What is your Powerwall 2 charging rate?

[cwied]

I did my formatting slightly differently because I thought it might be a little more legible. The battery state axis is on the right, so it is peaking at 100%, not 10 kW. The key line is the blue "Battery Flow" line, which peaks (bottoms) out at -3.3 kW.

 

[Icepicknz]

Just got my tesla power walls installed today, 2 x power wall 2s.
I have just set it to backup mode and its charging at 3.3kw, so will take like 8 hours to charge both

 

[JeffreyY]

I get up to 20 on 4 PW2s aka 5 each

 

[Willy3]

I get up to 20 on 4 PW2s aka 5 each

Were you off grid when you took this screen shot? I’ve been trying to figure out what will happen if your solar system puts out more than your powerwalls can take if you have an outage or off grid. There is a debate about if a complete system would shut down if the solar array produces more than what the powerwalls can accept combined with what you are using. for example, what if your system had been producing 23kW in this instance? (23kW > 20kW + 2.7kW) Would it just shut down?

 

[JeffreyY]

Um. No, I was on grid but not exporting. I kind of doubt it would be so in-elegant to shut down, but I don't know the answer. It is quite easy for me to consume a lot during an outage though, just turn on the ACs.

 

[jboy210]

Were you off grid when you took this screen shot? I’ve been trying to figure out what will happen if your solar system puts out more than your powerwalls can take if you have an outage or off grid. There is a debate about if a complete system would shut down if the solar array produces more than what the powerwalls can accept combined with what you are using. for example, what if your system had been producing 23kW in this instance? (23kW > 20kW + 2.7kW) Would it just shut down?

The Powerwall gateway would shutdown the inverters if there was no place for the power to go. That is the Powerwalls are 100% and the grid was not available. It would do this by increasing the current frequency beyond the operational range of the inverter effectively taking it off line. When the Powerwalls had storage space from usage, or the grid comes back, the frequency would drop back into the operational range to bring the inverters back online.

This massive thread talks about this and the issue raising the frequency can have on devices like a UPS.

 

[Willy3]

Sorry, to be more specific, my uncertainty is what happens if when you are in an outage and the panels produce more than what the powerwall(s)are rated to charge at combined with what you are using.
If you are off grid and have 1 powerwall at 0%, what if your PV system is producing 9kW and the home is only using 1kW? Im trying to find out if anyone has experienced this scenario.
Better explained in this thread:
Just Ordered 16.32kW w/2 Powerwalls

 

[BrettS]

The Powerwall gateway would shutdown the inverters if there was no place for the power to go. That is the Powerwalls are 100% and the grid was not available. It would do this by increasing the current frequency beyond the operational range of the inverter effectively taking it off line. When the Powerwalls had storage space from usage, or the grid comes back, the frequency would drop back into the operational range to bring the inverters back online.

This massive thread talks about this and the issue raising the frequency can have on devices like a UPS.

Yes, it is well documented and many people have observed that the powerwalls will raise the line frequency to shut down the inverters when they are at 100%. However, the question that was asked here is a little different and we had another thread that was discussing this, but we never really came to a conclusion there.

The other concern is that each powerwall can charge at up to 5kW, so what happens when you are off grid and you have, say 2 powerwalls, but your solar system can produce 15kW. The house will use some of that and the powerwalls can absorb up to 10kW, but there may be extra power that can’t be used. Normally that would be sent back to the grid, but when you are off grid that can’t happen. One member said that in this case the entire system will shut down and your home will lose power.

@JeffreyY it looks like you might be able to test this. Would you be willing to go off grid on a bright sunny day while your powerwalls are not at full charge and lower the usage in your house such that there is more than 20kW that is not being used by your house. Since you have 4 powerwalls they should be able to absorb 20kW, but there should still be extra. Several others and myself would be very interested to see what happens. But do be aware that it has been predicted that your entire system will shut down, so at least be prepared for your house to lose power if you try this.

Thanks

 

[niveknow]

Would be very interested to see this testing as well. To properly document. My install is 5 weeks away otherwise I'd test myself.


Thanks,

 

[jboy210]

Yes, it is well documented and many people have observed that the powerwalls will raise the line frequency to shut down the inverters when they are at 100%. However, the question that was asked here is a little different and we had another thread that was discussing this, but we never really came to a conclusion there.

The other concern is that each powerwall can charge at up to 5kW, so what happens when you are off grid and you have, say 2 powerwalls, but your solar system can produce 15kW. The house will use some of that and the powerwalls can absorb up to 10kW, but there may be extra power that can’t be used. Normally that would be sent back to the grid, but when you are off grid that can’t happen. One member said that in this case the entire system will shut down and your home will lose power.

Interesting scenario. I would assume the gateway could continue by shutting down individual inverters. We have 2 inverters, on 8+ kw and one 4+ kW.

