100% charge ?

[solarjk]

I used to charge to 100%. Before a long trip or to balance the battery, maybe once a month.
Given the Kona's and Bolt's issues, I am wondering if I should still do it?

I know I have an SK Innovations battery pack, which is not LG.

Under normal times, I charge to 70% in summer. Plug in at 35%. in winter, I charge to 80%

 

[Kia Guy]

Charging your car up to 100%, especially if you're only doing so on occasion, is absolutely fine.

My Kia dealer actually told me that charging to 100% regularly is completely fine. Though I think Kia HQ have since changed this stance.

 

[ENirogus]

I think people are reading the wikipedia page on lithium batteries and extrapolating to cars.
You cannot charge your car to 100 percent, the BMS won't let you.
I don't believe the owners manual says anything about not charging to [indicated] 100 percent
If you plan on keeping your car for 20 years and 300k miles, there might be an advantage to more advanced battery management.
Maybe
I think not draining it below 20 percent is probably more relevant to battery life.

 

[David T in Silicon Valley]

Lithium ion chemistry can make a bit of a difference, but most LiIon batteries will behave more or less the same.What will make a difference is battery management in the device that is invisible to the user. For instance, in iOS 13 and up, the phone has a built in hysteresis for the batter near the top end if it has not been moved in a while. This reduces wear on the battery from leaving it plugged in all night near 100% with zillions of tiny chargé cycles as it drains a touch, charges up, drains a touch again, charges up etc. Makes a big difference in battery life.

The Niro EV has an extra 3ish (3.4?) kWh in the battery pack that the user does not access. This increases battery life by avoiding it charging all the way up until there has been some degradation reducing capacity.

I would not worry about charging to 100% so the system can calibrate what full looks like. I suspect there are good current meters built into the electrical system to track how much is going in and coming out and comparing against cell voltage to get a read on capacity.

There is great write up out of BU on cycling.
https://batteryuniversity.com/article/bu-808-how-to-prolong-lithium-based-batteries

The plot comes form a study of cells used in some electric vehicles in Europe. They cycled batteries thousands of times between different levels. It is a little tricky to read since you have to think in terms of kWh per cycle to get a sense on capacity as function of miles on the vehicle.

These forums have these two threads on the topic, Read and decided what is right for you.

https://www.insideevsforum.com/community/index.php?threads/maximizing-battery-life.5710/

https://www.insideevsforum.com/community/index.php?threads/increasing-battery-life.8644/#post-97749


My conclusion is if you don't mind being down to 70% capacity by the time you hit 200k , sure, charge to 100% all the time. As for me, I am nursing my battery from ~35%-80% except when I need the extra range. I also don't stress too much if I bust out of that range from time to time for whatever reason.

I intend my range to outlast the rest of the car....

 

[ENirogus]

Cars last until something expensive dies that is worth more than the car is. Cars get towed to the junkyard that look perfect because it is a 1500 dollar car with a bad transmission that costs 1600 dollars to fix.
Or they get beat up through accidents and just 'life' and end up worth more as parts.
A fraction of these cars will hit 200k, through no real fault of their own.
Worrying about what happens then is IMHO pointless.

I still don't see extensive evidence that charging to 100 percent degrades a modern managed battery
Rapid charging, running very low, these are known issues, but charging to the manufacturers recommendation is not something that one should worry about. I personally will be charging less than once a week on average, since battery life is strongly related to charging cycles, how long until I hit 'x' thousand cycles?

My only caveat is that I plan to keep the car plugged in all winter[when it gets more use anyway] and I may use my 120 volt cable so it is not kept at 100 percent all the time. 'Keeping' a battery at 100 percent is probably 'bad'

 

[DrHops]

I have a good friend who is a partner in a commercial car charger company. He told me that charging at home to 100% will not hurt or degrade the battery due to the built in buffer. He did warn against doing this at fast chargers though.

