I tricked my car charging station into powering a 7.5 kW heater
[ka-chunk] [CHONK - blower motor starts] No, that's not some special shop heater designed to work with electric car chargers, in fact it's an ordinary shop heater which I very-slightly modified so I can use my charging station to power it. And I did this for two reasons: One, to hopefully demonstrate in a way which is a little more intuitive than in my previous videos that these charging stations are nothing but slightly smart power cords (a fact which I'll explain more later on) and two: Because this is a product that I wanted and that I think should exist but it currently doesn't exist so I made one! However, my hacked-together version is missing a few key features which would make the product more useful and safer, so this should simply be viewed as a proof-of-concept. I understand the risks I’m taking here and this is definitely not ready for prime time as I built it. So don’t try this at home.
For those of you who might not know what these are, these are just really powerful forced-air electric heaters. That’s all. Here in the US, thanks to our weedy little plugs and relatively low household voltage, ordinary plug-in space heaters like this top out at 1,500W. Which is plenty of heat for even a fairly large room, assuming it’s well-insulated, but if you’re trying to warm up, say, a cold garage - it’s going to take a heater like this absolutely forever if it can even manage it. But this heater can pump out 7,500W of heat.
That’ll heat up the garage a whole heckuva lot faster, five times faster, in fact, which would be great since I’m about to do something of a garage reorganization project and I picked the exact wrong time of the year to do it. But there’s a problem: these things need a 240V circuit to operate, and usually that means hardwiring them. This unit doesn’t have a power cord at all - you’re expected to permanently mount it somewhere, run electrical conduit to one of these knock-outs and directly wire it to the appropriate circuit using the lugs in its electrical compartment. That’s quite a lot of work for a $150 electric heater which I’m only going to be using occasionally.
Portable high-powered shop heaters are available - here’s a nearly 5 kW model... but that presents the same issues. Yes, it has a power cord but it has a NEMA 6-30 plug on the end of it which, while receptacles for it do exist, are not common at all.
I don’t have one of those in my garage so that heater would be no use to me. Ah but as it happens I already have a hefty 240V circuit installed in my garage for my charging station. It feeds a NEMA 14-50 receptacle which powers the charging station itself. Now, in theory I could just buy a range cord like this and then wire it up to the heater. So long as this was long enough to reach the receptacle from where I want the heater to go, I could unplug my charging station from the wall and then plug in the heater whenever I want to use it. But that solution is kludgy - the cord hanging down right next to the other one would annoy me very muchly, but also (and most importantly) these chonky monster plugs are a right pain in the butt to use.
They are simply not designed for frequent plug insertion and removal. They’re also kind of terrifying. The plug on the other end of the charging station, though - that one was explicitly designed to be used regularly.
This is a J1772 connector which, I should note, is in the beginning stages of being superseded by the J3400 connector here in North America, a charging connector previously exclusive to Tesla cars. The change is mostly just physical: passive adapters which convert between those two plugs are already available. In fact, here’s the one that I keep in my car for AC charging. So the change is not a big deal - I’m only bringing it up because before too long this specific connector will stop being so common but the basic gist of this video would be exactly the same if I were using a J3400 AC charger. I would just be installing a different charge port on the heater. Anyway, the critically important thing to understand about electric car chargers like this is that… they are not battery chargers! These don’t do any power conversion or voltage regulation or anything like that.
This charging station simply checks to make sure things are safe and then uses a contactor inside the enclosure to energize the cable - with a nice loud clack. [CLACK] And that’s all it does! When that green light is on, the charging station is simply sending the 240V AC power that’s coming from the wall straight to the car, and the car itself does the necessary power handling to charge up its battery pack. Car charging was designed this way because the car’s battery pack could be any number of configurations. It might be a higher voltage than another car, or it might use a different battery chemistry - down the road it might even have a solid-state battery.
Creating vehicle charging infrastructure which is specific to a battery pack voltage and chemistry just doesn’t make any sense: it would keep becoming obsolete as better batteries appear. So we’ve never done that, we just give the car raw electricity. Now, I will note that DC fast charging - done by those really big chargers that look something like a gas pump and offer dozens or even hundreds of kilowatts of power output - that’s a whole other kettle of fish which is not relevant to this video.
But, if you’ll indulge me in making a rather important point that many people haven't seem to have figured out yet, DC fast charging *should* only ever be necessary for road trips. I rarely ever use those things because I can charge at home, and if policy makers had any idea what using an electric car is actually like, they’d be spending much more effort getting these cheap things installed anywhere people live and work with a major focus on apartment complexes and car-dependent places with street-parking only. Because once you know you are going to be able to charge your car where you park it, either overnight when you're asleep or during the workday when you're at work, you’re gonna stop worrying about how and where to charge it. Range anxiety just goes away.
