I could ignore charge scheduling glitches if I could turn on the charger's 14-30 outlet only at off-peak times. But I can't find any such devices. Is the current flow simply too high even for a relay?
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Why are There No 14-30 Outlet Timers?
- Thread starter PianoAl
- Start date
Here is a 240V 40A relay. It has a 120 Volt coil you can run with your 120V timer. It is 3 pole but you need only use 2. Put it all in a junction box.
These are very commonly used in A/C condenser units to power the compressor.
These are very commonly used in A/C condenser units to power the compressor.
ATPMSD
Active Member
Is this what you are looking for?
Um. You guys might want to think carefully about that relay/contactor.
There's this thing called a "snubber". It consists of a resistor of relatively low value in series with a high-voltage, typically film or ceramic capacitor (non-polar). Whenthe contacts open, any inductive load will result in a inductive kick that will cause an arc. (Think: Unplugging a running vacuum cleaner, and the flash seen in the wall socket when one does so.) One has to be careful about capacitors that go across power: There's X-rated and Y-rated caps, and Reasons one uses one or the other, the idea being not to cause a fire, or kill someone, when a capacitor fails.
That kick from an inductive load is fast, with fast rise times. So, in the snubber, the capacitor becomes, more or less, a dead short to that fast rise time, the energy in the inductive kick goes preferentially through the capacitor and into the series resistor, dissipating the inductive kick energy into the resistor. Rather than, say, causing an arc between the contactor contacts, causing the contacts on the contactor to turn silver into silver vapor and pitting the contacts.
My understanding is that snubbers make relay/contactor points last a lot longer.
Now, with a Tesla Wall Connector, when the charging session is over, the car stops drawing current, and it's then, and only then, that the contactor in the wall connector opens.
I ran into this whole business at work where, at an installation of some of the gear that I supported was in a location where Snubbers Weren't Used, causing all sorts of EMI and contactor problems. The customer had installed contactors sans snubbers on city power, since contactors bought that way were cheaper.
I haven't tried looking up contactors with and without snubbers; I'm not sure, but I think OEM contactors come both ways. I looked at one of the links and no snubbers were mentioned. I suspect that one can roll one's own (there's examples of the circuit on Wikipedia), but it would probably be best to get a UL-certified widget with the right components.
There's this thing called a "snubber". It consists of a resistor of relatively low value in series with a high-voltage, typically film or ceramic capacitor (non-polar). Whenthe contacts open, any inductive load will result in a inductive kick that will cause an arc. (Think: Unplugging a running vacuum cleaner, and the flash seen in the wall socket when one does so.) One has to be careful about capacitors that go across power: There's X-rated and Y-rated caps, and Reasons one uses one or the other, the idea being not to cause a fire, or kill someone, when a capacitor fails.
That kick from an inductive load is fast, with fast rise times. So, in the snubber, the capacitor becomes, more or less, a dead short to that fast rise time, the energy in the inductive kick goes preferentially through the capacitor and into the series resistor, dissipating the inductive kick energy into the resistor. Rather than, say, causing an arc between the contactor contacts, causing the contacts on the contactor to turn silver into silver vapor and pitting the contacts.
My understanding is that snubbers make relay/contactor points last a lot longer.
Now, with a Tesla Wall Connector, when the charging session is over, the car stops drawing current, and it's then, and only then, that the contactor in the wall connector opens.
I ran into this whole business at work where, at an installation of some of the gear that I supported was in a location where Snubbers Weren't Used, causing all sorts of EMI and contactor problems. The customer had installed contactors sans snubbers on city power, since contactors bought that way were cheaper.
I haven't tried looking up contactors with and without snubbers; I'm not sure, but I think OEM contactors come both ways. I looked at one of the links and no snubbers were mentioned. I suspect that one can roll one's own (there's examples of the circuit on Wikipedia), but it would probably be best to get a UL-certified widget with the right components.
Thanks, but any solution over $50 would probably not be worth it. So far the few glitches there have been have only wasted a few dollars each (for example a 29 kWh charge when the rate was 47 vs 17 cents per kWh).
If the button is pushed in the charging wand when the car is an actively charging, the car handshake signal is broken. The car stops pulling current AND the EVSE cuts the power. I’m not sure if the EVSE waits any time before opening the relays to cut the power.
But, it is important that the EVSE cuts power quickly so that the end of the charging wand isn’t live and exposed to fingers once it’s pulled out. So if there is a delay to save the relay contacts from arcing it would need to be pretty small.
Paino:
I feel like a Tessie fan boy on these forums sometimes, so let me apologize in advance. However: If you use a schedule, be it tesla's or the more flexible Tessie version, you can still use Tessie automation schedules. I too have had a few rare "misses" that have screwed me. For anything important I now set redundant commands via automations and spread them apart by 15-30 minutes. I've had no events were two commands went missing.
YMMV, and worth no more than you paid for it.
Right on all counts. But if I understand the OP's idea, he was going to enforce a charging schedule by popping the contactor at timed intervals.
