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

[sorka]

Currently, I have enough sun every day to charge up my powerwalls to 100% even in self consumption mode where I'm using power from solar first from the house with the left over going to the batteries. In advance mode, it would be even worse with 100% of solar going to batteries during off peak.

I'm throwing the breaker every day to turn off the batteries from the TEG at around 80 to 85% because I don't want them charging to 100% everyday. When peak time arrives, I switch from self consumption to advance so that 100% of solar goes to the grid at the highest price.

It's annoying to have to do this every day and even more so having to switch off the breakers to prevent the batteries from charging to 100% and then having to switch them back on right before peak time and switch the app back to advanced so that I can consume from the batteries during peak but not have them overcharge during off peak.

 

[h2ofun]

Currently, I have enough sun every day to charge up my powerwalls to 100% even in self consumption mode where I'm using power from solar first from the house with the left over going to the batteries. In advance mode, it would be even worse with 100% of solar going to batteries during off peak.

I'm throwing the breaker every day to turn off the batteries from the TEG at around 80 to 85% because I don't want them charging to 100% everyday. When peak time arrives, I switch from self consumption to advance so that 100% of solar goes to the grid at the highest price.

It's annoying to have to do this every day and even more so having to switch off the breakers to prevent the batteries from charging to 100% and then having to switch them back on right before peak time and switch the app back to advanced so that I can consume from the batteries during peak but not have them overcharge during off peak.

Why the need? I am letting my batteries recharge to 100% each day

 

[jjrandorin]

Currently, I have enough sun every day to charge up my powerwalls to 100% even in self consumption mode where I'm using power from solar first from the house with the left over going to the batteries. In advance mode, it would be even worse with 100% of solar going to batteries during off peak.

I'm throwing the breaker every day to turn off the batteries from the TEG at around 80 to 85% because I don't want them charging to 100% everyday. When peak time arrives, I switch from self consumption to advance so that 100% of solar goes to the grid at the highest price.

It's annoying to have to do this every day and even more so having to switch off the breakers to prevent the batteries from charging to 100% and then having to switch them back on right before peak time and switch the app back to advanced so that I can consume from the batteries during peak but not have them overcharge during off peak.

There isnt any guidance that says not to charge them to 100% (unlike the cars) and 100% isnt actually 100% (because they generally have a buffer above the 13.5 kW available).

Anyway, to answer your question, there isnt any way that I am aware of to stop charging the batteries to 100% (whats reported as 100% in the app).

I seem to remember someone here saying they did "something" custom to do that, but I dont remember what it was, and was not concerned about it because as I said there is no guidance not to charge to 100% and 100% isnt actually 100%.

 

[sorka]

There isnt any guidance that says not to charge them to 100% (unlike the cars) and 100% isnt actually 100% (because they generally have a buffer above the 13.5 kW available).

Anyway, to answer your question, there isnt any way that I am aware of to stop charging the batteries to 100% (whats reported as 100% in the app).

I seem to remember someone here saying they did "something" custom to do that, but I dont remember what it was, and was not concerned about it because as I said there is no guidance not to charge to 100% and 100% isnt actually 100%.

Yes, but it's well known that higher SOCs, even if not actually to 100% is still not as good as keeping it lower. What's 100% in reality? 90%? Does anyone know? Has there been a teardown to look at the cell size and count? Has anyone measured discharged capacity from a true 100% charge after filling up from storm watch?

At any rate, it's common knowledge (do your own googling for sources) that narrowing the SOC cycling range will net you a non linear increase in (k)wh lifespan for the equivalent number of charge/discharge cycles.

Combine heat with high SOCs and it's even worse. My powerwalls will be exposed to 100+ temps for 2 months out of the year, 105+ temps for 1 month, and 110+ temps for a few weeks every year.

 

[zanary]

Currently, I have enough sun every day to charge up my powerwalls to 100% even in self consumption mode where I'm using power from solar first from the house with the left over going to the batteries. In advance mode, it would be even worse with 100% of solar going to batteries during off peak.

I'm throwing the breaker every day to turn off the batteries from the TEG at around 80 to 85% because I don't want them charging to 100% everyday. When peak time arrives, I switch from self consumption to advance so that 100% of solar goes to the grid at the highest price.

It's annoying to have to do this every day and even more so having to switch off the breakers to prevent the batteries from charging to 100% and then having to switch them back on right before peak time and switch the app back to advanced so that I can consume from the batteries during peak but not have them overcharge during off peak.

100% is actually around 90%. No need to power down your Powerwalls.

When storm watch is activated, you'll see that when it shows 100%, it continues to charge, and the charging rate slowly gets down to 1 kw from the grid, so this is evidence that when it stops at 100% during normal operation, it is much lower (around 90%).

 

[cobra]

100% is actually around 90%. No need to power down your Powerwalls.

When storm watch is activated, you'll see that when it shows 100%, it continues to charge, and the charging rate slowly gets down to 1 kw from the grid, so this is evidence that when it stops at 100% during normal operation, it is much lower (around 90%).

So stormwatch allows charging above the reserve? (90-100% actual, rather than what the app shows? I think that's what you said...) To bad that is all hidden from users.