And these things are cheap. They should be everywhere. But anyway, back to the topic at hand. Since this often-so-called-but-not-actually charger is really just a big, high-current power cable delivering 240V AC to an easy-to-use connector... it could do a lot more than just charge a car if we wanted. And I wanted! So I did. Which you saw at beginning.
And which I will explain nextly. But there’s one very important thing to make clear before we start: despite how simple these charging devices are on the surface, they are doing one very, very important extra thing as they deliver power to a car: they announce over one of these two control pins how large the charging circuit the car is now attached to actually is. Which is critical for the car to know as it charges up. This heater won't understand that which is a problem.
I’ll discuss the repercussions of that later in the part where I talk about all the pitfalls of what I’ve just done here, but for this project, I bought this model of heater knowing that its power requirements are matched to the power my charging circuit and this charging station can provide. The heater draws 31.3 amps max, and my charging station can supply 32 amps continuously. That means to power this heater with that charging station, all I need to do is wire a J1772 charging inlet up to the heater’s power input and then somehow trick the charging station into thinking it’s plugged into a car which is requesting to charge when I plug it into the heater. That will cause the charger to close its contactor and boom - the heater will have the power it needs. Actually I’m hoping there won’t be a boom but we’ll burn that bridge when we get to it.
First, let’s handle the easy parts. I need to get power wires hooked up to the charging inlet. These connectors are a little fiddly to disassemble but eventually you can remove the pins which, in this case, you’re expected to solder to directly. The three largest pins on the J1772 connector are, unsurprisingly, for handling the power: line 1, line 2, and a protective ground. Though the ground pin is slightly smaller so be sure to set it aside.
I will not pretend that I’m great at this, and given how large these wires and pins are I needed to use a butane torch to generate enough heat to melt the solder, but eventually I had all three power wires in-place and I could reassemble the connector. And just as a note - because this is going on a heater which will be indoors, I’m not bothering with the waterproofing components and that means that technically I haven't finished putting this together. But it’s together enough for my purposes.
Of course the connector needs to be mounted on the heater itself and we need to get those power wires into the electrical compartment somehow. There’s a lot of open area behind the fan so I decided to drill a hole for and mount the connector here and then I ran the wires to a second hole I drilled which leads down into to theelectrical compartment. And whaddya know, inside there the heater's got a lug for line 1 and line 2, and there's a bonding point for grounding the body of the heater. So… just connect those three wires up to where they need to go. I got fancy this time and used ferrules for the power wires.
And when it comes to those wires which goes where doesn’t matter: this is split-phase 240 so there is no neutral. I know, it’s weird! But of course the ground wire needs to go to the grounding lug. And, when it comes to the power connections, we’re done. That’s it.
Except, well right now if I plugged the charging cable into here, nothing would happen. The charging station won’t close its contactor and energize the cable unless a car signals it to do so. And luckily for us, that signaling scheme is incredibly simple! The charging station sends out a pulsing 12V signal on the control pilot pin, and when connected to a car, the car will shunt the control pilot pin to its chassis ground through a diode and a resistor. That causes a voltage drop on the signal pin which the charging station can measure. And, when the charging station sees the right thing, it will energize the cable.
I’m skipping over some details here but long story short: if I connect the control pilot pin to the heater’s ground through a diode and an 882 ohm resistor (or something close enough) the charging station should react as if a car is requesting power and thus it should close its contactor and energize the cable. And that’s why I also soldered this small wire to the control pilot pin - connecting it to the ground lug through that resistor and diode should be enough to trick the charging station. So, with that done it was time to test it out. OK, so if this worked when I plug it in the charger should show “charging” [clack] and it does.
The light is on so this should… just work. [clunk, blower starts] Pretty cool! That was quite easy. The most difficult part by far was figuring out where to mount the connector and cutting a hole for it.
Making the actual connections was fairly trivial. So now, all that’s left to do is hang this thing from the ceiling somewhere. This heater isn’t designed to be portable and it has some pretty specific mounting requirements so it should be installed permanently.
But a nice benefit of this setup is that I can mount this thing anywhere in my garage that my charging cord can reach. I decided to mount it close to the charging station just because that would be the most convenient spot, and with that done I’ve got a working shop heater! [clack] [CHONK] [hmmmmmm] Of course one downside here is that I can’t charge my car and use the heater at the same time but… I really don’t think I’m ever gonna want or need that. For a start, I only need to charge my car about once a week. And when that day rolls around, I wait to charge it until the dead of night when electricity is cheapest - in fact I have the car programmed to only charge between 11:30 PM and 5:00 AM.
