charging model 3 in self powered mode without draining powerwalls?

[crackers8199]

i just had my powerwall install finished over the weekend, so i'm still stuck in self powered mode. until time based control and/or the vehicle charge limit settings show up in the app (which i plan to use for the most part i think), what's the best way for me to charge my car without completely draining the powerwalls insanely fast?

i see three options at the moment:

1) set reserve percentage to 100%...which is not optimal, because then i am drawing from the grid for everything, not just the car. right?

2) set the car to charge around noon, when i'm at peak solar (but before the batteries are completely full)

3) set the car to charge around 2:30pm, when my batteries should be full (today was the first real sunny day, and they got to full at almost exactly 2:30)

is there some other way to handle this that i'm missing? if not, which of these three options is the best / most cost effective? ideally i'd like to charge the car from the grid during off-peak or super off-peak times, but that doesn't seem possible at the moment...am i correct in thinking that this is the best way to handle charging once TBC is available, or are one of these (or another) more effective?

 

[jjrandorin]

There is not a tesla automated way to do that without taking yourself off grid. If you take yourself off grid, there is a setting (or will be a setting, the settings take a few days to show up), to allow car charging to drain the battery only X percent. That setting is only for "off grid" it does nothing when on the grid.

As far as whats "best", that depends on plan you are on. If you are on a time based plan, then you could use time based settings. I use self powered mode and just set my car to charge at like 3am. The car will quickly drain "whats left in my powerwalls down to the reserve", because charging your car with powerwall energy is like using AAA batteries to charge 2 D batteries.

Still, because I am still on a tiered rate plan, its best for me to use "as little as possible" from the utility. Most people are not still on this plan, and I am holding onto it for as long as they will let me.

 

[power.saver]

i just had my powerwall install finished over the weekend, so i'm still stuck in self powered mode. until time based control and/or the vehicle charge limit settings show up in the app (which i plan to use for the most part i think), what's the best way for me to charge my car without completely draining the powerwalls insanely fast?

i see three options at the moment:

1) set reserve percentage to 100%...which is not optimal, because then i am drawing from the grid for everything, not just the car. right?

2) set the car to charge around noon, when i'm at peak solar (but before the batteries are completely full)

3) set the car to charge around 2:30pm, when my batteries should be full (today was the first real sunny day, and they got to full at almost exactly 2:30)

is there some other way to handle this that i'm missing? if not, which of these three options is the best / most cost effective? ideally i'd like to charge the car from the grid during off-peak or super off-peak times, but that doesn't seem possible at the moment...am i correct in thinking that this is the best way to handle charging once TBC is available, or are one of these (or another) more effective?

You want to start charging just as the batteries get full, and set the charging rate (in the car) low so that is is about the same as the excess solar you would produce. That should minimize draw from the grid and keep the solar operating at capacity.

 

[crackers8199]

There is not a tesla automated way to do that without taking yourself off grid. If you take yourself off grid, there is a setting (or will be a setting, the settings take a few days to show up), to allow car charging to drain the battery only X percent. That setting is only for "off grid" it does nothing when on the grid.

As far as whats "best", that depends on plan you are on. If you are on a time based plan, then you could use time based settings. I use self powered mode and just set my car to charge at like 3am. The car will quickly drain "whats left in my powerwalls down to the reserve", because charging your car with powerwall energy is like using AAA batteries to charge 2 D batteries.

Still, because I am still on a tiered rate plan, its best for me to use "as little as possible" from the utility. Most people are not still on this plan, and I am holding onto it for as long as they will let me.

I'm on TOU PRIME. considering switching to 5-8 for the baseline credit (med baseline so a bit higher than the normal credit) but still need to do the numbers to see if that's worth it.

what do you have the reserve set at? I have mine at 10% right now but I have been all over the place while researching the best level the set that at...

 

[crackers8199]

You want to start charging just as the batteries get full, and set the charging rate (in the car) low so that is is about the same as the excess solar you would produce. That should minimize draw from the grid and keep the solar operating at capacity.

I guess I'll need to pay attention over the next few days... supposed to be full sun and hot (so will probably use some AC which we didn't use at all today).

 

[Tim-in-CA]

You want to start charging just as the batteries get full, and set the charging rate (in the car) low so that is is about the same as the excess solar you would produce. That should minimize draw from the grid and keep the solar operating at capacity.

This is the way unfortunately. When I do need to charge from home, I play the same game. Luckily you can adjust the charge rate of the vehicle on the fly from the app. Tesla has ALL THE DATA THEY NEED to do this automatically! It’s a PITA that this needs to be done manually. Because I’m not sure if the Rivian app (or any other future EV I may get) I installed a Wallbox Pulsar Plus charger that allows on the fly output adjustment from their app.

 

[jjrandorin]

I'm on TOU PRIME. considering switching to 5-8 for the baseline credit (med baseline so a bit higher than the normal credit) but still need to do the numbers to see if that's worth it.

what do you have the reserve set at? I have mine at 10% right now but I have been all over the place while researching the best level the set that at...

