So Why Does It Matter Keeping Tesla Battery Between 20%-80% Charged?

[xyeahtony]

sure @calvinvle disagree with my post without saying why, never mind that everything stated was factual and confirmed with a link and multiple sources.

 

[timk225]

Anyone have a chart showing the voltage per cell at what Tesla deems to be 0%, 10%, 20%, all the way to 100%? And what are the high and low safe voltage limits of lithium ion cells with the particular Tesla chemistry?

Would it be safe to say that as long at the car gets charged enough overnight to do what you need to do the next day, the slowest charging rate is always better for the battery? So charging from a 6-20 outlet would be better (for the battery) than charging from a 14-50? And charging from a 5-15 would be better than any other voltage or amperage commonly available?

 

[Rocky_H]

Would it be safe to say that as long at the car gets charged enough overnight to do what you need to do the next day, the slowest charging rate is always better for the battery? So charging from a 6-20 outlet would be better (for the battery) than charging from a 14-50? And charging from a 5-15 would be better than any other voltage or amperage commonly available?

No, it might seem that way, but that's actually not true. I've seen a paper on this, but can't find it now. As with many things, moderation is best. There are degradation and damage issues with both very fast and very slow charging. The fast effect we know about, because it creates huge amounts of heat, which is bad for the battery. The problem at the very slow end is that there is a different kind of low level minor damage to the cells which is based on the amount of time it is in the state of being charged. (Some kind of metal plating effect I think?) And if you can just get the charge done with sooner and let it get back to sitting, that is better for it. So if you use a very low charging power that makes the charging time take 10X longer, you are keeping it in that slightly damaging charging operation for longer. Also, remember this isn't just about your battery. You are keeping the onboard charger running for much longer times, too, so you're kind of running through its useful lifetime faster as well.

 

[drawfour]

I'm going to charge to 70%. 70% of 310 miles is 217 miles. I'll get the same range as a 100% charged SR, and can top it up to 95-100% for road trips.

That or I'll just go with whatever the Tesla dude recommends.

 

[Quickstart88]

Because 50% is the sweet spot for the battery, and because I use about 20% of the battery each day, I charge to 60% overnight. That way the highest I get is 60% and the lowest I get is 40%, which is right in the middle of that 50% sweet spot. Like others have been saying, of course I charge to 100% if I have a roadtrip the next day.

Yup - I drive 30 miles a day. I keep my between 150 miles to 200 miles. Right in the 50% ish range where Lithium wants to be.
A 45 mins charge to an hours will give me ~ 28 to 30 miles charge. The only thing I haven't figured out is how much does it cost me to charge for an hour that give me 28 to 30 miles? I am using the mobile UMC which is a 32 amps connected to a Nema 14-50 plug 50 amp breaker.
My electric bill is per kilo watt hour is 25 cents. Does that means it cost me 25 cents to charge my car for an hour and give me 28 to 30 miles ranges?

Anyone know how this work?

My ICE takes 16 miles to the gallon. That's two gallons on average I use a day at $3.50 ish per gallon. That's 7 bucks on day on gas.
What is my cost in terms of electricity.

 

[MorrisonHiker]

Yup - I drive 30 miles a day. I keep my between 150 miles to 200 miles. Right in the 50% ish range where Lithium wants to be.
A 45 mins charge to an hours will give me ~ 28 to 30 miles charge. The only thing I haven't figured out is how much does it cost me to charge for an hour that give me 28 to 30 miles? I am using the mobile UMC which is a 32 amps connected to a Nema 14-50 plug 50 amp breaker.
My electric bill is per kilo watt hour is 25 cents. Does that means it cost me 25 cents to charge my car for an hour and give me 28 to 30 miles ranges?

Anyone know how this work?

My ICE takes 16 miles to the gallon. That's two gallons on average I use a day at $3.50 ish per gallon. That's 7 bucks on day on gas.
What is my cost in terms of electricity.

32 amps × 240 volts = 7680 Watts
7680 Watts ÷ 1000 Watts/kW = 7.68 kW
7.68 kW/hour × $0.25/kW = $1.92/hour

 

[EV-lutioin]

Yup - I drive 30 miles a day. I keep my between 150 miles to 200 miles. Right in the 50% ish range where Lithium wants to be.
A 45 mins charge to an hours will give me ~ 28 to 30 miles charge. The only thing I haven't figured out is how much does it cost me to charge for an hour that give me 28 to 30 miles? I am using the mobile UMC which is a 32 amps connected to a Nema 14-50 plug 50 amp breaker.
My electric bill is per kilo watt hour is 25 cents. Does that means it cost me 25 cents to charge my car for an hour and give me 28 to 30 miles ranges?