 

[Seagull]

The key to long HV battery life is not over heating or "freezing" the battery. Charging causes the battery temp to increase. Fast DC charging causes the battery to heat up faster and even faster as the SoC approaches 100%. AC charging does seem to increase the battery temp as much. Most, if not all, newer EV have a BMS that will cool the battery as you are charging but will not continue to cool the battery when it is turned off or not charging. This is the main reason it is recommended not to charge 100% and leave it unused. The built-in buffer helps to prevent this so it may not be as critical as it used to be.

I have not read any studies that give a fixed temperature for what is too cold but it looks it is some where around 15 or 20 degrees below freezing. Both high and very low temps degrade the battery chemistry.

The Battery University (as referenced by David T) seems to provide the most reasonable and creditable information.

As for me, I charge my Niro to a maximum of 80% unless I need the extra range and once every month or two I charge to 100% to equalize the battery and calibrate the BMS just before a longer trip. When possible I try to charge before I reach 40% except road trips where I go down to around 10%. I have 26,000 kM on my 2019 and my Battery health is still 100%.

 

[ENirogus]

Battery life is generally defined by charge recharge cycles.
IF you and I both 10k miles a year, and you charge to 80 percent and I charge to 100 percent, and we both recharge when we hit 20 percent:

You will have 69 charge cycles per year.

I will have 52 charge cycles per year.

So I don't know if that is actually a win or not.
I still think this whole 80 percent thing is wikipedia knowledge.
Tesla allows the most 'battery abuse' of the major carmakers, and their battery degradation numbers are pretty good, so, I am choosing to not worry about it.

 

[Hedge]

Battery life is generally defined by charge recharge cycles.
IF you and I both 10k miles a year, and you charge to 80 percent and I charge to 100 percent, and we both recharge when we hit 20 percent:

You will have 69 charge cycles per year.

I will have 52 charge cycles per year.

So I don't know if that is actually a win or not.
I still think this whole 80 percent thing is wikipedia knowledge.
Tesla allows the most 'battery abuse' of the major carmakers, and their battery degradation numbers are pretty good, so, I am choosing to not worry about it.

If you both drive the same mileage, and have the same efficiency then the amount of cycles would be the same. If you each use 10% a day you will charge every 8 days and he will charge every 6 days. Every 48 days each of you will have charged 4.8 cycles.

A charge cycle isnt every charging session. It is 100%-> 0%-> 100%. Even if it is 80%->70%->80% it would take 10 charging sessions to be a single cycle.

 

[R P]

A charge cycle isnt every charging session. It is 100%-> 0%-> 100%. Even if it is 80%->70%->80% it would take 10 charging sessions to be a single cycle.

Is that really true? I have no reason to doubt that, but would like to see some sources that support that?

 

[solarjk]

I have a Niro EV with just about 30K on it.

For comparison, I also have a Tesla Powerwall II which I lease from my utility and they and Tesla control it. It has some thing like 13+kwh storage and the maximum draw is 5 Kw It usually sits at 100%, and when there is a system-wide peak, they often draw it down at the max rate until it hits 0%. Tesla warrants battery to ten years and I pay $ 15.00 a month for ten years ( $ 1800 ) and I can keep it for fifteen years unless Tesla/utility wants its back. So there are a lot ways to manage a battery. If there is a storm coming, they usually leave at 100%, which given my usage, would give me a two or three days of usage. I also have a 3.1 Kw PV system, which provides me with 80% of my electric, even with car charging.

 

[David T in Silicon Valley]

You will have 69 charge cycles per year.

I will have 52 charge cycles per year.

So I don't know if that is actually a win or not.

Rescale the Y axis to kWh (And that scale will be different depending on the the delta between start and finish state of charge; the scales would be the same comparing say the 100%-40% to the 85%-25% curves) and integrate under the curves in the plot in the Battery U article I linked up there you will see less degradation for the same number of kWh charged into the battery if you top out at 80% vs 95% (which is what 100% means given the 3.4 kWh buffer).
More simply put, to 1st order accuracy, 4000 cycles of the red line yields a poorer capacity than 4000 cycles in the green line. (To 2nd order accuracy, you have to figure in the degradation. 60% is fewer kWh after 4000 cycles on the red line vs. the green...)

