Discussion: Powerwall 3 [Speculation / Discussion etc]

[Iain]

I received an email from level 2 support. They have looked at my powerwalls and seen they drop to 79% quickly because of high loads. So as I sit here on hold ( they gave me a number if I have questions) my first question is what incredible charge rate was I getting to jump from 79% to 89% within a minute especially since I’m not even connected to the grid ( still waiting for PTO)

 

[offandonagain]

Related to the PW3 SoC issues, I noticed this on the Enphase forums:

https://support.enphase.com/s/question/0D53m00007nsx2eCAA

This jump in the state of charge (SoC) happens when the Enphase system calibrates the battery. This kind of jump in SoC usually occurs at the extreme ends, i.e., towards 5% or 100%, but sometimes when the difference between SoC displayed and calculated based on cell voltage crosses the threshold point, the system corrects that immediately.

Enphase batteries use LFP chemistry. I'm not sure if it was ever confirmed that PW3 uses LFP, but this makes me wonder if it's a related issue.

 

[ACarneiro]

Related to the PW3 SoC issues, I noticed this on the Enphase forums:

https://support.enphase.com/s/question/0D53m00007nsx2eCAA

Enphase batteries use LFP chemistry. I'm not sure if it was ever confirmed that PW3 uses LFP, but this makes me wonder if it's a related issue.

It would make a lot of sense, bearing in mind how much flatter the voltage curve is for States of Charge on LFP chemistry…

 

[Grayson73]

I received an email from level 2 support. They have looked at my powerwalls and seen they drop to 79% quickly because of high loads. So as I sit here on hold ( they gave me a number if I have questions) my first question is what incredible charge rate was I getting to jump from 79% to 89% within a minute especially since I’m not even connected to the grid ( still waiting for PTO)

Exactly. I also asked them why it jumped UP 17% in 15 minutes time. The Powerwalls can't even charge that quickly on grid.

 

[Grayson73]

Related to the PW3 SoC issues, I noticed this on the Enphase forums:

https://support.enphase.com/s/question/0D53m00007nsx2eCAA

Enphase batteries use LFP chemistry. I'm not sure if it was ever confirmed that PW3 uses LFP, but this makes me wonder if it's a related issue.

Thanks for that, but that would mean mine is correcting itself multiple times a day over many days with no permanent correction haha. I guess they need to update their software for LFP chemistry. I wonder if this means that we're not able to use or charge parts of the battery since it thinks it's full or empty when it actually is not.

 

[miimura]

The LFP mis-calibration only makes sense if you are going toward the ends of the SOC range. For example, as you are charging, it makes sense that it would suddenly jump higher from 88% to 100% as it reaches the high shutoff voltage. As it's dropping away from 100% it should rely on coulomb counting to estimate the SOC and not have any discontinuity in SOC estimation until it reaches low SOC.

 

[Iain]

A quick update regarding my PW3’s.

I received PTO a couple of days ago and since SDGE has allowed my system to export to the grid my PW’s are performing perfectly. I had a open issue with Tesla and I have no idea if they pushed a software update or it’s all coincidental but all is good and I have canceled my Tesla support request

 

[Grayson73]

More info:

Saturday it went down from 100% to 83% from 9:15am-9:30am with only 0.8 kWh discharged. That should only be 3% of 27 kWh, not 17%

Yesterday 2/20/24 it went up from 68% to 85% from 2:30pm-2:45pm

Today 2/21/24 it went up from 71% to 88% from 2:15pm-2:30pm

For some reason, all the jumps are 17%.

Chatted with Tesla online and they said "I have escalated the concern to our Tier 2 to double check the system. Please allow up to 5 business days for their review. "

Tesla got back to me and said this:

"Here are the findings from our Tier 2 team. The battery thinks it's at a different percent of charge than it actually is. By default the firmware is supposed to correct this at either end of charge or end of discharge however it can jump in the middle of charge like that. This may be further optimized in the future but there is nothing wrong with the battery. If you have any questions or concerns, we can be reached at 877-961-7652."

I did charge to 100% and discharge to 0%, but it didn't fix the issue. I hope that, similar to lain, that when I get PTO, the issue will be resolved.

 

[xrg458]

5kW Battery Charging Limit

With regards to 5kW battery charging limit on PW3, if one adds a second PW3 battery expansion module (no inverter) when they get released later in the year, is the expectation/understanding that it will be 5kW *per* battery so 10kW battery charging in this case despite a single inverter?

Supporting up to 20kW of panels on the roof is great, but if you can't do more than "trickle" charge a multi-battery stack within limited sunlight production hours got to think this is a bit backward and indeed is behind other manufacturer's hybrid inverter max battery charging limits.

