When you look at the OBD data verses the vehicle display, you need to remember that the OBD is showing the actual battery SOC whereas the display adjusts for the hidden battery buffer... which on an e-tron is at the top of the battery. Another issue is the chemistry. LFP (LiFePO4) vs NMC. A third is that degradation is non-linear. The battery degradation rate typically starts out steep at the beginning but slows down drastically after that. And a fourth is time, as I noticed another poster said. Calendar aging... but calendar aging is a bit of a beast to calculate because it is primarily a function of the battery voltage (of the cell voltage) x temperature. So this really depends on the temperatures the battery is exposed to and for how long... it will degrade more slowly in colder temperatures and at lower states of charge and more quickly at higher temperatures and higher states of charge. Extreme conditions cause greater problems. but nominal hot weather during the day might not necessarily cause faster aging because the battery is a huge mass so its ambient temperatures tends to be a combination of day + night temperatures. And chemistry as well... so for example, NMC will degrade faster when held at a high state of charge, which is why charging to 80% is recommended (some people even do 70%). But when a LFP battery is charged to 100% and charging stops, the cell voltage actually drops down significantly (while staying at 100% SOC), relieving some of the stress. When a LFP battery is drained even a little, even just down to 95%, the effects of calendar aging are greatly diminished and at 70% at 20-25C or so calendar aging pretty much stops. Lots of knobs.
If the intent is to use the Powerwall 2 solely for backup, with no time of use element to be concerned with, does it then make sense to set the charge level for the battery in as narrow a range as possible, say 75-80% to minimize charge/discharge, also avoiding harmful 100% level? This is consistent with the recommendation for daily driving of Tesla NMC battery vehicles. If the grid down you would get alerted by the app and you could lower the 75% to 20% or whatever minimum you are comfortable with.
Hey Dale! Great video as always. The Tesla rep told me directly that they would be able to replace the inverter from a PW3 for about $2500 cost out of warranty. Can you confirm on your end about the inverter not being able to be swapped? Thanks man!
You are missing one important parameter. Time influences the battery health. Not just the amount of MWh. Also need to take into account the battery size
Not to mention that in 15 yrs even if the Battery Cells themselves are still good and have 90+ capacity if one of the internal PCB control modules goes bad, a replacement part is most likely NOT going to be available. In CA the "right to repair" law will soon go into effect but it only covers a period of 7 years. It would be really nice if after the 7 year period and after a company discontinues spare parts they were required to post complete PCB schematics & firmware/software as open source so someone could reproduce the parts if desired. It just drives me crazy how all these lifetime cost benefit analysis or payback period calculations NEVER discuss the problem of repair parts becoming obsolete and then the consumer has to purchase a complete new item including installation costs before the projected lifetime is reached.
We would need to look at the cell level data to create a generalized rate time influences degradation. The size of the battery shouldn't be a variable as much as the voltage of the cells and packs.
Dale, I think part of me is seeing that all of the electric companies claim that they are charging the residential battery fully and then discharging it on a daily basis. This is very different from an auto. Whereby (most EV users) don’t fully discharge daily… in turn This degrades the battery as there is only a limited number of cycles that a battery can be charged and discharged. Hope this clarifies if not, please advise me!
The cycle behavior of a vehicle can create some variables but we do see this occur on sites that have less solar production in the winter and too much storage, the batteries don’t fully recharge. Also, most manufacturers on both sides, residential home batteries and electric vehicle batteries have two battery ratings true capacity and usable capacity. This improves the battery health over time
Plus, the powerwall just for backup should not degrade as much as the car because the car is up/down/ up down, which affects the longevity you would think. I have 2x powerwalls (#2) version, Max discharge is 10 kw continuous discharge. I’ve had them almost 3 years, lost power 94 times, longest one was 9 hours, but most were 10 minutes some a few hours. I installed mine in a workshop area so no rain, snow, extreme temperature fluctuations. Overall not heavy use as a backup. I’m sure if someone was using it to offset the grid charges by charging when cheaper and time of use works for your area. I just use mine as backup. Great information for a video. Is there any way I can see how my powerwalls have degraded? Do I just look at it when fully charged and if it’s 97% it means tgat is what I have lost = 3%?
This is something I'm very interested in. Just how long will my powerwall last? Anyway the powerwall (2 anyway) has an api you can monitor it directly and don't need to attempt the comparison and there should be enough out there for a reasonable guess to be made. I've been monitoring mine, which I've had since October 2023. First thing actual capacity of the powerwall is not 13.5KwH, it's 14, or at least that was what I thought, mine started out with 14507KwH according to the API. Why? I think Tesla has worked out it's in danger of having warranty claims and is seeking to mitigate. Today my powerwall is down to 14200KwH so it's lost 307 watts of capacity in less than 7 months, It is therefore on schedule to lose 526w a year, which is 5.2KwH over 10 years. 70% of 13.5KwH is 9.45KwH this is the promised capacity. Extrapolating my 10 years capacity I get 9.244KwH, which is slightly under. My battery is in a garage, but is being force discharged, so I will exceed the maximum rated out (more than likely) so my warranty will actually be less than 10 years 8-9 I think. Anyway there are lots of caveats my battery seems bigger than most, I've only had it 7 months, age related wear might cause an increased decline, etc. That said I don't think Tesla is kidding your battery will have just over 70% after 10 years ordinary use. 37 years seems unlikely.