Alternatively, on my installation I have two breakers, one per inverter, in the generation panel plus off switches on each inverter. So if the gateway could not handle shutting a single inverter, I could manually cut off the output from an inverter at the generation panel breaker or by turning inverter's power switch to off.

So this scenario would only be a real issue if your max solar output from an inverter exceeds the capacity of the Powerwalls. Hopefully Tesla engineers the PW installations to avoid this case.

 

[MorrisonHiker]

On our system, when there is a real outage, the Powerwalls will continue to be charged. As they approach 100%, all three of our Delta Solivia inverters shut off but our SolarEdge inverter (with optimizers and a different shutoff frequency) can usually keep running. Eventually, the SolarEdge will shut off as well. As the Powerwalls drain, the SolarEdge inverter usually starts producing first. Eventually the Delta inverters start producing again but they will cycle off and on throughout an extended outage.

We did have a problem one day last year where we couldn't get our Powerwalls to charge even though we had a perfectly sunny day. It was cold out and the Powerwalls were down to 5% and they were raising the frequency to stay warm. This caused the solar to cycle on and off throughout the day. Since then, we haven't taken our Powerwalls that low. We've also added that SolarEdge inverter and a new array of 12 panels so I think we won't have that issue in the future. Hopefully the SolarEdge panels will be enough to trickle charge the Powerwalls back up slowly and then allow the Delta inverters to start producing again once the Powerwalls are sufficiently charged and warmed up.

 

[CrazyRabbit]

If your operating off grid and your solar output exceeds, say 16KW, your ability to charge your 5KW per powerwall charge rate, say you have two PW which would be 10KW. I’ve heard from users that your whole system will shutdown as you have exceeded the max allowed charge rate of 5KW per powerwall. It is best to purchase enough PWs so your charge rate can’t be exceeded.
Perhaps this has been fixed in the firmware now, and it will throttle the solar output by varying the frequency, like it does when the power walls are full Power curtailment by varying the frequency is by design and not limitation off the hardware as some has suggested. Inverters and current power supplies and don’t play well without some ware for the power to go. I believe some inverters can throttle the power based on frequency rather the on/off, or perhaps it is how you configure the gateway.

 

[BrettS]

Interesting scenario. I would assume the gateway could continue by shutting down individual inverters. We have 2 inverters, on 8+ kw and one 4+ kW.

This definitely can’t happen because the gateway has no way to control inverters individually. It can raise the frequency, but that will shut off all of the inverters. In the other thread someone had suggested that a potential workaround for this with two inverters would be that you connect one inverter to the critical loads panel and the other to the non backed up panel. Then if the power goes out only one of your inverters will operate and your solar capacity won’t be enough to overwhelm your powerwalls. However, this has the obvious downside of losing some of your solar capacity during an outage.

Alternatively, on my installation I have two breakers, one per inverter, in the generation panel plus off switches on each inverter. So if the gateway could not handle shutting a single inverter, I could manually cut off the output from an inverter at the generation panel breaker or by turning inverter's power switch to off.

That’s certainly a manual way to handle it, and IMO probably the better option. That way in the mornings and evenings and during cloudy weather you can have both inverters on and get the most our of your solar system, but if it’s sunny and you’re in danger of overwhelming the powerwalls then you could shut one off. Of, having to manually turn things on and off is still a pretty big downside.

So this scenario would only be a real issue if your max solar output from an inverter exceeds the capacity of the Powerwalls. Hopefully Tesla engineers the PW installations to avoid this case.

That’s true. It’s not a common problem and usually people with a larger solar system will also have a larger number of powerwalls, but it can and has come up before.

 

[Southpasfan]

Yep, no one has been able to test this yet, but in the end I solved it by ordering a third Powerwall. That had a couple of advantages, one, it eliminated, most likely, the issue of potentially having solar, a perfectly good powerwall, and ironically having the power go out, in an outage, despite having both panels and a charged powerwall. Second, the third Powerwall also, in my case, is a true whole house back up, which can likely also cover the issues when the A/C would start up. That means money should be saved because one does not need a backed up and non-backed-up subpanel. So, essentially the third powerwall has an additional discount built in.

 

[cwied]

Sorry, to be more specific, my uncertainty is what happens if when you are in an outage and the panels produce more than what the powerwall(s)are rated to charge at combined with what you are using.
If you are off grid and have 1 powerwall at 0%, what if your PV system is producing 9kW and the home is only using 1kW? Im trying to find out if anyone has experienced this scenario.
Better explained in this thread:
Just Ordered 16.32kW w/2 Powerwalls

It's been a while, but I'm pretty sure I remember somebody posting here that their system shut down in exactly this situation (power outage, solar producing more than the powerwalls could accept, powerwalls not full). Unfortunately this was a while ago, and I was unable to find the thread. I don't remember how they ended up with the configuration having more solar production than the Powerwalls could handle. It's possible that one of their Powerwalls was malfunctioning at the time. I'm pretty sure Tesla will not install such a configuration any more.