Ok to routinely charge from 45-50% SOC to 57% SOC

[mmanner]

I have a MS 100D acquired 4/2017. I charge to 90% when I head out on a road trip with Supercharging on the road, but when not going on a trip, which is most of the time, I have the max charge set to 57%. Some days I only drive 10 or 20 miles, other days 50 or 60. I plug in to my HPWC every night, so I frequently end up charging just a few % points. I have read that the mid-50% range is a nice spot to keep the battery SOC if you don't usually need any more, and that between 20-80% the lion batteries are more or less linear in accepting and putting out electrons. Is there any problem in charging just a few percentage points in the 50% range on a daily basis?
Thanks,
Mark

 

[SageBrush]

No problem

 

[TexasEV]

No problem, but you're treating yourself more than the battery. Totally not necessary. Just set it at 80 or 90% and forget it. And start your trips at 100%. That's what it's there for.

 

[mmanner]

Hi, you are right about this mostly being about treating myself. I had a Leaf for several years and was compulsive about charging to no more than 80%. In the Leaf's case, I frequently ran it down to 10 -15% given the very modest range it had, so I was charging from 15-20% to 80% almost daily. It is a treat to have a BEV with the range of the MS 100D.

 

[gregd]

I have a MS 100D acquired 4/2017. I charge to 90% when I head out on a road trip with Supercharging on the road, but when not going on a trip, which is most of the time, I have the max charge set to 57%. Some days I only drive 10 or 20 miles, other days 50 or 60. I plug in to my HPWC every night, so I frequently end up charging just a few % points. I have read that the mid-50% range is a nice spot to keep the battery SOC if you don't usually need any more, and that between 20-80% the lion batteries are more or less linear in accepting and putting out electrons. Is there any problem in charging just a few percentage points in the 50% range on a daily basis?
Thanks,
Mark

As long as you do get the battery up above 80% once in a while, you should be ok, if a little obsessive.

The issue if you never (or rarely) get the battery more fully charged is that the cells will slowly get out of "balance", which will give you a less accurate estimate of range.

 

[GSP]

Sounds like ideal battery usage to me. Not sure if 57% is any better than 80-90% however. It might be, but most sources indicate no difference.

I charge mine to 80% every night. That way if I need to go out of town unexpectedly, I would normally have the charge I need. Even if I do need 100%, it takes less time to get there from 80% than from 50.

GSP

 

[mal_tsla]

Tesla says that 100% in their batteries equals 4.15V, or 95% of the actual battery max. The blog post below is pretty informative:

A Bit About Batteries

90% Tesla charge amounts to a battery charge of 4.1V. This is well within the "long life" voltage range for a battery of this type.

Charging to 50% (3.8V) may actually be worse if you end up driving at a low SOC (below 3.2V is battery stressing) when you didn't need to.

We charge to 90% any time the car is in the garage and 100% an hour or two before a trip departure.

Tesla has already set these sliders up with battery preservation as the priority.

 

[apacheguy]

One study said that Li batteries should routinely be charged above 3.92 V to prevent dendrite formation on the anode. No idea whether it holds true for Teslas cells.

 

[apacheguy]

Tesla says that 100% in their batteries equals 4.15V, or 95% of the actual battery max. The blog post below is pretty informative:

A Bit About Batteries

90% Tesla charge amounts to a battery charge of 4.1V. This is well within the "long life" voltage range for a battery of this type.

No. 100% is 4.2 V in my 85 kWh. But yes, 90% is slightly under 4.1 V.

 

[David99]

It's perfectly fine for the battery and good as well for longevity. I disagree that it 'makes no difference' and just charge to 90% all the time. It does make a big difference in battery life if you only charge to 50 or 80/90%. If you don't need the range, keep the battery level low. If you go on trips, charge to 100%, that's perfectly fine because you are driving right after you charge so the time spent at 100% is very short. Charge to 100% here and there for a trip is far less harmful than charging to 90% daily instead of 50% or 60%.

 

[TexasEV]

It's perfectly fine for the battery and good as well for longevity. I disagree that it 'makes no difference' and just charge to 90% all the time. It does make a big difference in battery life if you only charge to 50 or 80/90%. If you don't need the range, keep the battery level low. If you go on trips, charge to 100%, that's perfectly fine because you are driving right after you charge so the time spent at 100% is very short. Charge to 100% here and there for a trip is far less harmful than charging to 90% daily instead of 50% or 60%.