Its going to be hot the next few days here, probably a tad hotter where you are than where I am, but not much. March / April / and May are when you will normally make a large dent into your yearly totals, as, (in general) we get lots of production, and dont tend to have to use the AC much till starting in late may early june.

To answer your question, I have 2 powerwalls and I have the reserve set to 20%, however I try to stay off the grid as much as possible (tiered plan as I mentioned, not on TOU). Every time I looked into TOU, it was going to cost me $600 to $1000 more a year, even according to SCE. Anyway, what reserve to set it at depends on how often you think you might need to actually use it for a power outage, your hourly electrical usage in your home, what the weather is going to look like the next day, how big your PV system is, etc.

My reserve will be mostly 20% from now to about october, with the exception that I change the reserve manually if its going to rain, etc. I still enjoy
changing that manually, so have not looked into trying to automate anything (which would be more involved).

Since you are already on a TOU plan and cant go back, I would say that if I was on a TOU plan I would likely take 4-9 instead of prime or 5-8 but I am not on medical baseline.

 

[crackers8199]

Since you are already on a TOU plan and cant go back, I would say that if I was on a TOU plan I would likely take 4-9 instead of prime or 5-8 but I am not on medical baseline.

therein lies the rub: SGIP equity resiliency (w/ med baseline) requires me to either do prime or 5-8. 4-9 unfortunately is not an option.

ideally, i would make sure i'm sending any excess solar back to the grid during peak hours (either 4-9 on prime or 5-8 on the other option), to maximize my credits even though it won't be much, and use powerwall for the rest of the peak time. anxiously awaiting time based to show up in the app.

 

[crackers8199]

This is the way unfortunately. When I do need to charge from home, I play the same game. Luckily you can adjust the charge rate of the vehicle on the fly from the app. Tesla has ALL THE DATA THEY NEED to do this automatically! It’s a PITA that this needs to be done manually. Because I’m not sure if the Rivian app (or any other future EV I may get) I installed a Wallbox Pulsar Plus charger that allows on the fly output adjustment from their app.

this makes sense, but wouldn't this effectively be the same thing as just using the same strategy as @jjrandorin (set to charge around 3 or 4am and deplete the powerwalls to the reserve, then let solar charge them to 100% during the first half of the day)...this would cause them to export to the grid after getting to full, effectively offsetting most of what i would use from the grid to charge the car (after the powerwalls get down to the reserve).

am i misinterpreting that?

 

[Tim-in-CA]

this makes sense, but wouldn't this effectively be the same thing as just using the same strategy as @jjrandorin (set to charge around 3 or 4am and deplete the powerwalls to the reserve, then let solar charge them to 100% during the first half of the day)...this would cause them to export to the grid after getting to full, effectively offsetting most of what i would use from the grid to charge the car (after the powerwalls get down to the reserve).

am i misinterpreting that?

If you aren’t home during the day or have the time or patience to manage, I’d say that’s the best option. I try to avoid paying SCE any NBCs as much as I can!! It’s not a lot, it’s just principle! Lol!

 

[crackers8199]

If you aren’t home during the day or have the time or patience to manage, I’d say that’s the best option. I try to avoid paying SCE any NBCs as much as I can!! It’s not a lot, it’s just principle! Lol!

thankfully, i don't have to worry about NBCs. i'm on NEM 1.0 still.

 

[slcasner]

this makes sense, but wouldn't this effectively be the same thing as just using the same strategy as @jjrandorin (set to charge around 3 or 4am and deplete the powerwalls to the reserve, then let solar charge them to 100% during the first half of the day)...this would cause them to export to the grid after getting to full, effectively offsetting most of what i would use from the grid to charge the car (after the powerwalls get down to the reserve).

am i misinterpreting that?

This way the energy going into the car has gone into and back out of the Powerwalls which means 10% loss. It is best to use the excess solar directly into the car during the day if you are home and can manage the charge rate to consume most of the solar and just let a little bit go to the Powerwall. That's what I do (as a retired person). I found that I need to avoid letting the Powerwalls hit 100% because the solar then drops down to a lower level, even if the car is asking for all of it, until the Powerwalls discharge a little. This is with the Tesla inverter in a Powerwall+.

 

[crackers8199]

This way the energy going into the car has gone into and back out of the Powerwalls which means 10% loss. It is best to use the excess solar directly into the car during the day if you are home and can manage the charge rate to consume most of the solar and just let a little bit go to the Powerwall. That's what I do (as a retired person). I found that I need to avoid letting the Powerwalls hit 100% because the solar then drops down to a lower level, even if the car is asking for all of it, until the Powerwalls discharge a little. This is with the Tesla inverter in a Powerwall+.

i'm home all day since i work from home, but i don't have time to sit and manage the charge rate on the car constantly...ugh. seems like there should be a better way to do this...especially since my super off-peak time is right when the solar really starts cranking during the day (8am-4pm). ideally i would charge from the grid during that time and let all of the solar go to the powerwall...

also, i don't have powerwall+. just ordinary powerwall 2, if that matters.

