Am I overthinking charging?

[ericscottf]

Hi all,

I've got my MS coming "by the end of Sept". I'm an engineer, and keen to tinker/maximize the convenience, efficiency and cost of charging.

A few things I've been pondering:

1) If I get a time of use meter for my electric, my overnight charge rate is "fantastically" low (less than half daytime rate @ 0.19/kwh). I still have to figure out if it's economical, as my family stay home during the day, AC on fairly high, so the increase in daytime rate may offset the overnight decrease in cost....
From what I understand, you can't (yet) program the MS to be plugged in but not charge until a certain time of day.
Is it workable to install a timer based/internet connected switch to control the power to the charger, or does the car get upset if it is plugged in with no power/power turns on and off regardless of the car's expectations?
If not, I'd set something up where power turns on to the outlet after the rate goes down & also has the ability to be locally overridden by switch and also anywhere by internet connection.

2) I'm wondering if a small charge time with a partial fill on the car is at all frowned upon. Do I need to be cognizant of coming home, plugging in to charge, realizing I need to go out 20 minutes later, unplugging after only a small top up, running the errand, returning and plugging back in?

3) If #1 is OK, and the car is plugged in but has no power because the outlet is off, will it still recognize the plug and prevent the driver from ripping a (non powered) plug out of the wall/port? I'm assuming that if it's powered, the car will definitely alert the user...

Or am I overthinking all of this?

Thanks!

 

[murphyS90D]

You can program the car to start charging at whatever time you want.
You can stop charging and drive whenever you want, assuming you have enough charge to complete the trip.

 

[TaoJones]

Hi all,

I've got my MS coming "by the end of Sept". I'm an engineer, and keen to tinker/maximize the convenience, efficiency and cost of charging.

A few things I've been pondering:

1) If I get a time of use meter for my electric, my overnight charge rate is "fantastically" low (less than half daytime rate @ 0.19/kwh). I still have to figure out if it's economical, as my family stay home during the day, AC on fairly high, so the increase in daytime rate may offset the overnight decrease in cost....
From what I understand, you can't (yet) program the MS to be plugged in but not charge until a certain time of day.
Is it workable to install a timer based/internet connected switch to control the power to the charger, or does the car get upset if it is plugged in with no power/power turns on and off regardless of the car's expectations?
If not, I'd set something up where power turns on to the outlet after the rate goes down & also has the ability to be locally overridden by switch and also anywhere by internet connection.

2) I'm wondering if a small charge time with a partial fill on the car is at all frowned upon. Do I need to be cognizant of coming home, plugging in to charge, realizing I need to go out 20 minutes later, unplugging after only a small top up, running the errand, returning and plugging back in?

3) If #1 is OK, and the car is plugged in but has no power because the outlet is off, will it still recognize the plug and prevent the driver from ripping a (non powered) plug out of the wall/port? I'm assuming that if it's powered, the car will definitely alert the user...

Or am I overthinking all of this?

Thanks!

Yes, but far better to overthink than to underthink for sure.

You're fine with #2 and the car won't let you go anywhere if you're plugged in, so that takes care of #3.

 

[ericscottf]

Just to clarify for #3, if the car is plugged in, but the receptacle were dead... The car still prevents movement?

All moot if Murphy's comment is correct, that I can program the car to only charge at the optimal time as part of a schedule.

Thanks again
Eric

 

[chillaban]

#3: I would expect it to detect the connection regardless of electric power.

I've got a broken J1772 plug in my apartment complex that occasionally refuses to deliver power. Whenever that happens it reads 0V and says "check wall power" on the IC display but still refuses to let you drive.

 

[Caboom]

if you have your car plugged the car won't move it detects the cable.
i wouldn't spend the extra cash on having a 2nd meter installed. i have been charging between 12AM and 7AM for years it's a no brainer.

 

[roblab]

While you're overthinking, ponder one future scenario: You buy a few solar panels and install them instead of a meter. Then you opt for solar billing, instead of time-of-use EV billing. Then you buy a few more solar panels to celebrate not using all that gasoline. Then a few more to celebrate not having to do service on your car. You offset what you use to drive, and then offset what you use for living. The savings offset your cost of solar panels. Within a half dozen years or so, ALL your electricity becomes free, free for driving, free for living. The power company pays you when you make more than you use.

Think ahead a little farther than a couple months. Or further. But don't plan to pay for power the rest of your life when the sun shines free.