 

[mongo]

5kW Battery Charging Limit

With regards to 5kW battery charging limit on PW3, if one adds a second PW3 battery expansion module (no inverter) when they get released later in the year, is the expectation/understanding that it will be 5kW *per* battery so 10kW battery charging in this case despite a single inverter?

Supporting up to 20kW of panels on the roof is great, but if you can't do more than "trickle" charge a multi-battery stack within limited sunlight production hours got to think this is a bit backward and indeed is behind other manufacturer's hybrid inverter max battery charging limits.

Per battery and Gateway limits their collective grid draw.

 

[Vines]

5kW Battery Charging Limit

With regards to 5kW battery charging limit on PW3, if one adds a second PW3 battery expansion module (no inverter) when they get released later in the year, is the expectation/understanding that it will be 5kW *per* battery so 10kW battery charging in this case despite a single inverter?

Supporting up to 20kW of panels on the roof is great, but if you can't do more than "trickle" charge a multi-battery stack within limited sunlight production hours got to think this is a bit backward and indeed is behind other manufacturer's hybrid inverter max battery charging limits.

I would expect that if you bought a second battery without a second inverter it would be limited somehow. Since this feature isnt really released, nobody really knows the answer to your question. I would expect 5 kW to be a reasonable charge rate for a 28 kWh battery stack. That means that you could totally recharge in less than 6 hours at a rate of approximately 0.2 C. By no means a trickle charge but some users might want even faster.

Theoretically, it has an 11.5 kW inverter and a 60A breaker connection so it could be the actual charge limit is higher.

 

[ACarneiro]

I would expect that if you bought a second battery without a second inverter it would be limited somehow. Since this feature isnt rel; released, nobody really knows the answer to your question. I would expect 5 kW to be a reasonable charge rate for a 28 kWh battery stack. That means that you could totally recharge in less than 6 hours at a rate of approximately 0.2 C. By no means a trickle charge but some users might want even faster.

Theoretically, it has an 11.5 kW inverter and a 60A breaker connection so it could be the actual charge limit is higher.

What you say makes sense but it would seem to be a very significant drop in an I important metric for the system as compared to the PW2 and 2+.
You can get 5kWp from a not-very-large solar array. From what I have seen in the US your systems seem to be bigger than here in Europe (I suspect your roofs are larger on average so you have more space for more panels).
A system limited to a 5kW charge rate would be "wasting" a lot of solar during the day which sort of negates the whole concept of self-consumption.

You're right that it's too early to tell but I will be very surprised if the 5kW limit remains fixed when you add subsequent battery packs.

 

[mongo]

What you say makes sense but it would seem to be a very significant drop in an I important metric for the system as compared to the PW2 and 2+.
You can get 5kWp from a not-very-large. From what I have seen in the US your systems seem to be bigger than here in Europe (I suspect your roofs are larger on average so you have more space for more panels).
A system limited to a 5kW charge rate would be "wasting" a lot of solar during the day which sort of negates the whole concept of self-consumption.

You're right that it's too early to tell but I will be very surprised if the 5kW limit remains fixed when you add subsequent battery packs.

Given the PW3's DC-DC-AC architecture, I expect the battery expansions allow an additional 5kW draw each from solar (up to solar limit, 20kW = 4*5kW). It possibly can increase draw from the grid as well since the inverter is good for 11.5 kW output, but the spec sheet only calls out the 5kW limit.

Also, ignore my previous post, I missed the part about a battery expansion, not a full additional unit.
https://digitalassets.tesla.com/tesla-contents/image/upload/Powerwall_3_Datasheet_NA-EN.pdf

 

[Grayson73]

I have 2 PW3s and my max charge rate so far today is 6.15 kW (I generated 6.7 kW at the time). Charging from the grid has been slow for some reason.

 

[mongo]

I have 2 PW3s and my max charge rate so far today is 6.15 kW (I generated 6.7 kW at the time).

Is that two full PW3 each with their own solar?

 

[Grayson73]

Is that two full PW3 each with their own solar?

No. Both are connected to the same 14.175 kW array.

 

[mongo]

No. Both are connected to the same 14.175 kW array.

So solar->PW3<->PW3_battery_only ?

 

[Vines]

So solar->PW3<->PW3_battery_only ?

For now, I heard PW3 designs recommend splitting PV production across multiple PW3 in one system. I would be surprised that this is a DC expansion as I haven't heard of this being available yet.

 

[mongo]

For now, I heard PW3 designs recommend splitting PV production across multiple PW3 in one system. I would be surprised that this is a DC expansion as I haven't heard of this being available yet.

Right, so two full PW3 each with solar connections to the array, but not sharing individual strings.

 

[Grayson73]

So solar->PW3<->PW3_battery_only ?

You are right, it doesn't look like they share strings.