Most batteries have a true capacity and a usable capacity. The last I heard the PW had a true capacity of 14kWh and the usable capacity is 13.5kWh. It’s possible that the batteries true capacity has increased over the years with units reaching 14.5kWh. Battery degradation isn’t as linear is you might think and a battery typically losses the most of its capacity in the first year before leveling off with a lower rate of degradation. Regardless there are a lot of variables, and not enough shared data to make a distinctive conclusion. Ideally these companies could publish their finds of real world battery SoC, and we can overlay them to seen if there is a pattern. Much like they have done with EV data sharing.
According to my Tesla STATS app my 2022 MYP with 20K miles (half are road trips using DCFC) the app reports I have lost 4.7% of its original rated range. And my Y is a Performance Y and I go WOT every chance I get especially if there is some kid in a Mustang around me. So my DISCHARGE data is probably on the HIGH side.
That sounds to be inline with most electric vehicles, the batteries need to settle in and the degradation slows down. Check out www.recurrentauto.com they will tell you how your vehicles doing compared to thousands of other ev owners.
I am coming to you via an iPad RUclips app, and I may be missing it, but I do not see the link to your odbc2 monitoring app that you said that you were going to provide in the description, please reply with it. Thank you.
When you look at the OBD data verses the vehicle display, you need to remember that the OBD is showing the actual battery SOC whereas the display adjusts for the hidden battery buffer... which on an e-tron is at the top of the battery.
Another issue is the chemistry. LFP (LiFePO4) vs NMC.
A third is that degradation is non-linear. The battery degradation rate typically starts out steep at the beginning but slows down drastically after that.
And a fourth is time, as I noticed another poster said. Calendar aging... but calendar aging is a bit of a beast to calculate because it is primarily a function of the battery voltage (of the cell voltage) x temperature. So this really depends on the temperatures the battery is exposed to and for how long... it will degrade more slowly in colder temperatures and at lower states of charge and more quickly at higher temperatures and higher states of charge.
Extreme conditions cause greater problems. but nominal hot weather during the day might not necessarily cause faster aging because the battery is a huge mass so its ambient temperatures tends to be a combination of day + night temperatures.
And chemistry as well... so for example, NMC will degrade faster when held at a high state of charge, which is why charging to 80% is recommended (some people even do 70%). But when a LFP battery is charged to 100% and charging stops, the cell voltage actually drops down significantly (while staying at 100% SOC), relieving some of the stress. When a LFP battery is drained even a little, even just down to 95%, the effects of calendar aging are greatly diminished and at 70% at 20-25C or so calendar aging pretty much stops.
Lots of knobs.
If the intent is to use the Powerwall 2 solely for backup, with no time of use element to be concerned with, does it then make sense to set the charge level for the battery in as narrow a range as possible, say 75-80% to minimize charge/discharge, also avoiding harmful 100% level? This is consistent with the recommendation for daily driving of Tesla NMC battery vehicles. If the grid down you would get alerted by the app and you could lower the 75% to 20% or whatever minimum you are comfortable with.
Hey Dale! Great video as always. The Tesla rep told me directly that they would be able to replace the inverter from a PW3 for about $2500 cost out of warranty. Can you confirm on your end about the inverter not being able to be swapped? Thanks man!
You are missing one important parameter. Time influences the battery health. Not just the amount of MWh. Also need to take into account the battery size
Not to mention that in 15 yrs even if the Battery Cells themselves are still good and have 90+ capacity if one of the internal PCB control modules goes bad, a replacement part is most likely NOT going to be available. In CA the "right to repair" law will soon go into effect but it only covers a period of 7 years. It would be really nice if after the 7 year period and after a company discontinues spare parts they were required to post complete PCB schematics & firmware/software as open source so someone could reproduce the parts if desired.
It just drives me crazy how all these lifetime cost benefit analysis or payback period calculations NEVER discuss the problem of repair parts becoming obsolete and then the consumer has to purchase a complete new item including installation costs before the projected lifetime is reached.
We would need to look at the cell level data to create a generalized rate time influences degradation. The size of the battery shouldn't be a variable as much as the voltage of the cells and packs.
We have a 2017 Ford Fusion Hybrid plug in. When new the battery provided 21 miles on a charge. Now 15 miles on a good day and the car has 70k miles.