 

[crackers8199]

so. TBC showed up early this morning and so far is doing what I want. I set the car to charge at 8am when super off peak starts, and it's currently charging and pulling everything from the grid while directing all solar to the powerwall.

will be interested to see what it does the rest of the day once the car is done charging. supposed to be very hot today, so there will likely be some A/C usage which hasn't been there the past two days except for overnight (I like it cold when sleeping)...

 

[slcasner]

i'm home all day since i work from home, but i don't have time to sit and manage the charge rate on the car constantly...ugh. seems like there should be a better way to do this...

I've seen a couple of posts about software to run on some computer to monitor the solar output and use the car API to adjust the charge current accordingly. I have not taken the time to work on this for myself yet. It is not necessary to adjust the charge rate to match the solar output unless the Powerwall is nearly full.

especially since my super off-peak time is right when the solar really starts cranking during the day (8am-4pm). ideally i would charge from the grid during that time and let all of the solar go to the powerwall...

If the powerwall needs the solar to fill up, then by all means, that's where the solar should go first. In my situation of not having PTO so I can't export the excess solar to the grid, I want to capture as much as I can in the car after the powerwall is nearly full. I say nearly full because if it hits 100% then it causes the solar inverter to reduce its output.

also, i don't have powerwall+. just ordinary powerwall 2, if that matters.

The significance of the powerwall+ is that means I have a Tesla solar inverter whose output level can be adjusted by the Gateway to match the house load once the battery is full (since I can't export the excess). I gather that you have existing solar, probably with some other manufacturer's inverter.

 

[crackers8199]

I've seen a couple of posts about software to run on some computer to monitor the solar output and use the car API to adjust the charge current accordingly. I have not taken the time to work on this for myself yet. It is not necessary to adjust the charge rate to match the solar output unless the Powerwall is nearly full.

If the powerwall needs the solar to fill up, then by all means, that's where the solar should go first. In my situation of not having PTO so I can't export the excess solar to the grid, I want to capture as much as I can in the car after the powerwall is nearly full. I say nearly full because if it hits 100% then it causes the solar inverter to reduce its output.

The significance of the powerwall+ is that means I have a Tesla solar inverter whose output level can be adjusted by the Gateway to match the house load once the battery is full (since I can't export the excess). I gather that you have existing solar, probably with some other manufacturer's inverter.

correct. existing sunpower system.

 

[crackers8199]

a little more of an update: time based control was working the way i wanted in that it was charging the car from the grid during off peak, but then was only discharging the powerwalls during the 4-9pm peak times and never using it any other time. i tweaked my TOU rate in the app to extend the peak time period to be from 3:30pm-2am, and set the car to charge at 2am...this has so far done exactly what i want. the car charges from the grid at 2am (which even though it's technically just off-peak and not super off-peak is the same rate at the moment), all (or at least most) solar is directed to the powerwalls in the morning (with the house pulling from the grid), and then once the batteries are full all (or most) solar goes to the grid. the solar i'm sending to the grid in the afternoon mostly offsets what i pulled from the grid in the AM. the powerwalls discharge starting at 3:30 and run down to either the reserve or until 2am, whichever comes first.

so far, i'm happy with this. we'll see how well it does next week when the temps are a bit more reasonable and i don't have to use as much AC...

 

[el-guapin]

If the PWs are set to full back up mode, they won’t discharge unless there is an outage. Why not do this on the days you will need to charge your EV (during the day)then change back the operating mode on PWs when finish charging?

 

[crackers8199]

If the PWs are set to full back up mode, they won’t discharge unless there is an outage. Why not do this on the days you will need to charge your EV (during the day)then change back the operating mode on PWs when finish charging?

that would work too, but i'm more looking for a way to automate it without having to worry about switching things back and forth myself. keeping it in TBC as i have it now seems to work pretty well.

 

[MY2uy]

a little more of an update: time based control was working the way i wanted in that it was charging the car from the grid during off peak, but then was only discharging the powerwalls during the 4-9pm peak times and never using it any other time. i tweaked my TOU rate in the app to extend the peak time period to be from 3:30pm-2am, and set the car to charge at 2am...this has so far done exactly what i want. the car charges from the grid at 2am (which even though it's technically just off-peak and not super off-peak is the same rate at the moment), all (or at least most) solar is directed to the powerwalls in the morning (with the house pulling from the grid), and then once the batteries are full all (or most) solar goes to the grid. the solar i'm sending to the grid in the afternoon mostly offsets what i pulled from the grid in the AM. the powerwalls discharge starting at 3:30 and run down to either the reserve or until 2am, whichever comes first.

so far, i'm happy with this. we'll see how well it does next week when the temps are a bit more reasonable and i don't have to use as much AC...

Hey there I would love if you private message me about doing all of this or post on here some more details. So what your saying is

8am - 330pm let solar and grid charge battery while powering house.

3:30pm - 2am let battery / grid power house (no charging)

2:00am charge the car at what rate?? The lower the rate, the longer it takes to charge. I have a tesla model y... I was thinking 32A? Should I set it to where car will depart by 7am?

So should I leave it on self supply or switch to cost savings? I'm thinking just leave it on self supply.