Powerwall 2 Available Energy After 2 Years

[tom_kauf]

Same PW2 SW version. I’m logging on using a web browser on a desktop computer, not a phone. The User Agent that is passed by the browser might make a difference.

Was a good idea, but no difference unfortunately (Laptop on Windows 10, MS Edge).

 

[offandonagain]

Folks on this forum found this gem: if you click Continue on that page, then scroll all the way to the bottom and click Upgrade Later, you should be able to get to the old login page.

 

[Vines]

I went to the Installer view for my 5 units and found the total pack energy to be just over 72 kWh. Hope that is accurate, as its higher than I expected after almost 2 year.

 

[tom_kauf]

Folks on this forum found this gem: if you click Continue on that page, then scroll all the way to the bottom and click Upgrade Later, you should be able to get to the old login page.

That works, thanks.

 

[Steerpike]

I haven't recorded full pack energy regularly but from 2 readings and assuming original capacity of 14,000 in October 2020 I see about 4% degradation in 40 months down to 13,424 now. Annual degradation in the first two years 1.19% and 1.35% in the last year. Assuming the annual increase in the rate of degradation does not increase too much, should be well over 70% after 10 years of use.

 

[Vostok]

I haven't recorded full pack energy regularly but from 2 readings and assuming original capacity of 14,000 in October 2020 I see about 4% degradation in 40 months down to 13,424 now. Annual degradation in the first two years 1.19% and 1.35% in the last year. Assuming the annual increase in the rate of degradation does not increase too much, should be well over 70% after 10 years of use.

I've been recording the available pack capacity weekly from 30 months post-installation (with a 6 month gap in data collection). This is what my degradation looks like:

Something happened recently to cause it to lose 1.2% over 4 weeks... but I don't know what that is. It will be interesting to see if it is a "blip" or something more serious.

The linear trend suggests I'll be eligible for a warranty replacement after 7 years 4 months.

 

[jgleigh]

The warranty isn't 70% of initial capacity, it's 70% of 13.5 kWh.

 

[Steerpike]

@Vostok

What is really surprising about your graph is the bit that is missing!

If I am reading it correctly, your PW lost about 20% capacity in the first 30 months and about 6% in the second 30 months?

 

[sorka]

Mine are down about 2% in the first 40 months.

 

[Vostok]

The warranty isn't 70% of initial capacity, it's 70% of 13.5 kWh.

The warranty document says its 70% of 13.2 kWh, which is what I’ve used in my chart.

 

[Vostok]

What is really surprising about your graph is the bit that is missing! If I am reading it correctly, your PW lost about 20% capacity in the first 30 months and about 6% in the second 30 months?

Indeed that is the odd thing. If I linear trend the data backwards to installation, I started with only 83% of the warranted initial “usable capacity” of 13.2 kWh. So either my battery for some reason was massively under-spec on usable capacity from the start, or it suffered extremely rapid and unusual degradation in the first 2 years for who knows what reason.

Either way, it looks like a warranty replacement will eventually come my way.

 

[aesculus]

Indeed that is the odd thing. If I linear trend the data backwards to installation, I started with only 83% of the warranted initial “usable capacity” of 13.2 kWh. So either my battery for some reason was massively under-spec on usable capacity from the start, or it suffered extremely rapid and unusual degradation in the first 2 years for who knows what reason.

Not that it is a huge difference but UK PWs say they have 13.5 kWh usable. I wonder if yours are the same, since you are 2 phase?

 

[Vostok]

Not that it is a huge difference but UK PWs say they have 13.5 kWh usable. I wonder if yours are the same, since you are 2 phase?

Well I have 3-phase power to my house but the PW2 is a single-phase installation. The warranty document here says 13.2 kWh usable. It is not dependent on how many grid phases you have.

 

[jgleigh]

The USA warranty says 13.5 kWh. Interesting that it's slightly different between countries.

 

[Jeremy3292]

TBH I have a somewhat similar situation myself, which is why I mentioned to you to call via phone. I have about 25% degradation, according to Tesla Energy Tier 1 support, and my powerwalls are about 1.5 years old. For about 24 hours it made me frustrated, then I thought to myself: There is no way that these things wont degrade another 5% in the next 8.5 years. So, I am not sure how you feel about it, OP, but what this means to me is that at some point they will drop below the value for warranty replacement, and they will have to be replaced.

