Any way to keep Powerwalls from charging without turning off their breakers?

[sorka]

I find that study a bit stupid unless I read it wrong. Admittedly I skimmed it. They are testing keeping it at 15% SOC versus 90% SOC. Who wants to keep their EV at 15%? For that matter who wants to keep their PW at 15%? They should have tested SOC at practical useful levels.

You're right you skimmed it.

 

[lucassaugen]

If you are worried about battery life then you shouldn't be discharging your battery everyday. If battery life is your biggest concern just run in advanced - cost saving mode. While you will get to 100% SoC everyday you won't drain your battery down as far each night which means fewer cycles.

Like others stated, while the app says 100% it isn't actually 100%. When you dig into the API and ask for the battery charge percentage it says something like 90% or 95%.

 

[sorka]

This is the last game I would play with the PW's. They have a 10 year warranty to 70%. Good enough for me

I have no doubt they'll have 70% after 10 years charging to 90% every day. I want them to last longer and SOC depth of charge is non linearly detrimental as max SOC increases.

 

[sorka]

If you are worried about battery life then you shouldn't be discharging your battery everyday. If battery life is your biggest concern just run in advanced - cost saving mode. While you will get to 100% SoC everyday you won't drain your battery down as far each night which means fewer cycles.

No. I want to use every kwh I can to offset partial and peak cost 100%. I just don't need to charge the battery to 100% to achieve that goal. I only need about 50% of the capacity to do that.

 

[skepticcyclist]

No. I want to use every kwh I can to offset partial and peak cost 100%. I just don't need to charge the battery to 100% to achieve that goal. I only need about 50% of the capacity to do that.

Cost savings will do exactly that.

 

[sorka]

Cost savings will do exactly that.

No only will it not, but under advanced cost savings, 100% of solar ends up going into the battery during off peak and all home usage comes off the grid resulting in the battery hitting 100% even faster, costing me 2.1 cents NBCs for each kwh I took off the grid that I could have consumed direct from solar, and 10% round trip costs into the battery for solar I could have consumed directly.

 

[skepticcyclist]

No only will it not, but under advanced cost savings, 100% of solar ends up going into the battery during off peak and all home usage comes off the grid resulting in the battery hitting 100% even faster, costing me 2.1 cents NBCs for each kwh I took off the grid that I could have consumed direct from solar, and 10% round trip costs into the battery for solar I could have consumed directly.

I was talking specially about offsetting every kWh. This is exactly what cost savings does.

 

[sorka]

I was talking specially about offsetting every kWh. This is exactly what cost savings does.

But its NOT the most cost effective way to do it. It results in higher than necessary kwh throughput on the batteries and unnecessary NBC from grid usage. i.e. higher grid costs and more wear on the battery. This is avoided by using self consumption mode during off peak and switching back to advanced costs savings for peak.

This has been beat to death a thousand times in this forum. I'm not discussing anything that hasn't already been picked apart many times.

 

[skepticcyclist]

But its NOT the most cost effective way to do it. It results in higher than necessary kwh throughput on the batteries and unnecessary NBC from grid usage. i.e. higher grid costs and more wear on the battery. This is avoided by using self consumption mode during off peak and switching back to advanced costs savings for peak.

This has been beat to death a thousand times in this forum. I'm not discussing anything that hasn't already been picked apart many times.

No it won’t. If you leave it in cost savings and use the battery only during peak time (and/or shoulder) you’ll use very little power from the PW and won’t need much to charge it the next day.

If you use 20% for example, it doesn’t matter if your battery goes between 60% and 80% full or 80% and 100% full. It’s still the same amount of wattage being used and charged each day for the battery. And difference on battery degradation won’t even be noticeable. It will save you the headache of turning the breakers off and on each day (BTW, why not just flip the switch on the battery instead?)

 

[sorka]

No it won’t. If you leave it in cost savings and use the battery only during peak time (and/or shoulder) you’ll use very little power from the PW and won’t need much to charge it the next day.

If you use 20% for example, it doesn’t matter if your battery goes between 60% and 80% full or 80% and 100% full. It’s still the same amount of wattage being used and charged each day for the battery. And difference on battery degradation won’t even be noticeable. It will save you the headache of turning the breakers off and on each day (BTW, why not just flip the switch on the battery instead?)

You didn't read my response. Everything I said is true about cost savings mode. Using cost saving during OFF PEAK while the sun is shining results in every kwh of solar going to the battery until it hits 100%. This is not as cost effective as consuming that power directly from solar rather than taking it off the grid and incurring the NBCs or losing it in round trip conversions when it wasn't necessary plus cycling the battery more because I used more power directly from the grid rather than directly from solar.

I have modeling dashboards that show every scenario under different settings PLUS the actual usage.

I added a new column in my dashboard for monthly and lifetime energy in and energy out on my powerwalls. The 3 PWs have taken in 2602 kwh and output 2229 kwh. This means they're roughly 86% efficient so I'm actually losing about 14% on the round trip.

 

[getakey]

I agree with skeptic. If you use 20%, doesn't matter if it is 60 to 80 or 80 to 100. You are going to take the same amount from the grid

 

[bemyax]

@sorka , My comment might sound facetious, but it's not. I kind of want to do what your original post was talking about. So. I have a very small solar array, I'm a low energy user, and I have one Powerwall. If I can corral a qualified installer to do it, I would like to stack a second PW in my system. Based on my average usage and production in the last month, if I set my reserve at 30%, I would not fill the two PWs past 70%. (using about the middle 40% every average day) I will have expired before the storage does. Then, it's someone else's problem.

