Battery degradation on Model Y with LFP

[mathewparet@gm]

I've ordered a new Model Y which will come with LFP batteries. I do not have an option to charge at home. So I guess my only options to charge are:

1. Tesla Super charger
2. DC Fast charging by other providers (like NRMA in Sydney)
3. Destination charger (level 2)

Has anyone had experience using only superchargers or fast DC chargers with the new model Y with LFP batteries? How is the battery degradation?

 

[kelpcar]

In my case, it's actually cheaper to charger at Superchargers during off-peak hours than it is to charge at home. My Northern California PG&E rates are $0.32 for the first 1000 kWh, and then $0.39 for the next tier.

which PG&E plan is this? Even before the shift to TOU, the tiering (first 4 tiers, then 2) was tied to a mythical baseline average that no house with residents in could meet.

 

[TheLex]

which PG&E plan is this? Even before the shift to TOU, the tiering (first 4 tiers, then 2) was tied to a mythical baseline average that no house with residents in could meet.

I'm on E1 S. We have 4.2 kWh of solar. We get 480 kWh allowance on Tier 1. I also get an additional 526 kWh for medical baseline, giving us a total of 1006 kWh before we hit Tier 2. Tier 1 is @ $0.32 kWh. Tier 2 is at $0.39 kWh.

We live where it's well over 100° degree all summer long. It's going to be over 110° this weekend and next week. With 8 tons of air conditioning, if we switch to TOU, our AC bills between 3pm - 8pm when it's the hottest part of the day, will be VERY expensive.

So at least in the summers (which last from end of May to last week of Oct here), it's actually cheaper for me to charge off-peak at Superchargers.

 

[kelpcar]

I'm on E1 S. We have 4.2 kWh of solar. We get 480 kWh allowance on Tier 1. I also get an additional 526 kWh for medical baseline, giving us a total of 1006 kWh before we hit Tier 2. Tier 1 is @ $0.32 kWh. Tier 2 is at $0.39 kWh.

We live where it's well over 100° degree all summer long. It's going to be over 110° this weekend and next week. With 8 tons of air conditioning, if we switch to TOU, our AC bills between 3pm - 8pm when it's the hottest part of the day, will be VERY expensive.

So at least in the summers (which last from end of May to last week of Oct here), it's actually cheaper for me to charge off-peak at Superchargers.

got it. You're on NEM 1, I presume, as I believe all 2.0 customers had to take TOU-C or D. 1000 would cover me and the car, but no AC here.

Have you priced expanding your array, even if it forces you to 2.0 and a TOU plan? It would (should?) reset your 20 year contract before you'd be subjected to whatever PG&E terms they can force into 3.0, and power costs would be in the 8-11 cent range. I have seem some chatter that they will postpone it by 12 months, leaving plenty of time to figure it out, provided you have the open space.

My mileage is pretty low, so I'm charging 120-180 KWh/month to the car. 22-23 / day otherwise, so a 7.5KW system is slightly better than 100% of need.

 

[jrr6415sun]

Tesla manages the Supercharging session for optimal efficiency while protecting the battery. Tesla also tracks the lifetime charging history for each battery pack, i.e. keeps track of the number of times that a Supercharger has been used. Tesla has this covered, so don't worry too much about Supercharging.

Whenever charging (or discharging) a lithium battery for minimal stress and maintaining the storage capacity of the battery you want to limit the charging rate (also discharge rate) to 1 X C where C is the capacity of the battery in kWh.

The V3 Superchargers can reach 250kW peak charging rates but only for about 5 or 6 minutes before starting to taper down the charging rate. The V2 Superchargers can reach 150kW charging rates but they too taper down after 40% state of charge.

The Urban Superchargers are limited to 72kW, even lower than a V2 Supercharger after tapering off has started. Charging at an Urban Supercharger without first preconditioning the battery (very common if you live close by the Supercharger because you won't have enough drive time to enable fully preconditioning for Supercharging before reaching the Supercharger) means charging at 36kW which is going to stress the battery even less. Using an Urban Supercharger limits the charging rate close to or less than the ideal maximum of 1C. Charging using an Urban Supercharger will take a bit longer than using a V2 or V3 Supercharger but that gives you more time to shop or enjoy a meal before heading back to the Supercharger station to unplug to avoid idling charges while plugged in and not actively charging.

Most battery degradation takes place over the first few years, due to the natural aging of the battery independent of how the battery is charged or used.

I was at the tesla showroom yesterday and the employee was telling someone not to supercharge all the time because it ruins the battery. I would assume this is what they are telling their workers to say and she wasn't just saying bad things about the car on her own.

