Charging below 50%

[SJRmylr]

I’ve learned a lot from AAKEE and a number of other users - one whose username I don’t recall, please chime in, but he mentioned he uses the stop charge function to usually charge up to only 35% and leave a 5% buffer at the end of the day.

So I’ve learned about calendar aging and cycle aging, and that for the first few years calendar aging is more significant, and that it’s better to store at low charge and charge before leaving.

I would like to know — assuming I use 15% a day, would it be advisable to charge to say 35% (or less) to aim to store at a low percentage.

Second question - let’s say I’ve finished my primary daily drive of 15% and the car is being stored at 20%. Now I have 5% worth of extra errands to run. Should I cycle deeper into the battery for this so I’m ultimately storing lower at 15% at the end of the day? Or should i pre charge for those extra errands so that im not cycling as deep but still stopping charge around 20-35% for calendar aging purposes.

I typically use 5-7% a day, and longer days are typically 15% - sometimes 20%.

So, I theoretically could get by with only charging to 25% and just add more when needed. I have a 2023 mylr with 8k miles and luckily it’s been charged to 50% on 120v for most of its life before I learned of AAKEEs postings that shows that 50% is not ldeal for rest like I had thought, but in fact lower is exponentially better until… very low.

If I’m only living with the battery at max 50%, should I prioritize ending the day with minimal battery SoC for calendar aging purposes, and cycle deeper in the battery to do this? It would probably take me about a week to cycle from 50%-10% if I pressed stop charging each time I plugged in that week.

My current take aways have been - disregard cycle aging for the first couple years and prioritize operating and storing the battery at minimal SoC.
With this line of thought I’m tempted to stop charging after plugging in, and only charge to 30 (or 25)% before departure, and only recharge when I’m depleted to say 7%. This would disregard cycling health and prioritize having the battery stored at minimal SoC, say under 10%. Is this plan of mine advisable?

Thank you

 

[GtiMart]

If you do want to play around and manage the charging very low, you're free to do so. I believe you're mostly splitting hairs at that point however. You could just set your charge target to 50% and plug when you feel you need to for the next day. OR you could even plug every day and let it go to 50%. It seems you're getting most of the gain as long as you stay below 55%.

 

[Pianewman]

OP: Splitting hairs, for sure, ANYTHING below 50% is going to be equally efficient and best for the battery.

 

[E90alex]

There is negligible benefit to micromanage the charge level to that point. If 50% works for you then just set it to that and forget about it.

The point of the low SOC strategy is to minimize degradation without inconveniencing yourself. Many people can stand to lower the charge limit without affecting how they use the car at all.

If you find pleasure in micromanaging the charging then that’s up to you. As long as you’re not going beyond 0% then you’re not harming the battery. Just remember the car limits functions once it gets below 20% and power gets reduced as well. And if your BMS gets out of calibration then the lower single digit % may not be accurate and could leave you stranded.

 

[SJRmylr]

There is negligible benefit to micromanage the charge level to that point. If 50% works for you then just set it to that and forget about it.

The point of the low SOC strategy is to minimize degradation without inconveniencing yourself. Many people can stand to lower the charge limit without affecting how they use the car at all.

If you find pleasure in micromanaging the charging then that’s up to you. As long as you’re not going beyond 0% then you’re not harming the battery. Just remember the car limits functions once it gets below 20% and power gets reduced as well. And if your BMS gets out of calibration then the lower single digit % may not be accurate and could leave you stranded.

Got it, I realize this is splitting hairs, I’m mostly just trying to understand how these batteries work just out of curiosity.

I have no interest in pushing below 20, and I will still charge to 80 for some weeks so I likely can manage a healthy BMS calibration. The biggest obstacle that I have is the 12 amp charging speed. Some weeks I’ll need to charge in advance to 80 just to keep up with that charge rate and my daily driving - but for the most part I’d say I’m averaging about 6% use per day, and occasionally not driven for a couple days in a row.

For reference I’m in Chicago doing mostly urban driving, with occasional 14 miles highways legs. Average temp is between 28 degrees F (today, winter) and 80F (summer) for anyone curious about that.

Two more questions.

First, does anyone know approximately how long is takes to warm the battery when it’s cold soaked to 32F (0C)?

Second, what’s the most efficient way to pre heat the cabin when using 12 amps? For example yesterday I charged for about 2 hours before departing, and turned on my cabin heater amount 20 mins before I left. In those 20 mins I used more energy than I had gained in the previous two hours of charging. Thanks.

 

[Darmie]

Hi. Welcome to TMC. Most have been said, not to worry to much. From the charts you can see that calendar aging is somewhat linear up to 55pct (50pct noted state of charge) It's ok to charge more as needed but storage according to chart is best 50pct or lower. I recommend using schedule charging so their for the car is not staying at a higher state of charge overnight. I typically charge to 60pct and use schedule charging. When the car is at work, the state of charge is around 45 to 47 pct the 11 hours. So, charge to what you need and use schedule charging so not to sit overnight at higher than needed SOC.