So, my solution is to just keep piling on storage capacity until you would infrequently fill it all the way.

 

[sorka]

I agree with skeptic. If you use 20%, doesn't matter if it is 60 to 80 or 80 to 100. You are going to take the same amount from the grid

Still not true. Under advanced cost savings all solar goes straight to the battery and house consumption comes from the grid. By moving house consumption directly from solar (in self consumption mode) I offset that grid usage.

 

[getakey]

the point was if you manage the situation to always stop at 80%, then each day you will go from 60 to 80. If you left it alone PWs would go to 100% on Day1 and each subsequent day go from 80 to 100. You are using the same amount from the grid at the same times of the day

After PWs get to 80, solar goes to house. Same with when PWs get to 100 and it will be the same time of the day unless you manage the turn back on time as well

 

[sorka]

the point was if you manage the situation to always stop at 80%, then each day you will go from 60 to 80. If you left it alone PWs would go to 100% on Day1 and each subsequent day go from 80 to 100. You are using the same amount from the grid at the same times of the day

After PWs get to 80, solar goes to house. Same with when PWs get to 100 and it will be the same time of the day unless you manage the turn back on time as well

That's NOT the same thing as saying if I just leave it in advanced cost saving mode that it will "already do that". Regardless of which SOC range I'm keeping the battery at, advanced cost saving mode will result in either more usage from the grid (incurs NBCs) or more kwh in and out of the battery vs just consuming the power directly from the sun which is the least expensive option and doesn't suffer the penalty of NBC grid usage or conversion loss on the round trip to the battery.

The 60 - 80 vs 80 to 100 thing is an entirely different issue. And on that, I also think its way better for the battery to lower the average peak SOC so yea, 60 to 80 will result in less degradation for the same number of kwh pumped through in either range.

 

[skepticcyclist]

Use the balanced setting. All solar first goes to the house and only excess is used to charge the battery. Once the battery is full then excess goes to the grid. Your house will then use battery during peak. You can always adjust your peak to be longer so it uses the battery longer.

Or set shoulder longer. In balanced mode in shoulder when solar activity is low and not enough to run the house it will be supplemented by the battery and not the grid

 

[sorka]

Use the balanced setting. All solar first goes to the house and only excess is used to charge the battery. Once the battery is full then excess goes to the grid. Your house will then use battery during peak. You can always adjust your peak to be longer so it uses the battery longer.

Or set shoulder longer. In balanced mode in shoulder when solar activity is low and not enough to run the house it will be supplemented by the battery and not the grid

Balanced mode has never done that for me. I'll post a screen shot tomorrow. The only difference with balanced mode that I've seen is that instead of drawing power from the battery during peak, it draws it from the grid instead which is the worst time to do it.

 

[skepticcyclist]

Balanced mode has never done that for me. I'll post a screen shot tomorrow. The only difference with balanced mode that I've seen is that instead of drawing power from the battery during peak, it draws it from the grid instead which is the worst time to do it.

It will draw from the battery during mid peak/shoulder. The problem is you didn’t set a mid peak. Set peak to only be during the night. Set shoulder (the grey) to start at your usual peak time when the sun is still up. It will use both battery and solar during this time. The key is you have to have both peak and mid peak active.

Here’s I currently have mine set. My peak officially starts at 4:00 and goes to 9:00. But since the sun is out until 6:30 I have shoulder from 5:30 to 6:30. Then peak from 6:30 to 9:00. During the time from 5:30 to 6:30 solar is still producing but too low for my house. During this hour solar and battery will power the house. Then once the sun is gone or peak hits (whichever is first) the house will only use battery.

I also attached the current activity. Since I’m in peak right now my whole house is currently running on the battery.

You can alway make that grey section (mid peak/shoulder) longer so the house runs off the battery when you want it to. But you have to have a peak time too for it to work (even if it’s only for 30 minutes). If you don’t set a peak then it treats mid peak as peak.

 

[skepticcyclist]

Balanced mode has never done that for me. I'll post a screen shot tomorrow. The only difference with balanced mode that I've seen is that instead of drawing power from the battery during peak, it draws it from the grid instead which is the worst time to do it.

View attachment 648343View attachment 648344View attachment 648345

See if this works for you tomorrow. Set the grey mid peak to start at 3:00 and end at 7:00 (or whenever you sun sets). Then set the yellow peak to begin at 7:00 and go to midnight. I can assure you that from 3:00-7:00 you’ll still use solar and the battery will supplement when needed

Here’s a pic I posted on IG of my house using both battery and solar during mid peak/shoulder.

 

[getakey]

That's NOT the same thing as saying if I just leave it in advanced cost saving mode that it will "already do that". Regardless of which SOC range I'm keeping the battery at, advanced cost saving mode will result in either more usage from the grid (incurs NBCs) or more kwh in and out of the battery vs just consuming the power directly from the sun which is the least expensive option and doesn't suffer the penalty of NBC grid usage or conversion loss on the round trip to the battery.

The 60 - 80 vs 80 to 100 thing is an entirely different issue. And on that, I also think its way better for the battery to lower the average peak SOC so yea, 60 to 80 will result in less degradation for the same number of kwh pumped through in either range.

leaving it in Cost Saving will not result in more NBCs. You are dealing with pennies to maybe extend the live that you have no proof