Where is your data for "a big difference in battery life" with regard to the Model S and X? The only data I've seen people cite are generic studies, not Tesla's battery with the temperature controlled battery management system. My data point is I've only lost 4% of range in 4 years by charging to 90% routinely, and 100% a few times/month for trips (my 60 has 200 miles range fully charged vs. 208 miles when new in 2013). I don't think anyone has significantly less loss of range by only charging to 50%. You're not going to do better than 4% in 4 years. And so what if it's 3% by charging less? Does 2 miles really matter?

 

[brkaus]

I've set my S100D on 80% and charge nightly. I can easily meet all my daily needs. If I need to leave town in a hurry, I can still make it to a SpC in each direction. And it only takes a few hours to get it up 100% as another option.

 

[David99]

Where is your data for "a big difference in battery life" with regard to the Model S and X? The only data I've seen people cite are generic studies, not Tesla's battery with the temperature controlled battery management system. My data point is I've only lost 4% of range in 4 years by charging to 90% routinely, and 100% a few times/month for trips (my 60 has 200 miles range fully charged vs. 208 miles when new in 2013). I don't think anyone has significantly less loss of range by only charging to 50%. You're not going to do better than 4% in 4 years. And so what if it's 3% by charging less? Does 2 miles really matter?

Tesla's batteries are not something fundamentally different. There are countless studies that Lithium batteries degrade faster when at 90% than at 50%. That's exactly why Tesla allow the slider down to 50%. It's awesome you lost only 4% over 4 years, but a single data point without knowing what would have happened had you only charged to 50% is not a counter argument to all these studies. A battery in a car is subject to all kind of variables that affect life so it is really hard, if not impossible, to make a statement what affected battery degradation and what did not, let alone how much each factor did. So I think it's fair to go with the studies that keep all other factors constant and prove that degradation is accelerated when the battery is at a higher level of charge.

 

[mal_tsla]

I guess I'm done here when someone tells me Tesla themselves doesn't know what voltage 100% charge equates to in their own battery pack. Or maybe you've taken the cells out and put a volt meter on them?

Furthermore Tesla absolutely does have their own specialized battery chemistry. Lithium ion batteries are not all the same. Check out any of Jeff Dahn's brilliant work, most recently as a consultant for Tesla.

¯\_(ツ)_/¯

 

[David99]

I guess I'm done here when someone tells me Tesla themselves doesn't know what voltage 100% charge equates to in their own battery pack. Or maybe you've taken the cells out and put a volt meter on them?

Furthermore Tesla absolutely does have their own specialized battery chemistry. Lithium ion batteries are not all the same. Check out any of Jeff Dahn's brilliant work, most recently as a consultant for Tesla.

¯\_(ツ)_/¯

Jason Hughes as taken battery packs apart and confirmed that Tesla is charging the cells to 100% when the slider is set to 100%. At 0% there is some energy left in the battery though. So 0% shown in the car is not truly a fully discharged battery cell. That would be damaging. But 100% is 100% according to people that know something about batteries and have tested the cells from the packs.

 

[mal_tsla]

So the blog post above is Tesla lying ?

 

[thecloud]

So the blog post above is Tesla lying ?

No, but since that blog post is 11 years old and was specifically about the batteries used in the Roadster, I'm willing to entertain the idea that some small improvements may have been made in the years since it was written.

 

[TexasEV]

Tesla's batteries are not something fundamentally different. There are countless studies that Lithium batteries degrade faster when at 90% than at 50%. That's exactly why Tesla allow the slider down to 50%. It's awesome you lost only 4% over 4 years, but a single data point without knowing what would have happened had you only charged to 50% is not a counter argument to all these studies. A battery in a car is subject to all kind of variables that affect life so it is really hard, if not impossible, to make a statement what affected battery degradation and what did not, let alone how much each factor did. So I think it's fair to go with the studies that keep all other factors constant and prove that degradation is accelerated when the battery is at a higher level of charge.

Yes there may be a measurable difference. That doesn't mean the difference is meaningful in driving a Model S. There's a difference between statistically significant and clinically meaningful effects, an analogy that all physicians on this board will recognize.

 

[Rocky_H]

I do think it's a little funny when Tesla specifically recommends on the battery meter to NOT use the 90-100% range for constant daily use, but people still think 90% is perfect. Why would 90% be good, but 91% be bad? That doesn't even pass the sniff test. So yeah, that's why many people realize the principle and use around 75-80% for daily use to get it a little bit farther away from the un-recommended high end.

 

[SageBrush]

I do think it's a little funny when Tesla specifically recommends on the battery meter to NOT use the 90-100% range for constant daily use, but people still think 90% is perfect. Why would 90% be good, but 91% be bad? That doesn't even pass the sniff test. So yeah, that's why many people realize the principle and use around 75-80% for daily use to get it a little bit farther away from the un-recommended high end.

Good point, although the effect is far from linear.