For those with solar and Powerwalls, I wrote this article that explains some easy ways you can get a little more effective power out of your system and increase Powerwall longevity. https://teslatap.com/articles/solar-powerwall-system-optimizations/
Yep. Avoid the PW round-trip and wear & tear.
Solar direct charging is the best way to charge an EV. I wrote a script that automates keeping my 3 topped off whenever I'm feeding the grid. Elon could make it so much better if he allowed API charge_current control. As it is now I leave it at 11 Amps (NEMA 14-50). Works fine with the reduced travel of SIP but really could be so much better with automated charge_current control.
You did not mention the hot-tub. When the excess is high bump up the tub temp past where you normally use it at night. Just don't forget to lower it!
...also, your last line “if the savings are minimal, it may not be worth the bother.”
As micro-grid operators it is our duty to optimize every little bit.
You get very little for feeding back into the grid so the idea is to use your solar before you "lose" it to the grid. Using solar on major appliances / loads during the day with the surplus being soaked up by the Powerwall seems to be the best strategy, lightening the load on the Powerwall (charge and discharge) as a side benefit.
The one thing I don't have is a large night time load as I only have a small ev which can charge during the day.
When eventually I get a larger ev which requires more electricity than my solar can produce, I will be interested to see if the Powerwall will "save" its charge when it sees a large load for hours during the off-peak period in the middle of the night (when you would set the ev to charge).
With the TOU settings this is how it works now if it has a relatively low SOC and there is an early morning peak period. In this case it will switch to grid during the off-peak period saving its SOC for the peak period when there will be insufficient solar power to support loads.
If we have days of low insolation, the Powerwall will actually take some charge from the grid during the off-peak period so that it is ready to discharge for any peak period.
I just got 1.46.0 for the Powerwalls. Now you can limit EV charging in a power outage. Sweet!
@adam.lippiatt - What country/state are you in? In California, you can't charge the PW from the grid, except for Storm watch.
Do you have a Wall Connector?
I'm on 1.46 and do not have that feature. My script automatically does that (except for charge_current of course) so I don't care. But, I'd like to know how charge_current is handled. I'd be interested if you run the test.
No WC, just a NEMA 6-50. I dialed down the charge to 16 amps in the car, as I'm not driving much these days with the lockdowns :( I don't think the feature matters how the car is charged as I think it communicates with the car directly.
It may be the 1.46 App charging EV limits in a power failure feature is only in select markets? There are so many strange laws about what you can and can't do in each area, it's amazing they can figure it all out. Just to be sure, it's in the app, under Customize, and you have to scroll down as it's below the Stormwatch feature.
FYI. I'm in So. CA, don't own a Tesla vehicle, am running 1.46.0 on the Powerwalls, and the "Vehicle Charging During Power Outage" option appears under "Storm Watch" option on my Android, which is running Tesla app version 3.10.5.
@teslatap.com - I am in Western Australia. We are allowed to charge from the network here. I can't work out why a power company wouldn't want you to (apart from the time you take it). The Powerwall is great - it will take from the network only during off-peak hours and rather than drawing electricity at full capacity will take what it wants over the extended period at a lower rate. The downside of our market is that we can only take electricity at the variable rates of the retailer, not at the wholesale price. Other States of Australia allow you to agree with a retailer exposure to the wholesale market which can potentially expose you to very low prices (at least at the energy level). That requires more management though - something not built into the Powerwall but could be with other control software.
I just got two PW installed so I’m still in the learning/investigative phase. I’m very cautious when it comes to batteries so I’m trying to see what routine would help me Avoid the wear n tear. I normally export to the grid so right now I’m on Self Powered at 95% but I’ve had a couple of rainy days so I’ve seen that 5% used and recharge multiple times on the same day. Not sure if switching to 100% for most of the day then changing to 95% once solar is gone would get me to only use that percentage once daily. Again, probably this question has been asked multiple times! So I’ll keep reading at the forums.
@Rubber Toe - The way Lithium batteries work is they have a lifetime that is defined by the number cycles of 100% SOC to 0% SOC and back to 100% SOC, where the battery has 30% degradation.
In practical terms the Powerwalls are rated for 5,000 cycles - meaning after 5,000 cycles it should have at least 70% capacity. So at end of life, they still have useful capacity, but not as much as new.
Ok, if you charge 100% SOC to 90% SOC and back to 100% SOC, that is only a tenth of a cycle, so you should be good for 50,000 cycles! These are all a rough guide, but in your example, you should be able to have 100,000 cycles with a setting of 95% and never using the backup feature. There could be other factors, but this is a good guideline to understanding battery longevity.
Tesla should implement an automatic mode here. Have the Energy Gateway talk to the car, and if it's plugged in AND you're generating excess energy that would otherwise go to the grid, tell the car to start charging and control the Amperage such that it will consume the extra energy, instead of sending it to the Utility Grid.
Given the ability of the newest software to slow the car's charge rate during an outage, this should be pretty simple for them to implement. Already demonstrated it's 100% possible to throttle the car automatically.
It should be pointed out that the PWs have an *unlimited cycle* ten-year warranty, if charged exclusively from the solar array.
I have a Zappi EV Charger that is designed to monitor excess solar and charge your EV from solar (you can adjust the solar/grid percentage to whatever you want) - https://myenergi.com/product/zappi/
But in addition to its standard features I wanted something that wasn't on offer, so I have 'hacked' my Zappi EV charger so it 'Boost Charges' when the variable tariff I am on drops below the rate I get paid for exporting my excess solar (the rates can change every 30 minutes) - https://youtu.be/vhnQqKtkb00
The only problem is that when the system activates it takes energy from my Powerwall (that I have filled with solar from my roof), rather than from the grid, where (at that time) it costs less to buy than the rate I get paid for exporting excess solar to the grid.
I can prevent this by manually switching my Powerwall to 'Back-Up Only' using the app, but I would really like to be able to do this automatically when the rate I am paying per kWh drops below my fixed export rate, as the lower prices often occur early in the morning, while I'm asleep.
If this could be done, there is a small added bonus in that if the Powerwall isn't fully charged when it switches over to 'Back-Up Only' it will charge to 100% at the cheaper rate.
Does anyone know how to automate switching over the 'Back-Up Only'? Can it be tied to a variable tariff threshold?
Being able to export from the Powerwall during peak demand periods would be nice, but in the summer I'm still creating excess solar through the peak periods and my house needs about half of my Powerwalls capacity to run till sun up the next day. In the winter I'm going to need everything that is in the Powerwall to run the house plus some from the grid, so no spare capacity then to sell then. Plus I'm currently on a fixed rate export tariff.
Maybe an electro-mechanical solution like my Zappi Charger 'hack' could be wired into the gateway to locally do the switching and bypass the app/web based control?
"Even if you use your EV daily to commute to work, it may be better to start charging as soon as you arrive home when you are still generating solar power." Oh no... thought it was common sense to take as much advantage of the sun as possible? Do many people seriously not charge when they get to their houses?
@60s_arthur - Well.. the pre-solar/Powerwall strategy is to charge at midnight when the rates are lowest. I was doing that for years. That assumes you have Time-of-use billing. If you don't have TOU, then it hasn't mattered when you charge.
Peak energy usage in So. CA is between 4PM and 9PM, which is when rates are the *highest*. People on that particular TOU will decidedly *not* charge their cars when they get home from work just after 5PM. Being retired, I typically charge my EV (BOLT) after my two PWs have fully charged, but before 4PM. This makes best use of the cleanest power produced by the grid from around noon to 4PM, when about half of the grid is being powered by renewables like solar, wind and hydro.