Optimizing battery life.

  • Thread starter Thread starter Dgercp
  • Start date Start date
  • Replies Replies 24
  • Views Views 4K
D

Dgercp

New Member
Is it better for battery health to run charge down to say 30-50% before charging to 80% vs just topping off every night or so to 80% when still having 60-70% battery charge.

I ask because I do low daily mileage and my charger is level 1 so in a 12 hour night can only charge about 15kws. If I run charge down too much I can't get up to 80% after just an overnight charge.
 
It depends what you need, if you need the capacity for your commute or 'just in case' don't worry about it plug it in. You see a lot of wikipedia wisdom here and elsewhere making statements about battery life and using unmanaged battery tests as justification.
I think it is pretty solid that you don't want to run down to below 20 percent 'often' or keep at an indicated 100 percent 'all the time' but honestly you are talking about a few percentage points of capacity many years from now.
I plan on keeping my Kia plugged in in the winter and it will probably stay in the 70s to 80 percent because I have a short commute, so I may switch to my level 1 just so I don't have to think about it. I may have to tell it not to charge[and only warm the battery] if I only go to work and back

It is really about your use, as if you let it run down and have to fast charge that is probably as bad as letting it sit fully charged
 
Since you are charging only LVL1 (slowest possible speed) it is totally ok to charge it to 80% every night.

Actually I do the same and have absolutely no noticable degradation over 2.5 years.
 
Dgercp said:
Is it better for battery health to run charge down to say 30-50% before charging to 80% vs just topping off every night or so to 80% when still having 60-70% battery charge.

I ask because I do low daily mileage and my charger is level 1 so in a 12 hour night can only charge about 15kws. If I run charge down too much I can't get up to 80% after just an overnight charge.
Click to expand...
Why are you charging to 80%? The industry standard for Li-ion battery storage is 40%, you are only using 10-20%, your requirement will be met by a 60% limit, and suit your charging regime. As long as you can access a free QC for any emergency need, your battery will survive best kept about half-charge on average...
 
Ultimately and for long term storage a battery should be held at about half as mentioned, however you need to take into consideration your usage and necessities.

Like you said, if you don't have a good means to charge it quickly enough of you have a longer drive coming up, you won't hurt your battery significantly if you use it as you do.

You shouldn't charge it to 100% every night and never use more than a few, that is definitely not good for it, though.
 
hieronymous said:
Why are you charging to 80%? The industry standard for Li-ion battery storage is 40%, you are only using 10-20%, your requirement will be met by a 60% limit, and suit your charging regime. As long as you can access a free QC for any emergency need, your battery will survive best kept about half-charge on average...
Click to expand...
There is no reason whatsoever for this
Again, this is probably true for unmanaged batteries.
A vehicle is in this day and age a necessity. One needs to plan for contingencies, or we would all be happy with 50 miles of range.
The industry standard for EVs is certainly not 40 percent.

If he charges to 95 percent every night, the battery in his car will last for 1000 cycles with minimal degradation

Worry is the worlds most useless emotion, and a detriment to the expansion of EV vehicles
 
Esprit1st said:
Ultimately and for long term storage a battery should be held at about half as mentioned, however you need to take into consideration your usage and necessities.
Click to expand...
Is this documented somewhere? Thought I had read in more than one place the overall goal is to keep the battery between 20 and 80% as much as reasonably possible.

Also, is it more detrimental to the battery to charge it to 100% using the trickle charger (assuming an owner has the time to do so) versus trying to keep the battery 1/2 charged? I understand a battery theoretically has a limited number of charge-discharge cycles, but I also thought avoiding charging to 100% had to do with the enemy of heat. And I assumed the trickle charger has the advantage of causing relatively little heat, but admittedly I'm just speculating.

Just ordered a Wallbox Level 2 charger, and one of the reasons I chose Wallbox is that it appears to be easy to lower the charge speed. I'm assuming everything else being equal a slower charge speed is better as it creates less heat (when an owner has the luxury of time of a lower charge speed).
 
You are correct. Heat is definitely detrimental to battery health, hence the liquid cooling.

However it is not recommended to have the battery just sit at high level of charge over extended periods of time.

What is "extended"? Good question. I keep everyday charge to 80% and for road trips if needed charge higher to whatever is needed.

Just in general being "nice" to the battery.
 
Dgercp said:
Is it better for battery health ... ?
Click to expand...
Noting the context of the question as posed, the Kona's E63 cell specifications are known and provide data that there is degradation due to cycling the cell and of course age. Using a narrower operating portion of the SoC range is not directly addressed but data from tests on other common Li-po cells clearly shows that life is extended significantly by narrowing the useage to around the middle of the range. Our cells are not magical, they'll respond similarly.
These first graphs show 1400-1600 full-charge-equivalent cycles (at 25°C and down to 80% capacity retention) noting that the defined 0-97% is almost certainly what we see as 0-100% on the dash. Some owners may see higher temps and you can see that at 45°C it's reduced to 800-1000 full-charge equivalents.

upload_2021-8-25_12-17-48.webp

Further graphs in the E63 spec show the effect of "fast charging" by LG's definition which does not significantly reduce life. Read the spec for details. "43kW" seems to be 62 amps (per cell) at 50% SoC, about 1C. 77kW on the entire pack is slightly over 1C.