Anyone know how this work?

My ICE takes 16 miles to the gallon. That's two gallons on average I use a day at $3.50 ish per gallon. That's 7 bucks on day on gas.
What is my cost in terms of electricity.

It depends on your electricity rate and the tier you are using, but in general, folks consider the cost of electricity to be about the equivalent of $1/gal.

Edit: just saw that you posted your electricity rate. That seems high, have you looked into PG&E's EV rate for .09 kWh?

 

[Quickstart88]

It depends on your electricity rate and the tier you are using, but in general, folks consider the cost of electricity to be about the equivalent of $1/gal.

25 cents is tier two rate for me. In looking at my bill I am using 16 kilowatt hr per day on average. With the addition of EV charging every night for ~ 1 hours. I haven't figure out how much kilowatt hr it take to charge my car for 1 hours. I figure each kilo watt hr is 25 cents.

I also heard electricity is 1/3 the price you pay in contrast to gasoline.

 

[Quickstart88]

32 amps × 240 volts = 7680 Watts
7680 Watts ÷ 1000 Watts/kW = 7.68 kW
7.68 kW/hour × $0.25/kW = $1.92/hour

Nice - Thanks! So ~ $ 1.92 vs 7 bucks a day.

 

[jamnmon66]

You'll get around 4 miles per KWH depending on driving habits. This doesn't include efficiency losses when charging but it's probably close enough for an estimate. So, if you pay .25 per KWH then you're paying roughly .25 for every 4 miles driven.

Surprised to see such a high rate. I pay .06 per KWH off-peak.

 

[Graffi]

In a Nissan Leaf, or a Tesla Model 3, you can get 4 miles per kWh (250 Wh/mile), but in a Tesla Model S you can plan on 3 miles per kWh (333 Wh/mile).

At $0.25 per kWh the cost per mile and 30 mile daily drive would be:

Tesla Model 3: $0.0625 per mile or $1.875 for 30 miles daily.

Tesla Model S: $0.08325 per mile or $2.4975 for 30 miles daily.

 

[Tozz]

The problem at the very slow end is that there is a different kind of low level minor damage to the cells which is based on the amount of time it is in the state of being charged. (Some kind of metal plating effect I think?)

Do you have any links that support your statement? I have never heard of this regarding slow charges. I have heard of metal plating when you overcharge the battery, or when charging below freezing temperatures (note: Tesla will warm your battery, so this is a non-issue) not when you charge it slowly

 

[Rocky_H]

Do you have any links that support your statement?

I said when I posted that comment: "I've seen a paper on this, but can't find it now." It had charts in it showing lifetime capacity degradation over many cycles for a broad range of charging behaviors, from very low power for extremely long times, to very high power for short times. And it was one of those bimodal graphs that goes exponential on the ends with more damage from both extremes, and it explained about the degrading effects of being in the charging process for really long extended periods of time instead of getting it over with in a reasonable amount of time and letting it rest.

It's just not a very common topic, because really, who is interested in recharging anything with batteries as slow as possible?! We all want to recharge everything as fast as we can get away with. So that effect isn't talked about much because no one is interested in it, so I've only seen it that one time I think, and I wasn't able to find that paper again from looking through a few pages of the search results I could come up with, so it wasn't worth spending more of my effort on.

 

[LSE47]

well this is a very illuminating thread. When i picked up the model 3, the tesla folks told me to charge it every night and that the battery works best being kept near full charge. I have an 80 mile daily commute and have been charging to 90% (282m) most evenings. I installed the Tesla wall charger since i didn't have a 220 line in the garage. Based on reading this thread, i could charge to 80% and run it down to 30% over 2 days of commuting and that would be better for battery life

Is routinely charging with max amps also to be avoided? considering i can keep the car overnight on the charger, what is a good amperage to charge at?

 

[TexasEV]

Just keep doing what you’re doing. If you RTFM (the battery section), you will see that Tesla recommends plugging in whenever you can. There is no advantage to letting the battery run down before charging. And the max 48A of AC charging is trivial compared to supercharging.

Don’t obsess over the battery. The battery will be just fine. Don’t slow down the rate. Don’t charge less often. Just plug in whenever you get home and let the battery management system manage the battery.