So when I plug it in outside those hours it doesn’t actually start charging, instead it says “charging scheduled” and patiently waits until 11:30. If I’m not already asleep by then I will be soon and I’m not gonna keep the garage warm if I’m not out there actually doing something. And that’s really the point of this whole project! I have this high-powered, easy-to-use car charging thingamajig in my garage which only gets used about once a week. Why not make it useful for something else, too? And most importantly, this approach eliminates the need for running a new circuit and all the faff that entails - especially helpful for me since I only have 100A electrical service.
I would have a pretty hard time getting an electrician to sign off on adding another 40A circuit to my already pretty full panel without getting a service upgrade. And a heater which can be powered by a car charger becomes especially useful for those of you who have hard-wired car charging stations which can’t possibly be unplugged from the wall to use that circuit for something else. Of course using this heater is fairly expensive: it’s resistive electric heat, after all, and something slurping down 7.5 kilowatts costs me about one dollar per hour to use on average. But at the same time, this thing isn't gonna run constantly. If it’s extremely cold outside it might run for an hour or so when I first switch it on but after that point it’s gonna be cycling on and off as its thermostat regulates the room temperature, so the overall cost to use this won’t actually be any higher than if I let an ordinary space heater handle the job.
This level of power is all about getting the cold garage warm quickly, and it’s not actually necessary for maintaining a toasty warm temperature out there since it’s pretty well-insulated. Speaking of toasty warm garages, this heater also lets me illustrate one of the coolest things about the big batteries found in electric cars. When this thing is running, it’s pulling just about the same amount of power as my car does when it’s charging its battery pack. So after one hour of running nonstop, the heater consumes the same 7.5 kilowatt-hours that my car does after one hour of charging.
Running the heater for an hour makes the garage pretty warm! That much energy increased the room temperature from 54 degrees up to 78 degrees! (that’s about 12 to 26 Celsius) and that test was filmed at night when it was slightly below freezing outside. Yet, when the car charges up its battery for an hour, despite consuming the same amount of energy, the garage only warms up very slightly, barely enough to notice even after hours of charging. That’s because the vast majority of the energy my car takes from the wall isn’t released into the room as heat! Instead it’s stored as a chemical reaction inside its battery pack for use later. That process isn’t perfectly efficient, but it’s close - only a few hundred watts are lost when charging the battery cells, so only a few hundred watts of heat are released by the car when it's charging - even though it is in fact consuming the very same seven thousand five hundred watts that this giant heater does. And now that I have this thing which lets me feel just how hot 7.5 kilowatts of electricity actually is -
so hot that the air leaving the heater is over three hundred degrees Fahrenheit - I’ve got a pretty neat demonstration of how incredibly efficient electric car charging is. Batteries, turns out, are pretty cool. But now comes the part where I explain all of the ways what I’ve just done here is a bad idea. Remember when I said the charging station announces to the car how big the charging circuit is? Yeah, so this charger (along with every other AC charger out there) is modulating that 12V signal on the control pilot pin to tell the car it’s plugged into how many amps it is allowed to draw from the circuit. That needs to be communicated to the car because the car is the actual electrical load: this thing, as I hope you understand by now, is just a power cable and a switch, but charging circuits? They come in all sorts of sizes. I’m gonna skip over the weeds about continuous loads and the 80% rule here but the important part is an actual car will use the charger’s control pilot signal as a sort of speed limit and lower its charging current to match what it tells it.
For instance, my car can pull 48 amps to charge at over 11 kilowatts, however it knows when it’s plugged into this charging station that it’s only allowed to pull 32 amps. So that’s what it does, charging at about 7.5 kilowatts. This heater has no idea what that signal is and even if it did, it can’t lower its power draw to match the signal. For me in my garage with this heater and that charger, that’s no problem - I know this thing has a maximum current draw slightly below 32 amps. But if I were to, say, visit my parents with this thing [holy transition, batman!] well now it's a problem. Their charger, because it’s connected to a smaller circuit, is configured to tell any car plugged into it that it can only safely pull 24 amps which is about 5.5 kilowatts.
That is, for the record, more than plenty for charging a car overnight unless you’re a supercommuter but it’s not enough to power this heater. Yet the connector I bodged onto it will still signal their charger to close the contactor and supply power so the heater will still work. Which is bad. Now, if you haven’t already spotted it there is actually a power selector switch on this thing. This heater is made up of three 2.5 kilowatt heating elements and you can shut one of them off to turn it into a 5 kilowatt heater if you like. So if I do that - actually this is perfectly fine to use with this charging station.