I had a 2020 model S. I don't know what the advertised range was at the time I bought it, maybe 400? but 2 years and 7 months of exclusive super charging (always kept the charge between 20-80%) and my range went down to 345. Maybe not what happens to every car but it's just a data point. I live in Florida so i'm sure the heat here does have some negative effect long term on the battery. Also not sure what the range would have been if I never used a supercharger.

 

[jrr6415sun]

How vital is it to precondition the battery before charging? Is it necessary before charging at a V2 or V3 Supercharger?

In my case, it's actually cheaper to charger at Superchargers during off-peak hours than it is to charge at home. My Northern California PG&E rates are $0.32 for the first 1000 kWh, and then $0.39 for the next tier.

I would look to see if PG&E offers off peak pricing. Duke energy just starting offering it and it's about $.05 cheaper to charge at night if you choose that option.

 

[TheLex]

I would look to see if PG&E offers off peak pricing. Duke energy just starting offering it and it's about $.05 cheaper to charge at night if you choose that option.

The problem with PG&E's off-peak pricing is it ends at 3 pm and doesn't start up again until after 9 pm. And 3-9 pm is when it's hot like the blazes here. Our AC bill during that time period would more than eat up any potential savings. I've run all the numbers multiple times, and our current rate plan is still cheaper based on how we live and use our HVAC.

 

[TheLex]

got it. You're on NEM 1, I presume, as I believe all 2.0 customers had to take TOU-C or D. 1000 would cover me and the car, but no AC here.

Have you priced expanding your array, even if it forces you to 2.0 and a TOU plan? It would (should?) reset your 20 year contract before you'd be subjected to whatever PG&E terms they can force into 3.0, and power costs would be in the 8-11 cent range. I have seem some chatter that they will postpone it by 12 months, leaving plenty of time to figure it out, provided you have the open space.

My mileage is pretty low, so I'm charging 120-180 KWh/month to the car. 22-23 / day otherwise, so a 7.5KW system is slightly better than 100% of need.

I'm thinking of adding another 4 kWh of solar to our system. We have the room on the roof. Or I could simply install it on the garage's roof.

I'm not sure what you're talking about regarding the "20 years contract"? Are you referring to the NEM 1 billing for solar that allows us to have tier 1,2,3? It looks like NEM2 forces the customer into TOU. That would get very expensive for us.

If I expanded my array, would that automatically force me into NEM 2? Or can I stay on NEM 1?

We just got the car. So far it seems we use about 60 kWh/week. We typically charge every 4-6 days depending on how many errands my wife has to run. Our mileage is 80% city driving, shuttling the kids back and forth, etc.

 

[TheLex]

I was at the tesla showroom yesterday and the employee was telling someone not to supercharge all the time because it ruins the battery. I would assume this is what they are telling their workers to say and she wasn't just saying bad things about the car on her own.

I had a 2020 model S. I don't know what the advertised range was at the time I bought it, maybe 400? but 2 years and 7 months of exclusive super charging (always kept the charge between 20-80%) and my range went down to 345. Maybe not what happens to every car but it's just a data point. I live in Florida so i'm sure the heat here does have some negative effect long term on the battery. Also not sure what the range would have been if I never used a supercharger.

So in 2.5 years of use, your battery range has declined about 16%. I wonder if that's about average? I do read posts from folks who've experienced 10% range loss within the first year.

 

[jcanoe]

So far it seems we use about 60 kWh/week. We typically charge every 4-6 days depending

Tesla recommends leaving the Tesla Model Y plugged in when not in use. You don't necessarily have to charge every single day but you may want to charge your Model Y every day or every other day. This can help you to keep the battery state of charge (SOC) around the optimum charge level, i.e. ~60% SOC.

 

[Mrbrock]

Thanks for the data. However doesn't the battery lose capacity over time (especially the first year) anyway? I've seen multiple posts from folks saying they were charging at home and still suffered up to a 10% loss of range after the first few months to 1 year.

Yes, but it is usually linear. My data is not linear and shows direct correlation with supercharging.

 

[yesimon]

I thought supercharging is bad for the battery!

Yes, but it is usually linear. My data is not linear and shows direct correlation with supercharging.

To be clear to original subject and poster, LFP is resistant to all forms of cycling degradation including supercharging. Research indicates that LFP needs to be charged at 4C (15 minute full charge) to see significant charging-related degradation.

 

[kelpcar]

Tesla recommends leaving the Tesla Model Y plugged in when not in use. You don't necessarily have to charge every single day but you may want to charge your Model Y every day or every other day. This can help you to keep the battery state of charge (SOC) around the optimum charge level, i.e. ~60% SOC.

but why? The rationalization here isn't well founded. I leave it in the 40-60 range, bump up if its under or if I anticipate a longer drive tomorrow.