 

[eml2]

Just having SoC at higher level does not mean it is bad. Only when staying at high SoC for a long period of time is bad. Assuming you're not in backup mode, thus it will get discharged when the sun goes down. So, I won't worry too much about it.

Also, those circuit breakers are not designed to be switched on and off daily.

 

[skepticcyclist]

Just having SoC at higher level does not mean it is bad. Only when staying at high SoC for a long period of time is bad. Assuming you're not in backup mode, thus it will get discharged when the sun goes down. So, I won't worry too much about it.

Also, those circuit breakers are not designed to be switched on and off daily.

I was about to say that. The batteries only remained fully charged for just a few hours each day and he is probably doing more damage to the breakers than he is by allowing the batteries to remain fully charged for a few hours

 

[getakey]

in Stormwatch, my PWs will only charge to 99%. I assume that is a true 99% under that setting

 

[sorka]

I was about to say that. The batteries only remained fully charged for just a few hours each day and he is probably doing more damage to the breakers than he is by allowing the batteries to remain fully charged for a few hours

The breakers will last many uses being shut off every day and they're like $15 to replace.

Even if it's only 90%, it's still not great for lithium ion batteries, even SMC, to charge to 90% every single day.

 

[gpez]

Even if it's only 90%, it's still not great for lithium ion batteries, even SMC, to charge to 90% every single day.

Citation needed?

I understand general battery chemistry for things like Powerwalls implies that this is true but to believe these sorts statements I'd really like to see something from an authoritative source (Tesla?) that we should be using their product in a way they don't have native support for to extend the life of the batteries. I don't think such a thing exists and the best that we have, the warranty, seems to not care.

All of this breaker switching talk reminds me of my father (bless him) who still puts his cars in neutral at stop lights, despite them being modern automatic transmission cars, because he thinks it reduces wear and tear on the transmissions...

 

[sorka]

Citation needed?

There are literally thousands.

Proper Care Extends Li-Ion Battery Life

Li-ion battery lifetime depends on battery chemistry, depth of discharge, battery temperature and battery capacity termination level.

www.powerelectronics.com

https://www.mdpi.com/2076-3417/8/10/1825/pdf

 

[getakey]

There are literally thousands.

Proper Care Extends Li-Ion Battery Life

Li-ion battery lifetime depends on battery chemistry, depth of discharge, battery temperature and battery capacity termination level.

www.powerelectronics.com

https://www.mdpi.com/2076-3417/8/10/1825/pdf

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.

 

[getakey]

what would be more useful is to compare battery degradation for SOC 70%, 80%, 90%, 100%

Doesn't seem like Tesla is worried about it for PWs

 

[jjrandorin]

I have read umptymillion battery threads here, where people go back and forth just like this one is starting to do. I have seen studies, etc. I know that "whats best" would be keeping the battery at 50% state of charge, and never using it, per all the battery studies.

I also know that, my own model 3, has simply been plugged into my wall connector when at home with a set charge of 90% has much (much) less "battery degradation" than many other people who have a "charging procedure" of only plugging in every 3rd day or setting their battery charge level to 73.4565%.

I know that, unlike the model 3s at least, tesla warranties powerwalls for 10 years, unlimited cycles with 70% available capacity left. We could also expect that, if you kept the batteries at a state of charge of, say 70% they would likely have more capacity left than if you dont attempt to manage it. What we DONT know is, given two different sets of batteries, one micromanaged the way OP would like, and one cycled every day, how different would they be?

We all pay a lot of money for these things, so if it makes OP happy they can turn their powerwalls off every day, even though I dont believe they were made with that specific use in mind. I dont currently think there is a way to do what OP wants with the tesla software, but there may be some thing, somewhere.

To attempt to head off the "umptymillion and 1" battery discussion, the OP didnt ask what anyones opinion on what they were doing was, but asked if it was possible to set the state of charge lower than what tesla has designated. I dont believe it is, unless someone has a scripting type way. Lets not go down the rabbit hole of a debate on battery chemistry, since it wasnt asked " does anyone think this is a good idea".

 

[h2ofun]

what would be more useful is to compare battery degradation for SOC 70%, 80%, 90%, 100%

Doesn't seem like Tesla is worried about it for PWs

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

 

[getakey]

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

not suggesting you do, nor would I

 

[h2ofun]

not suggesting you do, nor would I

Comment was not directed at you. If ones want to adjust charge levels of their PW, for it. As I said, not on my radar for what these cost.

 

[skepticcyclist]

Wouldn’t it be easier to just flip the power switch off and on on the PW than to flip the breaker?

 

[jhn_]

The breakers will last many uses being shut off every day and they're like $15 to replace.

Even if it's only 90%, it's still not great for lithium ion batteries, even SMC, to charge to 90% every single day.

You paid thousands of dollars for some of the most advanced batteries and battery management software in the world. Use them as the manufacturer intend and covers in their warranty and stop beating yourself up trying to micromanage them. You don’t know better than the Tesla engineers.

If anything you might be doing harm to the batteries because their BMS might behave optimally when they are connected to a power source for all you know.