Daily Home Charging Best Practice

[Daniel2022AT]

I finally have my Lucid Air Touring (for one week) after waiting 9 months so I am now focused on topics I never paid attention to before. Today, I am obsessing about the optimal home charging regime with battery life in mind. I know there are multiple posting on this topic, so I apologize for the repetition, but the postings and debate still seem inconclusive to me.

Lucid says to plug in whenever not driving having something to do withy battery conditioning which I think matters in an environment of either hot (>80F) or cold (<40F) ambient temperatures. Obviously the 80-20 SoC rule holds, but the are multiple factors to consider and many different opinions abound. The opposing best practices I have heard are distilled to:

A.) Plug in and top off every night, however, max charge should be ideally 60% or 70% for optimal battery health, unless you need the range the next day then 80% is OK. Maintaining optimal battery temp is important for range and battery health so plug in which conditions the battery.

B.) Do not top off every night, battery life is driven by minimizing number of charging cycles even in the middle of the SoC range. Just plug in when in the 20-30% range.

Only one of these is directionally correct, subject to specifics.

Related question: Is there any battery conditioning happening after the charging cycle has ended and the charge limit has been reached, i.e., trickle charging?

As a sidebar, I have a time-of-use (TOU) rate plan and all of my charging during weekdays occurs Midnight-8am. (The utility company supplied the charger/controller. I get a 60% discount on this TOU rate plan which results in $.07/KWH.) That means even if I plug in when I get home I am not applying any current for charging or conditioning the battery until midnight.

It would be nice to have some technical advice on the topic.

Or, maybe none of this really matters that much as long as the 80-20 rule is followed?

Thanks.

 

[DeaneG]

B) is not correct. A charging "cycle" is defined as charging through the total capacity of the battery. This could be 10 charges from 70% to 80% for example, or one charge from 0% to 100%. But the 0-100% version will age your battery faster.

Most long-time EV owners just set their max charge level to 80% and plug in every day. I'm retired without a daily commute, so I only plug in when the car gets below about 70%, which may take a few days to happen.

 

[ProdigalTrader]

ABC, with apologies to Glengarry Glen Ross, really means Always Be Charging.

Plug your car in every night at home, with a max charge of 80%, and you should have excellent battery life and health

 

[HariK]

ABC, with apologies to Glengarry Glen Ross, really means Always Be Charging.

Plug your car in every night at home, with a max charge of 80%, and you should have excellent battery life and health

You will know how much % per day your car uses based on your use. If you find out that in 1 week your use is 40%, I would just charge once a week when it hits 40%. No need to bother to plug in every single day after you come home.

 

[ProdigalTrader]

You will know how much % per day your car uses based on your use. If you find out that in 1 week your use is 40%, I would just charge once a week when it hits 40%. No need to bother to plug in every single day after you come home.

I disagree. Having owned a couple Model Ss over the past ten years, nightly charging is a very good habit to develop, especially for a newbie EV driver. Moreover, Musk has said in the past that it wouldn’t hurt, and BMW explicitly recommends it.

YMMV.

 

[joec]

You'll hear lots of conflicting advice on this matter. And lots of points of view from folks with more electrical knowhow, etc.

The best advice I can give is to not stress about it. Keep it between 20 and 80% most of the time. Top up to 100% when you really need to only. Then stop worrying.

It's actually pretty hard to damage one of these batteries, unless you are actively trying to damage it.

 

[stratus]

I plug in whenever I feel like it, usually not letting it go below 20 and stopping at 80.
I really cannot imagine there is compelling data that suggests a significant advantage when comparing sporadic charging versus daily charging ( using level 2 chargers ) , when examining battery life or overall performance, except for some possible small range advantage with keeping plugged in?

 

[BACamster]

I finally have my Lucid Air Touring (for one week) after waiting 9 months so I am now focused on topics I never paid attention to before. Today, I am obsessing about the optimal home charging regime with battery life in mind. I know there are multiple posting on this topic, so I apologize for the repetition, but the postings and debate still seem inconclusive to me.

Lucid says to plug in whenever not driving having something to do withy battery conditioning which I think matters in an environment of either hot (>80F) or cold (<40F) ambient temperatures. Obviously the 80-20 SoC rule holds, but the are multiple factors to consider and many different opinions abound. The opposing best practices I have heard are distilled to:

A.) Plug in and top off every night, however, max charge should be ideally 60% or 70% for optimal battery health, unless you need the range the next day then 80% is OK. Maintaining optimal battery temp is important for range and battery health so plug in which conditions the battery.