That leaves pretty much Zero Time for the car to stop charging, thereby inducing arcing, for sure. With or without inductive kick one has a low-impedance path through the car and an teeny-tiny air gap on the contacts as the contactor opens up; depending upon where one is in the cycle of 60 Hz, one is going to get a little or a lot of arcing. Fun fact that many of you probably know: Once an arc is established, the ionized air is very low impedance and will support an arc for a longer period of time. What the snubber does is during the critical microseconds as the contacts are moving apart, any inductive kick (and there's always some) will raise the voltage across the contactor pins rather abruptly; the C-R of the snubber will limit and absorb the energy, thus allowing the arc to quench.
The snubber will reduce (not eliminate) the wear on the contacts.
By the by: I don't know about newer HVAC systems, but I would be surprised if there wasn't some kind of electronic switch that works much as a Tesla does and eliminate the current before the contactor contacts started to move. On ye old-timey furnaces/HVAC systems, when the blower fan gets turned off, it very definitely is Inductive Kick Time with that electric motor. I haven't worked much on these particular things, but I do remember that contactors can be bought with and without snubbers. And, of course, nothing says that the snubber has to be integral to the contactor; the snubber is just an R-C network across the contacts and can be placed anywhere, although it's better, of course, if the components are close.
I am confused by what you mean by "charge scheduling glitches"? Hard for me to imagine these would be regular enough to warrant spending a $100-200 (I'm guessing) to buy and install something to switch the outlet. I am guessing that some software solution might be better/cheaper. I know if you use TeslaFi.com you can turn on/off charging at times of day and someone above mention another third party website that I assume can do the same.
You're correct that most glitches are just a annoying, such as when it starts charging a half-hour before the off-peak time. The glitch that made me start thinking about a solution: The car started charging at 8 PM when it was set to depart at 9:45 AM. That has only happened once, but now I have to make an OCD check every night before I go to bed that it isn't charging.
If it happens again, I'll look into a software solution. I often see people report problems such as phantom drain or non-sleeping that are related to third-party apps. Is that overblown?
Thanks for making me understand why a hardware solution won't work.
Can someone recommend the simplest app for restricting charging that won't interfere with Tesla's app? I just want to say "Let the Tesla app control things, but only charge between midnight and 3 PM."
Thanks.
davewill
Active Member
You could try a small relay board wired into the pilot signal inside the wall connector. It would interrupt the pilot, which will keep the car from turning on the wall connector. They make them that connect to WiFi which would give you the ability to schedule it or remotely override it. It needs to be able to handle +/-12v. Here's an example:
You'll have to do your own research to make sure it will work for the application.
You'll have to do your own research to make sure it will work for the application.
Only need one. I'm asking which is the simplest one that will meet my need and not interfere with Tesla's app.
If you want a simple solution, why not just use the Tesla fixed start time and start charging 10 minutes after midnight or whatever your off peak start time is ?
This is the simplest solution, and does not require any third party apps to accomplish. It works perfectly, provided your home charging solution is fast enough to charge your car during off peak time.
I have been using scheduled charging (not scheduled departure) for years (literally years, like 3-4) and have not had a single problem / issue with it starting when its supposed to (not a single one).
The only thing that is a slight quirk but easily understandable (and also spelled out by Tesla in the manual somewhere) related to scheduled charging is the "If you plug in within 6 hours past the scheduled start time, the car will start charging" feature. I presume its there because you could have scheduled charging at 10pm but not get home till midnight (for example) and the car would start charging to ensure you got charged.
If you plug in more than 6 hours past the scheduled time , it waits till the next scheduled time.
I have my cars set to charge at 3am (for my 3) and 4am (for my wifes Y).
The only reason I can think of that people feel compelled to do scheduled departure vs scheduled charging is some sort of extra concern / worry about "gotta finish charging right before I leave". In places where its super cold or its imperative that the charging be done right before you leave to have a battery as warm as possible, I guess it makes sense for that, but for most people, scheduled charging is better, and without the quirks.
Second the point. The Tesla charging screen has two features that are a bit funky to get one's brain around: "Scheduled Charging" and "Scheduled Departure".
Frankly, I still have some trouble figuring out how to use these guys. What I usually wanted to do was, when I was commuting to work every day, was for the car to be Ready To Go and Warmed Up (especially in the winter) at some fixed time every morning.
One would think that setting a time for Scheduled Departure would do this thing, and it kind of does, but it's seemed to me to be mainly interested in getting the cabin temperature to the right value. So, put in a Scheduled Departure for 8 a.m. the following morning, plug the car into the Wall Connector at 5 p.m. the previous day, and it would start charging immediately.
On the other hand, putting in Scheduled Charging for, say, 1 a.m. (when the rates are cheap, say) and plug the car in at 5 p.m. and the car won't start charging until 1 a.m..
There's some kind of combination of the two settings that'll give one the best of both worlds: Given that, say, one is leaving for $DISTANT_DESTINATION at 9 a.m., it's possible, with the right settings on the car, for it to (a) look at its navel, figure out how long it's going to take to get to 100% charge, and start charging long enough in front of the departure time so it's done when one wants to leave and (b) to turn on the internal heat and such soon enough before one is leaving in this situation so the car's warmed up and ready to go.
I've managed to pull this off a few times, but I always forget the correct sequence of screen presses. The car's settings seem to imply that it's Scheduled Departure/Scheduled Charging, only, but there's tricks.
Exactly. And what makes it confusing is that one of those things is a charging scheduling function, and one of them is NOT. So why did Tesla place them both in the charging screen?
Yes, it's just a cabin HVAC scheduler.
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