OP, I use self powered mode, no idea what mode you use. I have not changed anything about my usage pattern at all. My reserve is set to 20% right now, and I go from 100% to about 25% daily, and am using virtually no energy from the electrical grid, same as I did last year.

Said another way, I am continuing to "use my powerwalls" with the expectation that, at some point in the next couple of years, they will lose another few percentage points of capacity, and will need to be warranty replaced. I have no qualms at all about "using the battery" because I am simply using it in the manner it was designed.

I came to the realization that I would much rather have this much degradation in the powerwalls now, than have them be at 26% in year 9 or something, where they would likely (with my luck) drop below the warranty value right after the 10 year installation anniversary.

How are they looking now almost 3 years later? Did you get a replacement?

 

[bmah]

I finally decided to read through this whole thread and figure out how my system is faring. 3 PW2 units installed in March 2019.

dock2:~% cat sys.json | jq . | grep nominal_full_pack_energy
"nominal_full_pack_energy": 31922,
"nominal_full_pack_energy": 10746,
"nominal_full_pack_energy": 10612,
"nominal_full_pack_energy": 10564,

(In case it's not clear, the first number is the entire system, the remaining three are for each battery individually.)

If I did the math right, it's about about 22% loss over ~2.5 years, compared the figures posted by @kairojya a few posts above. Calculations based on some measurements over the last 12 hours give a slightly better picture...33.3 kWh system capacity for a loss of about 18% (assuming a baseline of 13.5 kWh x 3 = 40.5 kWh).

I should probably add some fields from the system_status output to my logging.

Bruce.

...a couple years later...

Same 3 x PW2s, now 5 years old...charged from the same 5.8kW solar system (now 14-ish years old). Time-Based-Control (formerly "Cost Saving Mode"), seasonally adjusted reserve between 20% and 50%.

kaga:~/Downloads% cat system_status.json | jq . | grep nominal_full_pack_energy
"nominal_full_pack_energy": 30428,
"nominal_full_pack_energy": 10216,
"nominal_full_pack_energy": 10134,
"nominal_full_pack_energy": 10078,

This looks like about 25% loss now. Assuming I started with 13.5kW capacity in each battery, this degradation is definitely not linear (which is good).

Bruce.

PS. I wish I could remember what I did to get the "measurements over the last 12 hours" in my last post. Maybe rebooted the gateway? Not going to mess with it now.

 

[miimura]

Now 6 years after installation.

"PackagePartNumber":"1092170-03-G"
"nominal_full_pack_energy":13084, "energy_charged":9780472,"energy_discharged":8363169

"PackagePartNumber":"1092170-03-G"
"nominal_full_pack_energy":13150, "energy_charged":9950616,"energy_discharged":8433076

 

[bmah]

Now 6 years after installation.

"PackagePartNumber":"1092170-03-G"
"nominal_full_pack_energy":13084, "energy_charged":9780472,"energy_discharged":8363169

"PackagePartNumber":"1092170-03-G"
"nominal_full_pack_energy":13150, "energy_charged":9950616,"energy_discharged":8433076

Nice. So jelly!

Bruce.

 

[jjrandorin]

How are they looking now almost 3 years later? Did you get a replacement?

Sorry for the late response. As some may have noticed (or not /shrug) I havent been here for a couple of months. In any case, to answer your question, Tesla did eventually replace them, after quite a bit of back and forth and patience on my part (months worth, always polite on my end, and patient).

My replacement powerwalls have a total pack energy around 14.6kWh each and have been installed for a little over a year now.

 

[jhn_]

Now 6 years after installation.

"PackagePartNumber":"1092170-03-G"
"nominal_full_pack_energy":13084, "energy_charged":9780472,"energy_discharged":8363169

"PackagePartNumber":"1092170-03-G"
"nominal_full_pack_energy":13150, "energy_charged":9950616,"energy_discharged":8433076

Yeah I’m at around 13380 each on my three PW2s just over three and a quarter years post install. My PWs are cycled daily from 100-33%. I don’t have a data point from install but I’m going to guess that my total pack energy might have been closer to 15000 on install like @jjrandorin’s replacements.

And that is about in line with the nominal 2170 cell degradation of 10-15% over the first 3-5 years posted online in numerous places, usually referring to their use in Tesla cars though.