 

[ericscottf]

Oh, I'm eager for solar. My parents did theirs a few years ago, I'm looking forward to charging at their house and running my car off the sun. They run a net positive, feeding into the grid over the course of a year.
If solar ever became practical for my home, I would do it. Problem now is that I don't have enough roof area pointed towards the sun to take enough power out to make it worthwhile.
I'm sure that "once" the efficiency of reasonably priced later-gen consumer grade panels goes up another 20-30%, it'll be worth it for me

 

[AndreSF]

If solar is not practical for you at this time, I would look also into powerwall system. Combined with TOE EV plan rates, it could be quite lucrative in terms of filling up the battery at night and using that power during the peak times (A/C, other normal home use).

 

[DCGOO]

Hi all,

1) If I get a time of use meter for my electric, my overnight charge rate is "fantastically" low (less than half daytime rate @ 0.19/kwh). I still have to figure out if it's economical, as my family stay home during the day, AC on fairly high, so the increase in daytime rate may offset the overnight decrease in cost....

Is .19 the 24 hour rate, the TOU peak, or TOU off peak? All sound exhorbitant to me. Standard 24hour rate for me is less than .10. Including access, taxes and fees. Local utility has a TOU plan, but it is not even close to being compelling.

From what I understand, you can't (yet) program the MS to be plugged in but not charge until a certain time of day.
Is it workable to install a timer based/internet connected switch to control the power to the charger, or does the car get upset if it is plugged in with no power/power turns on and off regardless of the car's expectations?
If not, I'd set something up where power turns on to the outlet after the rate goes down & also has the ability to be locally overridden by switch and also anywhere by internet connection.

Not true. You can schedule the charge on all Teslas.

2) I'm wondering if a small charge time with a partial fill on the car is at all frowned upon. Do I need to be cognizant of coming home, plugging in to charge, realizing I need to go out 20 minutes later, unplugging after only a small top up, running the errand, returning and plugging back in?

There is no requirement to "fill up" the car. You can stop and start at any time.

3) If #1 is OK, and the car is plugged in but has no power because the outlet is off, will it still recognize the plug and prevent the driver from ripping a (non powered) plug out of the wall/port? I'm assuming that if it's powered, the car will definitely alert the user...

If anything is plugged in the charging port, powered or not, you cannot move the car. The Tesla app on your smartphone will (can) notify you when charging starts, concludes or is interrupted for any reason.

Or am I overthinking all of this?

Probably. But it is perfectly normal and expected. We've all been there.

 

[Ashkenaz]

You can also use app on phone and remotely start or stop charging as well as set limit of your charge. You can do this all from your phone.

 

[Dithermaster]

We have a separate meter on the EVSE (aka "charger") because we were in a DOE-funded charging study from when I had a Volt. We're not on a Time-of-Use (TOU) plan but they tracked our usage and told us what we would have paid had we been on one. The house use was break-even. So without changing our power usage patterns we would not pay more or less money for that electricity. I had set the Volt to only charge at night when the rate would be lower on TOU as my own experiment to see if I could live with that - I could. With that, the car charging would save us $100 per year to be on TOU. When I got the Model S I did not set it for night charging and we haven't switch to TOU (because it's hardly cheaper for us), but if the incentive gets better I might, and I could live with night-only charging with my commute, but only if I swapped my existing slow 240VAC 15A EVSE for something faster (at least 40A if not higher).

 

[AndreSF]

I could live with night-only charging with my commute, but only if I swapped my existing slow 240VAC 15A EVSE for something faster (at least 40A if not higher).

How long is your daily commute? Mine is 40 - 50 miles, and the car is always re-charged in the morning using Voltec 15Amp device (~9-10mph of rated charge gain). I'm using TOU and charging does not start until 11PM

 

[Dithermaster]

How long is your daily commute?

Quite short; just under 10 miles round-trip if I don't drive for lunch or have errands. 240/15 is more than enough for that, and TOU would be just fine, as it was (simulated) with the Volt. Heck, I survived for a week on UMC 120/12 when my Voltec 240V EVSE broke and I didn't have time to fix it.

My biggest concern about switching to TOU with only the 240/15 is that every now and then we take long trips, come home low, and sometimes have another long trip right after that, and I'd have to charge on the TOU high rate. I suppose worst case there is a Supercharger 10 miles away, so with just 10 miles range I can go anywhere! It just seems like $100/year is not much savings to offset the inconvenience of charging anytime I want.

 

[ElectricTundra]

TOU would have cost us a lot more. One or both of us is home most days and we have a number of computers and stuff going. Compliments of computers our house is heat positive so we never need heat unless below about 50f outside. The converse is that when we need A/C we need A/C. If outside is below about 75-80f and there's a bit of breeze we'll cool via windows but otherwise the meter is spinning pretty good. We do have a two-stage A/C.