Dale, I think part of me is seeing that all of the electric companies claim that they are charging the residential battery fully and then discharging it on a daily basis. This is very different from an auto. Whereby (most EV users) don’t fully discharge daily… in turn This degrades the battery as there is only a limited number of cycles that a battery can be charged and discharged. Hope this clarifies if not, please advise me!
The cycle behavior of a vehicle can create some variables but we do see this occur on sites that have less solar production in the winter and too much storage, the batteries don’t fully recharge. Also, most manufacturers on both sides, residential home batteries and electric vehicle batteries have two battery ratings true capacity and usable capacity. This improves the battery health over time
Plus, the powerwall just for backup should not degrade as much as the car because the car is up/down/ up down, which affects the longevity you would think. I have 2x powerwalls (#2) version, Max discharge is 10 kw continuous discharge. I’ve had them almost 3 years, lost power 94 times, longest one was 9 hours, but most were 10 minutes some a few hours. I installed mine in a workshop area so no rain, snow, extreme temperature fluctuations. Overall not heavy use as a backup. I’m sure if someone was using it to offset the grid charges by charging when cheaper and time of use works for your area. I just use mine as backup. Great information for a video. Is there any way I can see how my powerwalls have degraded? Do I just look at it when fully charged and if it’s 97% it means tgat is what I have lost = 3%?
Assuming the software reports the batteries true SoC.
This is something I'm very interested in. Just how long will my powerwall last? Anyway the powerwall (2 anyway) has an api you can monitor it directly and don't need to attempt the comparison and there should be enough out there for a reasonable guess to be made. I've been monitoring mine, which I've had since October 2023. First thing actual capacity of the powerwall is not 13.5KwH, it's 14, or at least that was what I thought, mine started out with 14507KwH according to the API. Why? I think Tesla has worked out it's in danger of having warranty claims and is seeking to mitigate. Today my powerwall is down to 14200KwH so it's lost 307 watts of capacity in less than 7 months, It is therefore on schedule to lose 526w a year, which is 5.2KwH over 10 years. 70% of 13.5KwH is 9.45KwH this is the promised capacity. Extrapolating my 10 years capacity I get 9.244KwH, which is slightly under. My battery is in a garage, but is being force discharged, so I will exceed the maximum rated out (more than likely) so my warranty will actually be less than 10 years 8-9 I think. Anyway there are lots of caveats my battery seems bigger than most, I've only had it 7 months, age related wear might cause an increased decline, etc. That said I don't think Tesla is kidding your battery will have just over 70% after 10 years ordinary use. 37 years seems unlikely.
Most batteries have a true capacity and a usable capacity. The last I heard the PW had a true capacity of 14kWh and the usable capacity is 13.5kWh. It’s possible that the batteries true capacity has increased over the years with units reaching 14.5kWh. Battery degradation isn’t as linear is you might think and a battery typically losses the most of its capacity in the first year before leveling off with a lower rate of degradation. Regardless there are a lot of variables, and not enough shared data to make a distinctive conclusion. Ideally these companies could publish their finds of real world battery SoC, and we can overlay them to seen if there is a pattern. Much like they have done with EV data sharing.
According to my Tesla STATS app my 2022 MYP with 20K miles (half are road trips using DCFC) the app reports I have lost 4.7% of its original rated range. And my Y is a Performance Y and I go WOT every chance I get especially if there is some kid in a Mustang around me. So my DISCHARGE data is probably on the HIGH side.
That sounds to be inline with most electric vehicles, the batteries need to settle in and the degradation slows down. Check out www.recurrentauto.com they will tell you how your vehicles doing compared to thousands of other ev owners.
I am coming to you via an iPad RUclips app, and I may be missing it, but I do not see the link to your odbc2 monitoring app that you said that you were going to provide in the description, please reply with it. Thank you.
www.amazon.com/Veepeak-Bluetooth-Diagnostic-Supports-Vehicles/dp/B076XVQMVS/ref=mp_s_a_1_5_sspa?crid=1X961ZZRBQ33M&dib=eyJ2IjoiMSJ9.8KjPNZSFTxwznA_LTJT4k9H26o96EUCp9dxkeP7GK0W7vQkgQJ2RHPxrWbQ-_hKXBJ7_NRfJdzkipwlbF-vXxkFG8x--gGQuW44mZPRLZcYTGujRIk0xQBXitzk26epSnBBpmdHjciJpHyMFt14q9RzUazpFE3yavFnU4p-FyzQ0jZ3LjpHde5UcwypURca0QEbSHdm2pc6iuLlvmd07Ig.3NGvRqIJGSYBsjwSjmWBEHwIE78uFFU32wC2GKwmhdw&dib_tag=se&keywords=elm327+obdii&qid=1715923439&sprefix=%2Caps%2C188&sr=8-5-spons&sp_csd=d2lkZ2V0TmFtZT1zcF9waG9uZV9zZWFyY2hfbXRm&psc=1
Forever...
Not likely, but it should last 15 to 25 years.