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What charger(s) do I want/need for 2023 MY or M3?
- Thread starter mknmike
- Start date
So I just went nuts trying to figure out what I actually pay for electricity, and remembered it being around $0.20, which is similar to a $0.19/kWh chargepoint. I was right. BUT... I see that about 1/3 of my total electric bill is a $6.433 charge for the previous month's max hourly usage. A max kW use "Transmission Capacity Charge". So in addition to the cost per kWh, there's a significant charge for max hourly draw. This means that there's significant benefit to having a charge schedule that is aware of the other usage on your system. For example, if I pulled 10 kWh in a single hour at some point in the last few days/weeks, there won't be any additional cost if I run it up to 9 kWh in a single hour. But if I'm starting a new month, and I've only drawn 2 kW at most, then the charger should know to try and keep it below that level. If the M3 RWD can charge at 32 amps on a 240 Volt circuit, that seems to be 7.68 kW that it could draw. That's significantly higher than my baseline of about 1 kWh/h. So there's clearly benefit to limiting the draw.
I wonder if you can limit the charge rate at varying times of day, and quickly override them if needed. I assume that's all on the car side of things, not the EVSE which is typically a dumb device as I understand it. How would the car possibly know what my max house usage was that month? I've run up to about 10 kW with two AC units with hi velocity air handlers, and two pool pumps, two refrigerators and a deep freezer. If I drop to 2 kW for the house after using 10 kW, the car could go nuts and charge at full rate. But if most of those items are running and I'm at 9 kW, I would probably not want it to charge at all.
Learning more every day it seems. This one was about my power bill.
EDIT: Well, it looks easy enough to manually set the max Amp draw.
I assume there's nothing that enables the tesla to know what other draw is occurring on your home. Hopefully I will learn that.
RTPEV
Active Member
Those demand charges only apply during on peak hours, so if you can charge your car exclusively during off peak, you don't need to worry. There are smart chargers and systems that are able to cut power if household draw exceeds a certain amount, but they are not yet mainstream (and thus economical) so it's just easier and cheaper to just make sure you only charge off peak (or if you do need to charge on peak to just be aware of other major power consumers in your house and curtail them.
Your car has no access to the rest of the house' energy usage. However, you could install HomeAssistant home monitor system and it could link to your car as well as remotely controllable thermostats (ecobee, for example) to know when the A/C units are running and could remotely adjust the Tesla charge rate however you would like. With a little extra hardware, HomeAssistant could monitor the entire house power usage as well, if you really needed to.
Once you have HomeAssistant and learn how to use it, you can do a lot of nifty automations for your house and car.
When my wife starts the double-wall-oven and the AC is on, I manually turn off the AC just because I hate the idea of the AC fighting the oven. I could see a scenario where the Tesla arrives home and needs a charge during the day. AC gets shut off. I never really worried about the pool pumps but since the robot pump can't run when the main pump isn't running, a huge spike is seen when the robot runs the first hour the whole pool pump runs. Now I see why there's a big benefit to only run the pumps at night. I hadn't realized this was part of my bill as I see no lower cost for off peak hours. However reducing the height of my spikes clearly makes a difference.
This sounds very cool, and other than SENSE, I've seen nothing that monitors the whole house. Also, I have no idea how you would alter the Tesla charge rate dynamically via API of some sort. It sounds like pretty easy math if all the info and APIs are there. I just have no idea how to do any of that (yet) with a Tesla.
I will have to research HomeAssistant. This looks like a starting point: Automation to dynamically adjust Tesla charge rate based on home power usage
RTPEV
Active Member
You don't necessarily need to have the car do it. You can have the EVSE do it. The EVSE advertises a max current draw (or power level if you prefer) and this can change dynamically throughout the charging session. Various smart EVSEs have varying levels of automation and capabilities (from at a minimum advertising a lower charge rate during peak hours, to more actively monitoring whole house consumption and solar panel production to maximize charging from solar and shaving demand peaks. The car will simply draw only what the EVSE tells it its allowed to do, so no smarts have to be built into the car itself. If you have a whole house battery, even better as you can use that to shave peaks.
That said, the APIs do exist to control the car's charging, and as you said below, there is a suggested algorithm. It would not be terribly difficult to implement this, but I still think that the occasions where the car needs to be charged during on peak times are sufficiently infrequent that it can probably be managed manually (i.e. turn off high consumption devices while the car is charging).
Here are some other devices that are along the same lines:
SPAN® Panel | Lower your energy bill
SPAN Panel is a re-invention of the 100 yr old home electrical panel
www.span.io
This one is meant more for managing fleets and larger scale EV charging installations, but it does have the capability to monitor consumption. Way overkill for what you would need, but the technology exists.
Atom Power | Technology | Solid State Circuit Breaker
Atom Power revolutionized the circuit breaker by creating the world's first commercial UL-listed digital solid-state circuit breaker. With a solid-state circuit breaker, on/off control is intrinsic to the device. Once metering and communications are added, you have the perfect mechanism to...
www.atompower.com
This kind of device is meant to provide a hard limit whole house power consumption. I don't believe it can dynamically adjust power level (rather it just either turns the EVSE totally on or off), but it could at least provide a way to avoid mistakenly charging the car during on-peak hours.
DCC-10 | Charge controller for electric vehicles | RVE
The DCC-10 is an Electric Vehicle Energy Management System that allows a charger to be connected directly to an electrical panel at full capacity.
rve-usa.com
FYI there are gadgets you can plug into a 30A dryer plug that give 2 30A dryer plugs. The first plug gets power anytime whatever is plugged in demands power. The second plug only gets power if the first plug is doing nothing.
The downside is they cost about $300, so it is a substantial fraction of what it costs to get a new 30A circuit and plug (the other downside is "only" 30A not 50A).