Many days I don't drive more than 20-30 miles so not an extreme amount of daily charging.

I'd second the suggestion to consider investing in solar rather than TOU. We're looking at Sunslate for our house unless Tesla/Solarcity come up with something considerably better.

 

[AndreSF]

I suppose worst case there is a Supercharger 10 miles away, so with just 10 miles range I can go anywhere! It just seems like $100/year is not much savings to offset the inconvenience of charging anytime I want.

Exactly! Superchargers will support your long distance travel. Switching or not to TOU is obviously quite personal and depends on other uses during peak times. Combined with solar and potentially powerwall, it could be a part of an "earning system" though Sell high, buy low scenario.

 

[WannabeOwner]

program the MS to be plugged in but not charge until a certain time of day.

My home "charging schedule" is set (by geo-location) to start charging at 1am (when my off-peak rate starts); if I go out to a good party!! and get home at 2AM it still starts charging (not sure how long the "permitted late arrival" is, but I've seen people complain that it is "too long"). When I get to work, no geo-location-schedule set there, it starts charging straight away.

If I get home and want to charge immediately I can override the wait-for-1AM (its a one-time thing, so reverts to off-peak charging next time).

if a small charge time with a partial fill on the car is at all frowned upon

Departure for work is around 5:30, and the car is not always fully charged (i.e. to the 90% max-charge that I have set). I don't worry about it. Sometimes I only charge for a half-hour at home (10 miles range, or so) because I have to go out again but want to top up. Also, every time I use regen brakes I put a little bit back ... so I guess its OK ...

no power because the outlet is off, will it still recognize the plug and prevent the driver from ripping a (non powered) plug out of the wall/port?

The charge cable is locked into the car (until you press something [key fob, dashboard control, phone APP or, if you have one, the button on the car-end of the charge cable]) to release it. My home charger is a tethered cable, so cannot be unplugged at the house-end, for a non-tethered cable I don't know if releasing it [during charge, or if power is off] is possible.

 

[TexasEV]

Anyone who asks "Am I overthinking charging?" the answer is yes without even hearing more of the question. Just plug it in when you get home each evening, as you would your smartphone. Unplug it in the morning when you leave. Let the battery management system manage the battery.

 

[Sir Guacamolaf]

Hi all,

I've got my MS coming "by the end of Sept". I'm an engineer, and keen to tinker/maximize the convenience, efficiency and cost of charging.

A few things I've been pondering:

1) If I get a time of use meter for my electric, my overnight charge rate is "fantastically" low (less than half daytime rate @ 0.19/kwh). I still have to figure out if it's economical, as my family stay home during the day, AC on fairly high, so the increase in daytime rate may offset the overnight decrease in cost....
From what I understand, you can't (yet) program the MS to be plugged in but not charge until a certain time of day.
Is it workable to install a timer based/internet connected switch to control the power to the charger, or does the car get upset if it is plugged in with no power/power turns on and off regardless of the car's expectations?
If not, I'd set something up where power turns on to the outlet after the rate goes down & also has the ability to be locally overridden by switch and also anywhere by internet connection.

2) I'm wondering if a small charge time with a partial fill on the car is at all frowned upon. Do I need to be cognizant of coming home, plugging in to charge, realizing I need to go out 20 minutes later, unplugging after only a small top up, running the errand, returning and plugging back in?

3) If #1 is OK, and the car is plugged in but has no power because the outlet is off, will it still recognize the plug and prevent the driver from ripping a (non powered) plug out of the wall/port? I'm assuming that if it's powered, the car will definitely alert the user...

Or am I overthinking all of this?

Thanks!

#1 - You can set your MS to start charging after XX time, it's a very simple setting.
#2 - Not frowned upon at all, when you get home, just plug in.
#3 - Yeah that's ok. When the outlet comes on, the MS will start pulling power. The only thing you'll loose if your charge cable is not powered is, you won't be able to hit the button to open the charge port on the car. So you just hit the button on the car itself (the left portion of the charge port is a button), and you plug in the charger cable, and forget about it. When the power comes on, and the time is > what you set in #1, the car will start charging itself. One more thing - if you need to remove an unpowered charge cable, you'll need to "unlock port" from the Model S or the app.

 

[CmdrThor]

If solar is not practical for you at this time, I would look also into powerwall system. Combined with TOE EV plan rates, it could be quite lucrative in terms of filling up the battery at night and using that power during the peak times (A/C, other normal home use).

Without solar the Powerwall is not lucrative at all just trying to arbitrage TOU rates. Several articles were written after the introduction of the Powerwall:

The Economics Of Tesla's PowerWall Don’t Make Sense For Most Customers In North America | Zero Hedge