 240 VAC between them. Those two wires, maybe the neutral, and usually the ground (a total of 4 wires max) get sent off to the load. If you look at your random breaker box, there'll be a couple-three 240 VAC breakers, identifiable since they're double wide and ganged, in that box for things like the HVAC compressor, maybe the blower, and definitely for any electric ovens or electric clothes driers.

Let's talk about that 'ganged' bit. Say one has a 20A 240VAC circuit. The two breakers, one on each hot (A or B) are each 20A. So, yeah, if the load itself draws, say, 30A, both breakers are a-gonna go "Oh No!" and both pop open.

But let's get pernicious, like the Real World. Say some piece of plastic somewhere gets aged, or has a manufacturing defect, or some piece of metal goes Sproing! and breaks and Hits Something. So, the current on Phase A might be the usual 5A - but the current in Phase B, and ground and/or neutral, suddenly goes to 50A. One of those breakers in the breaker box goes "Whoops!" and pops open - and drags the other breaker, on Phase A, open. Thus saving the day from house fires. And I AM NOT JOKING ABOUT THE HOUSE FIRES.

So.. 240 VAC breakers are truly duly ganged for a Very Serious Reason: Keeping the occupants of the building Alive.

So, back to that Quick220 device. Sure: Walk into a $RANDOM room, play guess-and-by-golly with the sockets in that room, and one has a pretty good chance of finding two sockets that happen to be on two different breakers on two different bus bars back at the breaker panel. And the difference in voltage between the hots on those two sockets will be 240 VAC. (This is, by the way, the reason one never jimmies up an extension cord to connect to two different sockets. That way madness and loud POPS! lie.) And one may even power up a Tesla that wants a 240 VAC source at, say, 12A, and get 2880W of charging that way.

But the whole blame point about breakers is to Save the Blinking Day, and Messing With That Function Is How To Put Oneself and One's Nearest And Dearests int the hospital with burns over a significant portion of their bodies at 2 a.m.. Assuming that those involved survive. A short on one hot will pop one breaker, but it won't pop the other.

So, don't use that thing. Wire up a real 240 VAC circuit: That's what electricians do. A typical install for something like this is around $500 for the wiring, another $500 for the hardware. It's worth it.

Last thing. I spent the last 15 years or so of my career being either to go-to guy, or one of the go-to guys who would get dead, busted, smoked (no kidding) equipment back from the field, then figuring out what died, and trying to arrange things to THAT didn't happen again. Some of it was stuff like dead teeny capacitors or suchlike; some of it was bad designs, or bad installations, or scruffy parts, or counterfeit parts. But a certain amount of it was power related and, yeah, burnt holes in backplanes and such was something I had to work with. Usually associated with lightning, but you get the idea. Fundamental truth: There's No Such Thing As A Part That Never Fails. As engineers, it was our job to design with that fact in mind and keep the public safe. Having had to pick up the burnt remains from time to time, one really believes in safety standards and Not Violating Same. Just like the cop who's pulled One More Body Not Wearing A Seat Belt out of a car has very, very little sympathy for those people who think Seat Belts Are Not For Them.

I learned something today.

 

[Cosmacelf]

I don't actually disagree with you, but...

The real Quick220 device is designed to deenergize the 240v socket if both phases are not there. So if you pop one breaker, the other circuit is disconnected. If you're going to do it, use the real device. Besides in this era of GFI on all outdoor and garage circuits, you likely can't use it anyway.

The downsides you don't mention are people tripping over extra extension cords they end up using to find those two outlets; loose, aging outlets; the difficulty of finding two outlets that don't have significant loads on them and the poor state of wiring that often exists on your average 120v circuit.

So, by all means, put in a real 240v circuit, folks.

Yes. I’ve tried to use Quick240 devices in the past and they usually don’t work. Major hassle finding non GFCI circuits on opposite phases. In this era of ubiquitous Superchargers, it just isn’t worth it to save 20 minutes at a Supercharger.