But I could also turn the third element back on and… that would become a problem. The circuit would now be overloaded and the wiring would start heating up which is not good. The 30A circuit breaker protecting the 10 gauge wiring in this circuit should trip before things get too too spicy but we don’t want to be relying on that if we don’t have to. And it’s probably not enough to sell a high-powered device like this with a simple warning about circuit capacity.
If I were put in charge of designing something like this for sale (which for the record I’m not saying would be a smart idea!) I would give it the logic circuitry necessary to understand the J1772 capacity signaling protocol and I’d use three separate relays for its heating elements. Then, when plugged in it could determine how many of those heating elements could be switched on given the max current signal coming from the charger. That would allow the same product to work safely on any charging circuit, even a weedy little 12A, 2.8 kilowatt supply. That wouldn’t be a whole lot more heat than a standard space heater but 2.5 kilowatts is still a 66% bonus. Or, if more product skus is your jam and you want more models for sale rather than a one-size-fits-all heater, at the very least each one should have enough smarts to refuse to operate if it detects that it’s connected to a smaller charging circuit than it needs.
That’s not the only problem that would need to be tackled, though: there’s also the issue of electrical arcing. That’s a fairly small problem in the grand scheme and it’s not much of a safety issue, really, but it could potentially become one given enough time and misuse. When an actual car gets connected to a charging station like this, the contactor closes and energizes the cable before the car starts drawing any power from the circuit. Likewise, when the car is disconnected from the charger, pressing the latch on the handle [clicky clicky] it actuates a switch which signals to the car through the proximity pilot pin to stop pulling power, which it does almost instantly. Both of those actions ensure that no electrical connections are made or broken while under a load, and this prevents electrical arcing which damages electrical contacts over time. This heater, uh, well it’s not that smart.
It’s got no logic circuitry in there whatsoever: it’s just got a basic bimetallic thermostat (which also serves as the power switch), a high-temperature limit switch to shut it down if it’s overheating (as would happen quite quickly if the fan motor were to fail), and, uh well, a contactor of its own. As a side note, that contactor is actually pretty impressive for such a cheap and basic thing. It’s a three-pole contactor with each heating element getting its own set of switch contacts, so each contact is only switching about 10 amps despite being rated for 32 - enough for each one to switch the whole thing! That’s mighty impressive compared to the single-pole contactor in the central air conditioner we looked at a couple years ago.
And that thing’s gotta switch two big motors which makes for very sparky connections! I’m mildly annoyed this cheap heater got such a nice contactor. Anyway, if the thermostat’s switch is closed when you plug the heater in, then the moment the heater is supplied with 240V, it’s gonna start pulling power. In theory, that’s not actually a problem when plugging the heater in. Its contactor has to physically move the contacts inside of it in order to power the heating elements so there’s a small delay between when the contactor in the car charger closes and when that contactor closes. [Ka-clack!] That should mean any potential arcing is limited to the contactor inside of here, which is normal.
But if you unplugged the heater while it was running... well now we’re definitely gonna have an arcing problem. The button on the charge handle will not do anything, so the heater will keep drawing current as you remove the plug. And that could cause some nasty arcing on the charging connector contacts which could damage them and lead to overheating down the road. But the arcing could also happen inside the charging station. If, as you remove the plug, the control pilot pin lost connection before the power pins do, then the charging station will open its own contactor and de-energize the cable, cutting off power to the heater.
But that’s also not great - now the charging station has to interrupt the full 30-ish amps the heater is pulling and it’s not really designed for that. Some car chargers use the same sort of contactor that’s in the heater, but others (like this Grizzl-E charger or this cheap Amazon thing) use what are basically large relays which, while they can open under load, aren’t really expected to do that repeatedly. It’s really only for emergencies such as when the charger detects a fault and repeatedly breaking that much current could damage it with time. Now, the severity of that arcing problem is debatable. I may be making a big deal out of nothing, this is mostly a resistive electrical load after all.
But in any case there’s an easy solution: just turn the heater off before unplugging it and also never turn it on before plugging it in. Since I’m the one who put this together and I’m probably gonna be the only person to ever use it I’m reasonably sure those instructions will be followed but for a product sold to the general public, you can’t count on instructions like that alone. So for a real product, I would make sure it can detect the request-to-unplug signal coming from the latch button that way it can shut itself down as you reach to unplug it. Or at the very least I would add a mechanical interlock to the connector which prevents removal of the plug while the heater is running, and there are a whole bunch of potential ways to do that.