The next graphs address storage degradation at various SoC levels over 40 weeks. The colours did not come through on the leaked data but I'd suggest that the order of the legends likely matches that of the lines and therefore lower SoCs are advantageous. We don't know what happens after 40 weeks but the lines are unlikely to trend upwards. On first-order levels you could equate your average SoC to these values, e.g. running between 40-60% has a rough equivalency to a storage SoC of 50%.

upload_2021-8-25_12-27-51.webp

This graph from battery university is for common Li-po cells and shows that limiting SoC range to central values is beneficial. Don't forget, 25-75% is half a full cycle, etc.

DST-cycles-web2 2.webp

The important thing in summary is that the cycle life can be multiplied by the range to get the lifetime in terms of driving distance. So even 1,000 cycles could be as much as 450,000 km. However, cycling is happening while driving due to regeneration so that will take a toll as well.
 
Last edited:
data for unmanaged battery cells is not relevant to batteries with cooling systems and battery management systems

IIRC Tesla allows more battery abuse [allows you to have access to more of the percentage of the battery than most] and their batteries are holding up just fine

1000 cycles

more or less 269000 miles in the Hyundai

perspective
 
Even in your colored graph, the likely lifetime of the battery, the range is over 80 percent at half a million miles, and the data from actual cars in the field does not show that kind of degradation
And we cannot charge to 100 percent, or discharge to 0, it won't let us
The difference between 85 percent capacity and 93 percent capacity after a half million miles is in the noise
 
This graph, for instance
https://electrek.co/2020/06/06/tesla-battery-degradation-replacement/#jp-carousel-65299

What does it tell us?
It tells us, that no matter what you do, at 60k miles, you are going to lose 5 percent of battery capacity
No one gets out alive
What else does it tell us?

That almost no matter what you do you will be unlikely to lose more than 10 percent of battery capacity

And
that 10 percent is about all you are likely to see
 
Thank you ENirogus and KiwiME for the stimulating discussion. It has helped with my question. Seems 50% optimal for battery but in real life driving simply keeping battery in 20-80% range most of time will give you adequate battery functionality for may hundreds of thousands of miles. I will stop the worry and enjoy the bliss of EV :)
 
I think people need to stop worrying about it. Waiting to hit turtle mode every time before charging is 'bad'. Charging to 100 percent and leaving it sit there for months is also probably 'bad' Fast charging always and in 120 degree heat is probably 'bad'
They are a consumer product that people need to be able to buy and use, and I think most of them do a pretty good job of making them meet that use.
I worry that EV enthusiasts concerned with battery life after 20 years and a half million miles may scare away the 'normies' who don't want to think about a bunch of rules for charging their vehicle or worry that they will have no range in 18 months because the didn't baby their battery

Even if you charge your battery to 100 percent every single time, from the evidence of EVs in the field, you will see a negligible difference in battery capacity in the time frame your car is likely to be alive.
Assuming from the Tesla data that the lowest depletion numbers were from 'careful' owners and the highest from 'careless' owners, a huge stretch, the difference is maybe about 6 percent at 100k miles.

16 miles of range in a Kona

Meanwhile by only charging to 80 percent you lose 51 miles every single time

Personally I cringe watching those range tests where they try to bring it to zero. Why? Why not note where the car restricts power and call it good?

Personally you won't find me below 20 percent on purpose, maybe if I take a road trip, maybe. If it happens, I will only be sweating because I am unfamiliar with the GOM accuracy down there

I plan on leaving it plugged in in cold weather, so I may have to set charging rules so it is not at 100 percent every day

I mean, you take care of a vehicle, but that is different from worrying about it.
 
Generally you're right. Don't worry, use it!

However, charge to 100% so you don't fall below 20% is easier said than done on road trips. Charging to 100% on road trips is basically impossible. 80% is the max unless you have time to charge over night, which is definitely the way to go. But "on the go" 80% is definitely the max.
 
Esprit1st said:
Generally you're right. Don't worry, use it!

However, charge to 100% so you don't fall below 20% is easier said than done on road trips. Charging to 100% on road trips is basically impossible. 80% is the max unless you have time to charge over night, which is definitely the way to go. But "on the go" 80% is definitely the max.
Click to expand...

Oh for sure. Am I going cross country? Probably not. More likely would be boston to ny or boston to northern NH where you are talking about one partial charge per leg gets you there.
That was the math in buying this car. I looked back over 10 years, and the amount of times that I had traveled anywhere I would even have to charge on the road at all, and I was not trailering something large:
Twice.
In ten years.
I drive all over the place but I don't tend to drive 4 hours at a shot.
 
The other question that I don't think has been answered, particularly about the Kona but could apply to
any other car too, is when, if ever, pack balancing is done. Passive [bleed] top-balancing around 100%
would be easier, even if it's not a lot of waste energy, but if you *never* go there then if that's the
onboard mechanism it may never kick in.

Has *anybody* determined the real story here?

Advice around the e-scooter community suggests fairly frequent charging until the charger stops, to "let
the BMS do its thing". I don't know how much truth there is to that, but it suggests letting all cells settle
to the same OCV in absorption and hope that does the right thing. If they're well-matched, then a bunch
of 20 - 80 in between shouldn't drift too much. But with this sketchy chinese stuff, who knows.

_H*
 
You must log in or register to reply here.
Back
Top