 

[norazi]

LFP batteries are extremely durable... Like in the range of 2-5x more cycles than NCA li-ion. It would take 10+ years to see noticeable degradation. You can also charge LFP to 100% with little negative effects. I honestly wouldn't worry about it

 

[kelpcar]

I'm thinking of adding another 4 kWh of solar to our system. We have the room on the roof. Or I could simply install it on the garage's roof.

I'm not sure what you're talking about regarding the "20 years contract"? Are you referring to the NEM 1 billing for solar that allows us to have tier 1,2,3? It looks like NEM2 forces the customer into TOU. That would get very expensive for us.

If I expanded my array, would that automatically force me into NEM 2? Or can I stay on NEM 1?

We just got the car. So far it seems we use about 60 kWh/week. We typically charge every 4-6 days depending on how many errands my wife has to run. Our mileage is 80% city driving, shuttling the kids back and forth, etc.

I believe that NEM 1 customers could add 10% or 1 KW and not need to go to 2.0.

You've shown why TOU would not be ideal for you, but how many years have you been on nem1? The Nem agreements are 20 year contracts - at the end of it, you would shift to whatever is the current policy. And if you're past the half way mark, even the less idea TOU options may be preferable to what's being proposed in 3. I believe (but the installer would have to qualify) that you could start a new 20 year arrangement. (The 3.0 proposal last December sought to reduce that to 15, but I think would have lead to litigation)

3 would reduce the benefit of overproduction in summer, and even between day and night. It was a stick rather than a carrot to encourage people to install home batteries. It's unclear how the next proposal will go, but at least some of that will remain.

I also spent a little time looking into any practical applications for an additional array of panels that is not grid tied - that fed into batteries/evs that might be grid attached, but no generation would cross over. A lot of hypotheticals due to the possibility of having to pay PG&E $8/month/installed KW for grid tie.

 

[jcanoe]

but why? The rationalization here isn't well founded. I leave it in the 40-60 range, bump up if its under or if I anticipate a longer drive tomorrow.

Are you asking why Tesla recommends leaving the Tesla vehicle plugged in when not in use? I've given up trying to understand such things, do what makes sense to me.

 

[Art84]

Standard procedure for me: came home - plugged in. Tesla recommends doing it, it's also convenient to me. I always know, that if I need to drive somewhere, my car is always charged.

This is what I always did with my phones by the way.. always plug in for overnight charging, regardless of the charge level for the battery. This helps to avoid the situations when I need to search charging during the day

 

[TheLex]

I believe that NEM 1 customers could add 10% or 1 KW and not need to go to 2.0.

You've shown why TOU would not be ideal for you, but how many years have you been on nem1? The Nem agreements are 20 year contracts - at the end of it, you would shift to whatever is the current policy. And if you're past the half way mark, even the less idea TOU options may be preferable to what's being proposed in 3. I believe (but the installer would have to qualify) that you could start a new 20 year arrangement. (The 3.0 proposal last December sought to reduce that to 15, but I think would have lead to litigation)

3 would reduce the benefit of overproduction in summer, and even between day and night. It was a stick rather than a carrot to encourage people to install home batteries. It's unclear how the next proposal will go, but at least some of that will remain.

I also spent a little time looking into any practical applications for an additional array of panels that is not grid tied - that fed into batteries/evs that might be grid attached, but no generation would cross over. A lot of hypotheticals due to the possibility of having to pay PG&E $8/month/installed KW for grid tie.

We've been on NEM1 since 2014. So we have 12 years left on that rate plan. And you're right. NEM3 looks much worse. The California PUC has not finalized NEM3, so I guess I need to make a decision soon. Batteries are a nice solution, but a very expensive one. Unless one is very well versed in solar systems and electrical design, it's not practical to buy the Chinese made individual cells to make up a big lithium battery bank. The simpler solution would be a Tesla Powerwall but it's $14k for each one the last time I inquired. Capacity of the PW2 is 13.5 kWh. During yesterday's 113° temps, we used 33 kWh from 3-9 pm. So this is a solution that can get very expensive very quickly.

It sounds like the best solution for us would to remain grid-tied, but double the size of our 4.2 kWh solar system. That would force us into NEM2, but the increased solar output should make up for the higher rate ($0.39 increased to $0.47). We're having a $150-200/mo true each month during the summers, so the extra solar capacity would zero that out.

 

[Physicslawyer]

I Supercharged 15.5k miles in five months on a MYP exclusively and there was a 6.6% to 7.9% degradation of the battery (it fluctuated between 279 and 283 miles). That seems consistent with that mileage with people who have never Supercharged. This doesn't take time into account though, so I'm wondering if the loss would be greater if this had been done over a year.

You are lucky to have a LFP MY. I would absolutely love to have one of those based on our crazy high 50k/mile per year useage (my commute is 120 miles per day and we travel between homes weekly). We are signed up for a M3 with the LFP for the battery, but the MY has so many advantages. It's not an option in the US.