 

[jjrandorin]

Got it, I realize this is splitting hairs, I’m mostly just trying to understand how these batteries work just out of curiosity.

I have no interest in pushing below 20, and I will still charge to 80 for some weeks so I likely can manage a healthy BMS calibration. The biggest obstacle that I have is the 12 amp charging speed. Some weeks I’ll need to charge in advance to 80 just to keep up with that charge rate and my daily driving - but for the most part I’d say I’m averaging about 6% use per day, and occasionally not driven for a couple days in a row.

For reference I’m in Chicago doing mostly urban driving, with occasional 14 miles highways legs. Average temp is between 28 degrees F (today, winter) and 80F (summer) for anyone curious about that.

Two more questions.

First, does anyone know approximately how long is takes to warm the battery when it’s cold soaked to 32F (0C)?

Second, what’s the most efficient way to pre heat the cabin when using 12 amps? For example yesterday I charged for about 2 hours before departing, and turned on my cabin heater amount 20 mins before I left. In those 20 mins I used more energy than I had gained in the previous two hours of charging. Thanks.

I wouldnt be considering doing any of this micromanaging at all if I was charging on a 15amp connection (12amp charging), especially if I lived someplace that could actually get the battery cold soaked. If you want to do all that migromanaging you need to get a faster charging solution, or you run the very real possibility that your battery can get cold enough that you wont add any charge whatsoever from a 12v connection.

 

[SJRmylr]

I wouldnt be considering doing any of this micromanaging at all if I was charging on a 15amp connection (12amp charging), especially if I lived someplace that could actually get the battery cold soaked. If you want to do all that migromanaging you need to get a faster charging solution, or you run the very real possibility that your battery can get cold enough that you wont add any charge whatsoever from a 12v connection.

This has come to light, as my summer charging speed is twice the speed as I’m getting now. With that said I so far have not been held back by the charge speed with my low miles I’m driving. When I anticipate it is an issue I just charge to 55% or higher. I’m renting the garage so I can’t upgrade to level 2 for various reasons.

 

[jjrandorin]

This has come to light, as my summer charging speed is twice the speed as I’m getting now. With that said I so far have not been held back by the charge speed with my low miles I’m driving. When I anticipate it is an issue I just charge to 55% or higher. I’m renting the garage so I can’t upgrade to level 2 for various reasons.

Ok, but again, you run the very real risk that a 12amp connection could add ZERO charge, for a long period of time, because if it gets cold enough, all available power will go to heating the battery and never charge it, and that can happen for hours and hours (or longer, depending on how cold it actually gets).

Since you cant upgrade your charging solution, you shouldnt be playing "how low can I go" during the winter, with your charging. During spring / summer, sure, not now though, unless you have another vehicle you can rely on if you end up not being able to charge your car at all and need to go somewhere.

Anyway, good luck with whatever you decide.

 

[shahryaran]

The answer is simple:
Trade-off
Find a balance between maintaining battery health and practicality given the fact that some functions disables below 20% and in case of an emergency or some post-apocalyptic Mad Max Resident Evil stuff you have enough charge to get out of the city.

 

[SJRmylr]

Ok, but again, you run the very real risk that a 12amp connection could add ZERO charge, for a long period of time, because if it gets cold enough, all available power will go to heating the battery and never charge it, and that can happen for hours and hours (or longer, depending on how cold it actually gets).

Since you cant upgrade your charging solution, you shouldnt be playing "how low can I go" during the winter, with your charging. During spring / summer, sure, not now though, unless you have another vehicle you can rely on if you end up not being able to charge your car at all and need to go somewhere.

Anyway, good luck with whatever you decide.

Yes, the zero charge, so to avoid this I just don’t pre heat the cabin except for the heated seats. For me it works, with the girlfriend it’s charged to 50% and pre heated regardless of losses.

 

[jjrandorin]

Im not trying to "convince" you of anything, just inform you of what I have read from others here who charge in cold areas. Here are a few threads I linked to someone else asking about charging off 120v in cold areas.

If you saw these already, sorry for linking them again.

Not charging in cold?

I haven't had my Tesla connector installed yet so I'm just trickle charging at the new house that I'm at. Unfortunately I seem to be gaining "0 km/hr". Is this due to the cold (currently -15 Celsius) or is there another reason? Yesterday at the house it seemed fine.

teslamotorsclub.com

12A at 110V slow charging: 3% takes 7 hours

I have a mobile connector on a ~12A circuit which charges my Model Y from 70% to 80% in 4-6 hours. When I plugged it in tonight I noticed that it’ll take 7 hours to go from 77% to 80%. It still shows 12A at 110V. Everything plugged in correctly. Any thoughts?

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‘22 MY in ultra sub cold tips?

Hey Now! In Colorado and bracing for the cold snap. It’s supposed to drop over 50 degrees today (down to -8 without wind chill)…reminds me of the Day After Tomorrow movie. I’ve been thinking about leaving the climate control on with the car plugged in of course. Any other tips for this cold...