But whether an actual product like this could ever be sold is an open question. Obtaining safety certification for it would probably be a bit of a nightmare, and that’s assuming the Society of Automotive Engineers wouldn’t send you a nastygram demanding that you pull the product from the shelves for misusing one of their precious standards. Then again, if this 4,800 watt portable shop heater is a product for sale, it seems to me like the only real headache would be convincing… whoever needs convincing that products other-than-cars should be able to use a car charging station. And I think there’s a case to be made for that. One of the most annoying things about the North American electrical system is all these dang plugs.
Have you seen the Wikipedia article on NEMA connectors? Yeah there are simply way too many of them. They are cleverly designed to be physically incompatible that way you can’t put the wrong plug into the wrong hole but that means you’re pretty much only ever installing them for dedicated things like a dryer, a kitchen range, or a car charger. Meanwhile we came up with this much nicer-to-use high-current connector that supplies up to 80 amps and broadcasts how much current can safely be pulled from it and I feel like it would be a shame to only ever use this (or the J3400 connector) for electric vehicle charging. And, given what has happened with USB, it could easily be argued there’s already a precedent for this. But that’s all for now. Except, no, I forgot about one other thing.
While most home charging stations are simply delivering AC power, and that's probably still gonna be the general case for quite some time, vehicle-to-home and vehicle-to-grid technology has the potential to make this a little messier. Already there are electric vehicles for sale which can backfeed power through their charge port to provide emergency power, in fact my car can do that, though it’s a pretty basic function. Other vehicles offer the ability to provide backup power for your entire house, and right now those solutions are all pretty bespoke and hardly standardized.
But assuming we do create some sort of standard for that, which it seems like we will, home charging stations are going to get more complicated. What precisely that’s going to look like in the future is anything but clear. I have a feeling they’ll still provide the same basic functions as this charger, delivering straight 240 when asked, and any new features will be layered on top of that. Plus for backfeeding the grid, the vehicle could (in theory anyway) just backfeed AC through the same dumb charging station - it doesn’t care which direction the current is flowing. At least I don’t think it does.
But we already see some vehicles which are able to connect their battery packs to external devices and offload DC power - that’s how Ford’s Intelligent Backup Power works on the F-150 Lightning, and thanks to our split-phase power system where there’s a neutral wire the car’s usually not hooked up to, an external inverter is required for powering most of the stuff in your home when the power’s out. At least if you want to do it through the charge port. But that's a problem for future us. Now, this is actually the end of the video. I intend on keeping this car for many more years - it’s pretty much the perfect car for me and I have no reason to replace it. So this charging station is gonna hang around for a long while.
And even if I get a new car, so long as I haven’t moved I’m still gonna use this charging station! It might have a different charge port but you can just stick an adapter on the end of there and then it becomes a J3400 charger. So, whenever the day comes that I have a new car and I want to use this heater? I'll just take that adapter off and plug it in. And by the way, this 32 amp charging station is still massive, massive overkill for my needs! It completely charges my car from empty to full in 12 hours and the number of times I have actually needed to do that is zero. And if there were a second electric car in my household, I’m quite confident this single charger would take care of both.
You don’t need two chargers in two-car households unless both drivers are supercommuters. Like, more than 100 miles a day each. If you made it this far, this is probably just gonna be preaching to the choir but the reason I like electricity so much is that, in case you haven't noticed, it can do… ANYTHING. The very same wires that go into this electrical panel and are powering my lights, TV, stereo system, computer, smart speakers and pinball machines can charge my car to take me places, cook my food to have a meal and in myriad ways, preserve my food in the refrigerator, heat and cool my home to keep me comfortable, and now they can heat my garage, too.
Just imagine how much more work would have been involved running a gas line and venting for a gas-fired shop heater. And yes, my car is a little slower to charge when I’m on a road trip, but day-to-day I’m never stopping for gas on my way home from work or anywhere else. I just plug the car in and it charges while I sleep. Those of you who still refuse to see how awesome that is are really missing out. ♫ modificatedly smooth jazz ♫ No, that’s not some special shop heater designed to work with an electric car charger… [disappointed sighment] Seconds in and I flubbed a line Which is plenty of heat for even a fairly large room assoming it’s - assoming? Wow, this isn’t going great. But the basic gist of this video will be ex--- fraIdidaphetackbadadah Portable. Powered. Shop. Hi?
…exactly the same if I were using a J3400 AC charger. I would just be installing [bong as plug hits heater]… great work, me! So I did! Which you saw at the beginning. And which whyweeuvd….
oooops! I realized when I first tested the thing that I should have set "pretty hot!" rather than pretty cool. Oh well, no sense getting hot and bothered over it. Though maybe I should have said "the air coming out of this is so hot you could use it as an air fryer..." must. resist. executing. silly. idea.
2024-12-26 13:07