B.) Do not top off every night, battery life is driven by minimizing number of charging cycles even in the middle of the SoC range. Just plug in when in the 20-30% range.

Only one of these is directionally correct, subject to specifics.

Related question: Is there any battery conditioning happening after the charging cycle has ended and the charge limit has been reached, i.e., trickle charging?

As a sidebar, I have a time-of-use (TOU) rate plan and all of my charging during weekdays occurs Midnight-8am. (The utility company supplied the charger/controller. I get a 60% discount on this TOU rate plan which results in $.07/KWH.) That means even if I plug in when I get home I am not applying any current for charging or conditioning the battery until midnight.

It would be nice to have some technical advice on the topic.

Or, maybe none of this really matters that much as long as the 80-20 rule is followed?

Thanks.

Long time Tesla owner. Here are my answers to your questions:
A) Since you have TOU rate plan, set your AT charging limit to 80% for your daily usage and plugin your AT every night and schedule your AT to charge staring at 12:00AM
B) If you plugin every night, you should need to worry about the 20%-30% range.

 

[DeaneG]

I plug in whenever I feel like it, usually not letting it go below 20 and stopping at 80.
I really cannot imagine there is compelling data that suggests a significant advantage when comparing sporadic charging versus daily charging ( using level 2 chargers ) , when examining battery life or overall performance, except for some possible small range advantage with keeping plugged in?

There's quite a bit of data showing that smaller charging swings significantly improve cycle life. It's been studied extensively as it is a billion-dollar question for EVs, grid storage, etc. Here is a lay article:

BU-808: How to Prolong Lithium-based Batteries

BU meta description needed...

batteryuniversity.com

 

[stratus]

There's quite a bit of data showing that smaller charging swings significantly improve cycle life. It's been studied extensively as it is a billion-dollar question for EVs, grid storage, etc. Here is a lay article:

BU-808: How to Prolong Lithium-based Batteries

BU meta description needed...

batteryuniversity.com

View attachment 10770

Just finished reading this and THANK YOU for posting it. I can always count on learning new information here.

My daily trips are pretty short, about 15-20 miles a day. It sounds like good practice to keep the state of charge in a much narrower range than 20-80 % and I will start doing this tonight.

 

[Adnillien]

There's quite a bit of data showing that smaller charging swings significantly improve cycle life. It's been studied extensively as it is a billion-dollar question for EVs, grid storage, etc. Here is a lay article:

BU-808: How to Prolong Lithium-based Batteries

BU meta description needed...

batteryuniversity.com

View attachment 10770

To use the same total driving energy, you should compare the 85%-25% curve at a 1000 cycles and the 75%-65% curve at 6000 cycles. Both are about 93%. Smaller charges are better but you have to do them more often. If you compare based on equal driving energy, there is very little difference as long as you avoid very high SOC and very low SOC.

I agree with @joec, keep your battery at a reasonable SOC and spend time enjoying your car, not worrying about this. Charge the way that works best for you.

 

[SaratogaLefty]

Yeah so the 25/85 appears to have a 7% loss after 1000 cycles. If the average Lucid has a reliable full charge distance of 350 miles, then 60% (85% SOC minus 25% SOC) of that would be 210 miles. Each charging "cycle" then would provide over 200 miles of range. So if I'm reading this correctly and you charge up once a week (equates to about 10,500 miles driven per year which is higher than my average) that would mean you should still have around 93% battery capacity after 19 years. Is that a correct interpretation of the chart or am I way off base?

 

[stratus]

To use the same total driving energy, you should compare the 85%-25% curve at a 1000 cycles and the 75%-65% curve at 6000 cycles. Both are about 93%. Smaller charges are better but you have to do them more often. If you compare based on equal driving energy, there is very little difference as long as you avoid very high SOC and very low SOC.

I agree with @joec, keep your battery at a reasonable SOC and spend time enjoying your car, not worrying about this. Charge the way that works best for you.

Sometimes it’s simply a matter of remembering to plug in, depending on how catatonic I feel after getting home from work.

 

[Adnillien]

Yeah so the 25/85 appears to have a 7% loss after 1000 cycles. If the average Lucid has a reliable full charge distance of 350 miles, then 60% (85% SOC minus 25% SOC) of that would be 210 miles. Each charging "cycle" then would provide over 200 miles of range. So if I'm reading this correctly and you charge up once a week (equates to about 10,500 miles driven per year which is higher than my average) that would mean you should still have around 93% battery capacity after 19 years. Is that a correct interpretation of the chart or am I way off base?