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[SJRmylr]

The answer is simple:
Trade-off
Find a balance between maintaining battery health and practicality given the fact that some functions disables below 20% and in case of an emergency or some post-apocalyptic Mad Max Resident Evil stuff you have enough charge to get out of the city.

Ok, but again, you run the very real risk that a 12amp connection could add ZERO charge, for a long period of time, because if it gets cold enough, all available power will go to heating the battery and never charge it, and that can happen for hours and hours (or longer, depending on how cold it actually gets).

Since you cant upgrade your charging solution, you shouldnt be playing "how low can I go" during the winter, with your charging. During spring / summer, sure, not now though, unless you have another vehicle you can rely on if you end up not being able to charge your car at all and need to go somewhere.

Anyway, good luck with whatever you decide.

For me so far in 15f the worst so far I’ve experienced is about 5 hours of the battery gaining no charge and just warming it’s self after that it has in my experience returned more or less to a 5 mph rate. But this is a side topic that I’ll explore this winter as it gets colder, and I assure you all I won’t be hovering the SoC low when the temps are especially cold.

 

[tga]

If you're charging on 120V in winter where it gets really cold (like Chicago), you should plug in and start charging as soon as you get home, every time you get home to take advantage of the already-warmed battery.

 

[SJRmylr]

Thanks that’s great feedback and I have started doing this. It takes a couple hours at 30% efficiency before the charge rate speeds up if I let the battery cool to ambient, say 0-15F

 

[tga]

Thanks that’s great feedback and I have started doing this. It takes a couple hours at 30% efficiency before the charge rate speeds up if I let the battery cool to ambient, say 0-15F

The real problem is that during the time the battery is heating, much of the power is coming from the battery itself (since 120V/12A power is so limited), so it will discharge somewhat before it starts charging up again. If you're starting at a low state of charge, things could get ugly if there isn't enough capacity remaining to warm the battery enough to start charging.

 

[SJRmylr]

That makes sense

 

[LostVector]

I’ve learned a lot from AAKEE and a number of other users - one whose username I don’t recall, please chime in, but he mentioned he uses the stop charge function to usually charge up to only 35% and leave a 5% buffer at the end of the day.

So I’ve learned about calendar aging and cycle aging, and that for the first few years calendar aging is more significant, and that it’s better to store at low charge and charge before leaving.

I would like to know — assuming I use 15% a day, would it be advisable to charge to say 35% (or less) to aim to store at a low percentage.

Second question - let’s say I’ve finished my primary daily drive of 15% and the car is being stored at 20%. Now I have 5% worth of extra errands to run. Should I cycle deeper into the battery for this so I’m ultimately storing lower at 15% at the end of the day? Or should i pre charge for those extra errands so that im not cycling as deep but still stopping charge around 20-35% for calendar aging purposes.

I typically use 5-7% a day, and longer days are typically 15% - sometimes 20%.

So, I theoretically could get by with only charging to 25% and just add more when needed. I have a 2023 mylr with 8k miles and luckily it’s been charged to 50% on 120v for most of its life before I learned of AAKEEs postings that shows that 50% is not ldeal for rest like I had thought, but in fact lower is exponentially better until… very low.

If I’m only living with the battery at max 50%, should I prioritize ending the day with minimal battery SoC for calendar aging purposes, and cycle deeper in the battery to do this? It would probably take me about a week to cycle from 50%-10% if I pressed stop charging each time I plugged in that week.

My current take aways have been - disregard cycle aging for the first couple years and prioritize operating and storing the battery at minimal SoC.
With this line of thought I’m tempted to stop charging after plugging in, and only charge to 30 (or 25)% before departure, and only recharge when I’m depleted to say 7%. This would disregard cycling health and prioritize having the battery stored at minimal SoC, say under 10%. Is this plan of mine advisable?

Thank you

I would recommend minimizing the depth of discharge. Just charge shallow every day. You are driving it daily, so if you alter your DoD, that will have a dominant effect on the battery's lifetime.

Did you know that the anode of the battery literally physically expands by about 10% when fully charged? These physical stresses obviously degrade the battery. I find once someone understands this, they more viscerally understand why higher DoD's are bad for the battery. It is not worthwhile to increase a daily DoD in order try and lower calendar aging.

 

[LostVector]

I would recommend minimizing the depth of discharge. Just charge shallow every day. You are driving it daily, so if you alter your DoD, that will have a dominant effect on the battery's lifetime.

Did you know that the anode of the battery literally physically expands by about 10% when fully charged? These physical stresses obviously degrade the battery. I find once someone understands this, they more viscerally understand why higher DoD's are bad for the battery. It is not worthwhile to increase a daily DoD in order try and lower calendar aging.

Adding this screenshot from a well known YT video on EV battery life to support the above.

 

[fhteagle]

Engineering Explained re-statement of Dahn, other studies, etc. Skips some details, but would be a good intro to the subject.

To OPs original question, a higher number of smaller DOD cycles is better than fewer deeper chargers in most cases. So