Now, that said, 4000 cycles on the green line is about 500,000 miles of highway driving. On the red line you hit the same battery degradation after 2000 cycles, or about 250k miles. So it all depends on how much reduced range you are OK with at what stage of life of the vehicle. If you dump them after 100k, you won't care. Me, I just have a thing about using things gently if it does not inconvenience me much to leave them better for the next person, even if the next person is a stationary storage system!

 

[ENirogus]

Here's the thing, cars don't last 500k miles, even if the battery is perfect, other things happen to them first.
What will happen to our cars? They will be outmoded by newer technology that is better cheaper and faster before they actually die.

The website you quote is another scientific paper that is not related to actual managed batteries in EVs.

Actual data from actual vehicles shows that Teslas lose <10 percent after 160k miles

https://electrek.co/2018/04/14/tesla-battery-degradation-data/
>>>>>>>>>>
There are a few outlier battery packs out there and they tried to figure out why by gathering other data, like frequency of DC fast-charging and daily state of charge, but there’s no clear indication that any of those factors have any significant impact based on their data.
>>>>>>>>
I am not saying charging to 80 percent doesn't increase battery life, I am saying it is happening at a point where it doesn't matter.
The utility that recycles your battery pack will appreciate the increased capacity.....

 

[David T in Silicon Valley]

The website you quote is another scientific paper that is not related to actual managed batteries in EVs. Actual data from actual vehicles shows that Teslas lose <10 percent after 160k miles

Why are Tesla batteries going to be more relevant than that paper? It is still probably a different chemistry.


As for the real world data, remember how when Hurricane Irma (And Florence and probably other storms) came through , Tesla updated software in evacuation areas so suddenly 60 kWh Model S's had access to a full 75 kWh?

That means "100%" charge on one of those 60 kWh vehicles was actually only 80%. That is huge for battery life.

https://electrek.co/2018/09/12/tesl...pacity-free-supercharging-hurricane-florence/

Yes you might say a car won't last to 500k, but so what? That leaves the battery pack in that much better shape for a stationary storage system. (I still am using a 2014 iPhone btw. I am not so sure I will become impatient with the software in the 15 years it might take me to hit 500k!)

 

[ENirogus]

That means "100%" charge on one of those 60 kWh vehicles was actually only 80%. That is huge for battery life.

Which is exactly my point. Using technical papers has its limitations.

Yes you might say a car won't last to 500k, but so what? That leaves the battery pack in that much better shape for a stationary storage system. (I still am using a 2014 iPhone btw. I am not so sure I will become impatient with the software in the 15 years it might take me to hit 500k!)

Concerning yourself with future uses of your battery pack rather than the usefulness of the vehicle now is impractical. In 15 years a large percentage of all cars will not be on the road, accidents, expensive repairs, corrosion, all take their toll. The cars that will be out there will not have 200k+miles on them, but will be the lightly driven examples. Even if your battery was so abused it had 50 percent capacity, it will have more range than a brand new mini EV. What will new EVs have for range in 15 years? Probably enough that you won't be tempted to keep your Kia going.

My real point is that the right wing bobbleheads will grab onto the whole 'only charge to 80 percent and only discharge to 20 percent' and start calling it the big range lie or some other Tucker Carlsonism.
So again, I will choose to charge per the makers recommendation

 

[David T in Silicon Valley]

Which is exactly my point. Using technical papers has its limitations.

That is why I interpolated between the 100% and 90% degradations in the report. That is a minor limitation for me. 80% fill vs 95% is also a noteworthy difference (to me).

My real point is that the right wing bobbleheads will grab onto the whole 'only charge to 80 percent and only discharge to 20 percent' and start calling it the big range lie or some other Tucker Carlsonism.
So again, I will choose to charge per the makers recommendation

Yah really think they won't find something to exaggerate or present in a misleading way regardless?

Besides, I don't hesitate to take it up all the way when it makes a difference, like on a long road trip. For me it is not significantly less convenient in my day to day usage to run between 20 and 80%...it means maybe I charge 5 times a month instead of 4. For my situation where I can charge at a level 2 at work, it is not even inconvenient. If I had my own level 2 in my garage, it is completely transparent.