Your interpretation is spot on.

 

[DeaneG]

To use the same total driving energy, you should compare the 85%-25% curve at a 1000 cycles and the 75%-65% curve at 6000 cycles. Both are about 93%. Smaller charges are better but you have to do them more often. If you compare based on equal driving energy, there is very little difference as long as you avoid very high SOC and very low SOC.

I agree with @joec, keep your battery at a reasonable SOC and spend time enjoying your car, not worrying about this. Charge the way that works best for you.

This and the other last few posts are not correct: a "cycle" is defined as the amount of charge to completely charge or discharge the battery (1C), not one charge of some smaller amount. One charge of 20% to 80% is 0.6 cycle. One charge of 0% to 100% is one cycle. A charge of 30% to 40% is 0.1 cycle. One cycle in my Air GT, for example, would be 112kWh of charge going into and out of the car's battery, or about 400 miles of freeway driving. I could do this one cycle by doing 100 charges from 50% to 51%, driving four miles after each charge, or one charge of 0% to 100%.

 

[DeaneG]

Each "cycle" corresponds to all the energy the battery can hold - all the miles you can drive on a single charge. So 1000 cycles would correspond to about 400,000 miles!

 

[Adnillien]

Each "cycle" corresponds to all the energy the battery can hold - all the miles you can drive on a single charge. So 1000 cycles would correspond to about 400,000 miles!

Maybe I am misreading it but this implies that a cycle is only the full energy in the battery when goiing from 100% to 0% SOC. This is from the article referenced above.

• Case 1: 75–65% SoC offers longest cycle life but delivers only 90,000 energy units (EU). Utilizes 10% of battery.
• Case 2: 75–25% SoC has 3,000 cycles (to 90% capacity) and delivers 150,000 EU. Utilizes 50% of battery. (EV battery, new.)
• Case 3: 85–25% SoC has 2,000 cycles. Delivers 120,000 EU. Uses 60% of battery.

 

[GMan]

There's quite a bit of data showing that smaller charging swings significantly improve cycle life. It's been studied extensively as it is a billion-dollar question for EVs, grid storage, etc. Here is a lay article:

BU-808: How to Prolong Lithium-based Batteries

BU meta description needed...

batteryuniversity.com

View attachment 10770

This is why my charging strategy is approx 75-45, which is the purple line. I don't plug every night because I'm not concerned about the phantom drain.

However, i don't drive daily so others may prefer to be charged at 80% everyday. Just understand that moves you to the right on the x-axis more rapidly.

 

[Steve F]

There's quite a bit of data showing that smaller charging swings significantly improve cycle life. It's been studied extensively as it is a billion-dollar question for EVs, grid storage, etc. Here is a lay article:

BU-808: How to Prolong Lithium-based Batteries

BU meta description needed...

batteryuniversity.com

View attachment 10770

Great data here in the chart from GMan. Before getting my Lucid Touring I had a Tesla Model S for almost 10 years. I too charged it every night and almost never above 75%. My wife has it now. I'm curious to see how long it will go.

 

[SaratogaLefty]

This and the other last few posts are not correct: a "cycle" is defined as the amount of charge to completely charge or discharge the battery (1C), not one charge of some smaller amount. One charge of 20% to 80% is 0.6 cycle. One charge of 0% to 100% is one cycle. A charge of 30% to 40% is 0.1 cycle. One cycle in my Air GT, for example, would be 112kWh of charge going into and out of the car's battery, or about 400 miles of freeway driving. I could do this one cycle by doing 100 charges from 50% to 51%, driving four miles after each charge, or one charge of 0% to 100%.

Okay Deane, that's even better. I was happy with the 19 years in my incorrect calculation above. But now with your correct information it is far greater than 19 years. So I will just continue to charge when my SOC gets down around 25% and charge up to 85% and not even begin to worry about battery degradation. I probably won't even charge once a week unless I'm doing a longer trip. I did read on another manufacturer's forum that their manual states it is good practice to charge up to 100% once a month or so as long as you don't let the car sit at that 100%. Also, apparently that manufacturer has a built in 5% buffer reserve so when you charge to 100% you are actually only charging to 95%. Not sure what buffer/reserve my Lucid has if any?? Also, not sure it really does make sense to charge to 100% once a month??