 

[Tozz]

It's just not a very common topic, because really, who is interested in recharging anything with batteries as slow as possible?! We all want to recharge everything as fast as we can get away with.

Well, for the simple reason I'm charging as slow as I can (3 kW) to have less degradation. I'm planning on owning the car for a long time.
Besides that, there is no reason for me to charge faster. 3 kW is more than plenty for me. My commute is less than 30 miles. It also saves some heat which means less lost energy, might also prevent the battery cooling to turn on (again, saving energy). So all in all its more efficient, cheaper and less harmfull to the battery.

I'm even thinking of getting a single phase charge cable so I can charge at 1 kW

I did some extensive Googleing after i read your post, but i cannot find anything that supports your statement.

I just want to get the truth out about batteries

 

[gregincal]

well this is a very illuminating thread. When i picked up the model 3, the tesla folks told me to charge it every night and that the battery works best being kept near full charge. I have an 80 mile daily commute and have been charging to 90% (282m) most evenings. I installed the Tesla wall charger since i didn't have a 220 line in the garage. Based on reading this thread, i could charge to 80% and run it down to 30% over 2 days of commuting and that would be better for battery life

Is routinely charging with max amps also to be avoided? considering i can keep the car overnight on the charger, what is a good amperage to charge at?

I think you misread the thread. There is absolutely no advantage to only charging every other day. You want to minimize extremes of battery charge, not artificially make them greater by running the battery down more. You would be better off charging to 70% and charging every day, although charging to 80% every day would be fine too.

 

[TexasEV]

Well, for the simple reason I'm charging as slow as I can (3 kW) to have less degradation. I'm planning on owning the car for a long time.
Besides that, there is no reason for me to charge faster. 3 kW is more than plenty for me. My commute is less than 30 miles. It also saves some heat which means less lost energy, might also prevent the battery cooling to turn on (again, saving energy). So all in all its more efficient, cheaper and less harmfull to the battery.

I'm even thinking of getting a single phase charge cable so I can charge at 1 kW

You’re deluding yourself. The car charges at over 100 kW when supercharging, so do you really think there’s a meaningful difference to the battery if it sees 3 kW vs 6 kW? On the other hand, slower charging means the charging system runs much longer, so more strsss on those components, and you use more electricity because the charging is less efficient.

Most of us who have owned a Tesla from the early Model S days will tell you to stop obesssing over the battery and just enjoy the car.

 

[SigNC]

well this is a very illuminating thread. When i picked up the model 3, the tesla folks told me to charge it every night and that the battery works best being kept near full charge. I have an 80 mile daily commute and have been charging to 90% (282m) most evenings. I installed the Tesla wall charger since i didn't have a 220 line in the garage. Based on reading this thread, i could charge to 80% and run it down to 30% over 2 days of commuting and that would be better for battery life

Even better, would be to just charge it to 70% and plug in when you get home everyday. Minimally better but still better.

 

[Rocky_H]

Well, for the simple reason I'm charging as slow as I can (3 kW) to have less degradation. I'm planning on owning the car for a long time.
Besides that, there is no reason for me to charge faster. 3 kW is more than plenty for me. My commute is less than 30 miles. It also saves some heat which means less lost energy, might also prevent the battery cooling to turn on (again, saving energy). So all in all its more efficient, cheaper and less harmfull to the battery.

None of that is less harmful to the battery, as @TexasEV already mentioned. The car uses over 100kW rates for recharging, so any single digit kW levels of 9 or 7 or 3 are already so low that there just won't be any noticeable difference to the battery. As far as less heat and less lost energy, again, you're not thinking it through. There is some overhead energy usage in running the charging system. You are running that charging circuit double, triple, quadruple the amount of time, wasting greater and greater amounts of energy. There is a small nugget of truth about heat, but it's not really related to the battery. Sometimes the charging cables are made to handle up to a certain amount of maximum current. So their conductors and connections are sized to barely handle that level, and they can get a little hot running at maximum level. Some of the wall connectors running at maximum 80A or the old mobile charge cables running at maximum 40A had some heat problems running at max all the time. So turning them down a little bit does help keep them a little cooler, and there is less extreme hot/cold temperature cycling from daily use, putting materials strain on the solder joints and electronics, etc.

I did some extensive Googleing after i read your post, but i cannot find anything that supports your statement.

I just want to get the truth out about batteries

I don't really care if you have seen the article I read about it. I've read it, and there's no real point or advantage to charging extra extremely slowly, so I'm not going to do it. You can feel free to charge as badly as you want to, though.