I don't own one so I have no direct experience with them (two houses in row that didn't have a dryer plug in the garage).
I’ve got my plan for a dedicated outlet, and it won’t be hard. The urgency also just decreased a lot with Tesla taking away the $250 (down from $500. And now down to $0) referral code coupon and replacing it with 6 months of unlimited supercharging. There are 3 superchargers that are fairly convenient to me, but I am concerned about what supercharging does to the battery. It was something I was going to try to avoid, but now I will probably be tempted to use it often.
RTPEV
Active Member
Don't sweat it too much. While not ideal, it's also not a big deal as long as you aren't Supercharging multiple times a day every day.
That said, I have to say that even if I had unlimited Supercharging, the $1 or so a day that it would save me would still not be worth the reduced convenience of charging at home. When my wife had her ID.4, we had 3 years of free EA charging, and an EA charger just a few miles away, but we never actually went to use it.
It will make me more inclined to try and find a reason for a road trip though. Will that make me consider a larger or longer range Tesla? Nope. Still sticking with the smallest and cheapest.
First day of ownership I charged with a supercharger to 100% because I have the LFP battery. Also, 5 days after purchasing still don’t have my mobile connector. We are now below 47% with my wife running errands today. Some range anxiety is coming, as we are only at 145 miles and I left that supercharger at 100% with something like 82 miles on the odometer I believe. Lots of short trips, sentry mode, and preheating have been used, but from 272 miles remaining at 82 miles on the odometer to 47%/127 miles with 145 miles on the odometer (63 actual miles driven with 145 miles of battery used, ironically matches the odometer) seems like we certainly will not get the 127 miles remaining that we might expect. I guess you might derive from this that 145-63=82 miles of range is used for things other than driving after we supercharged to 100%
+ 24 hours to Thursday ~8pm
+ 24 hours to Friday ~8pm
+ 24 hours to Saturday ~8pm
+ 24 hours to Sunday ~8pm
+ 12 hours to Monday ~8am
———————————————-
~108 hours = 82 miles = 0.76 miles/hour burn rate with Sentry and preheating.
So it’s interesting to see that these things consume so much of the battery. I like the idea of being able to view videos of actions around the car. If someone was to damage the car, I certainly would want the video. Is it worth the electricity costs and CO generated from it? Probably not. There should be more efficient means of recording.
Anyway, it seems that a very low charge rate will be sufficient for the majority of our usage and lower charging rates, done off-peak should keep costs as low as possible and also be as courteous as possible for the electrical grid. I will probably limit charging to something like 16 amps and see how that goes once our mobile charger arrives. The 14-50 outlet is ready to go.
+ 24 hours to Thursday ~8pm
+ 24 hours to Friday ~8pm
+ 24 hours to Saturday ~8pm
+ 24 hours to Sunday ~8pm
+ 12 hours to Monday ~8am
———————————————-
~108 hours = 82 miles = 0.76 miles/hour burn rate with Sentry and preheating.
So it’s interesting to see that these things consume so much of the battery. I like the idea of being able to view videos of actions around the car. If someone was to damage the car, I certainly would want the video. Is it worth the electricity costs and CO generated from it? Probably not. There should be more efficient means of recording.
Anyway, it seems that a very low charge rate will be sufficient for the majority of our usage and lower charging rates, done off-peak should keep costs as low as possible and also be as courteous as possible for the electrical grid. I will probably limit charging to something like 16 amps and see how that goes once our mobile charger arrives. The 14-50 outlet is ready to go.
Moderator? I wish I could change the thread title of this one to include “RWD, SR”.
In any case, the only thing I feel I am lacking with my charger setup that I’ve currently (no pun intended) got setup is a cord hanger. For now, I’ve got a rubber belt hanging on a hook that takes just a bit of extra work to hang the cord. Otherwise, I don’t think there’s ANYTHING else that the wall charger would provide me with a M3RWD. I also really don’t want to charge over 32 amps due to the Peak Load Calculation portion of my power bill. 48 amps would just mean that portion of my bill would be 50% higher. No thanks. Very happy here. And I can take the charger with me on a trip if we were to ever take one. Maybe when my wife goes to the beach 100 miles away for a weekend or if we take a road trip. Otherwise it stays plugged into the NEMA 15-50 in the garage.
I’m glad I put the NEMA 14-50 on a board instead of mounting it directly to the wall. I was able to flip it over without opening it up when I realized the direction the Tesla cord goes. This was no bueno.
I still want to put the wire in conduit and maybe shorten it, and maybe add a cover to make sure dust and debris can’t get into the outlet now that the cord comes out the top. I’ve got it covered in duct tape for now.
In any case, the only thing I feel I am lacking with my charger setup that I’ve currently (no pun intended) got setup is a cord hanger. For now, I’ve got a rubber belt hanging on a hook that takes just a bit of extra work to hang the cord. Otherwise, I don’t think there’s ANYTHING else that the wall charger would provide me with a M3RWD. I also really don’t want to charge over 32 amps due to the Peak Load Calculation portion of my power bill. 48 amps would just mean that portion of my bill would be 50% higher. No thanks. Very happy here. And I can take the charger with me on a trip if we were to ever take one. Maybe when my wife goes to the beach 100 miles away for a weekend or if we take a road trip. Otherwise it stays plugged into the NEMA 15-50 in the garage.
I’m glad I put the NEMA 14-50 on a board instead of mounting it directly to the wall. I was able to flip it over without opening it up when I realized the direction the Tesla cord goes. This was no bueno.
I still want to put the wire in conduit and maybe shorten it, and maybe add a cover to make sure dust and debris can’t get into the outlet now that the cord comes out the top. I’ve got it covered in duct tape for now.
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