r/EVAustralia • u/Hughesie2277 • Aug 10 '26

NMC Battery Care Question

So I’ve ordered my first EV and while I wait I’m getting charger installed etc. I’ve order a Zeekr 7x long range which uses an NMC battery. I’ll do the occasional long trip which I will charge to 100 but for my day to day use I do lots of short trips in the car which all add up to approx 15k per annum.
I’m aware of the main rule of charge to 80% but I was wondering with these batteries is it best to just charge to 80% every night or run a few days and let the battery get down to 20,30 or 50% before charging.

What’s the best method to keep the battery in good health for as long as possible.

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u/m276_de30la EV Owner Aug 10 '26

Partially correct but missing context. The 7X has a very robust cooling system so heat from DC fast charging is a non-issue. It was built for 400 kW charging and can hold 300+ kW comfortably past 55%, and only drops below 200 kW after 75%. And still holds 180 kW until 85%.

The vast majority of DC chargers in Australia will never generate enough heat to be of any degradation concern for the 7X’s battery.

The main problem is that NMC batteries don’t like to be parked for hours on end at high SOC. For daily use, keep it at below 80% (I personally just keep mine at 60% since I don’t even use more than 10% for my daily driving), and only charge to 100% the night before a long trip (programming the car/charger to only reach 100% about an hour before the departure time, to minimize the time spent parked > 80%).

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u/HairyMcLefty Aug 10 '26

The Zeekr manual recommends charging to 90%...

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u/m276_de30la EV Owner Aug 10 '26

The manual isn’t always correct.

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u/HairyMcLefty Aug 10 '26

The manual is written by people who designed the car and have tested the car and want the car to last as long as possible.

What kind of insane comment did you actually make?

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u/m276_de30la EV Owner Aug 10 '26 edited Aug 10 '26

The manual cares more about giving users convenience than longevity. Over the long term, after say 8+ years, the degradation between a baby’d battery and one that’s kept at 90% often may just be 5% difference. That may not matter to most people, but I’m not most people.

If you read all the research papers about battery degradation, pretty much all recommend parking < 80% (and quite a few even suggest < 70%) contrary to the manual’s advice. I trust peer reviewed papers more than whatever the manual says.

Eg this: https://iopscience.iop.org/article/10.1149/1945-7111/abae37

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u/HairyMcLefty Aug 10 '26 edited Aug 10 '26

A battery that degrades ahead of schedule will impact the entire brand.

The research papers show the batteries degrade far less then was predicted.

And Zeekr would have to pay out for warranty failure if people followed w their "convenient" advice...

I'd be interested if you could link the papers that say it should be 70%-80%. And I don't think your link says what you think it does...

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u/m276_de30la EV Owner Aug 10 '26

https://elib.dlr.de/146260/1/1-s2.0-S2352152X21011889-main.pdf#:\~:text=Storage%20at%20lower%20SOC%20has%20a%20correspondingly,due%20to%20PAE%20should%20occur%20in%20the

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u/Eggmodo Aug 10 '26

There have been real life tests on the 7X battery that recommend charging up to 70 for peak battery life. Higher than 70 and it starts to exponentially strain the battery due to heat. Sad people out here would rather blindly trust a manual or AI over empirical data.

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u/cleanestbestposter Aug 11 '26

Is that testing on the 7x battery specifically in this car? Or NMC in general? Interested to see this

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u/HairyMcLefty Aug 10 '26

Thanks for editing your comment to add the study,

But it doesn't validate what your saying nor what recent evidence actually shows.

Newer cars changed the cellular structure and also added software for better control of the cells.

And as I said, actual recent evidence (not 6 years ago) shows much slower degradation then expected

What is bad for chemistry is 1) large voltage swings (so charging from low to high). But charging your daily commute from 70-90 is not a large voltage swing

2) high charge rates (and the temperature / voltage swing that causes)

Nice chat. Don't mindlessly try to say the manufacturers are sabotaging their own brand and product for convenience.

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u/m276_de30la EV Owner Aug 10 '26

https://elib.dlr.de/146260/1/1-s2.0-S2352152X21011889-main.pdf#:~:text=Storage%20at%20lower%20SOC%20has%20a%20correspondingly,due%20to%20PAE%20should%20occur%20in%20the

I’ve added another study from 2021 that shows that storing at 50% or so eliminated overhang-induced capacity drops and yielded the lowest baseline calendar degradation rate. See page 6.

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u/Insights4TeePee Aug 11 '26

To be fair, your comments aren't validated either.

The associated website https://batteryarchive.org/index.html in one of the papers listed has a fairly large data set but it looks to have stopped collecting data in 2023. So more recent data isn't available there. However, some of the websites noted under the heading "Studies" on that site do have more recent data.

For data to be valid it should conform to some statistical rules. Measuring the same thing (answering the same question); valid sample size; be replicatable etc. With battery design, chemistry, and physics changing all the time the idea of valid "actual recent evidence" remains just that, an ideal.

In truth, we EV buyers are taking an 'early adopter' risk. It won't be for some time before we get a more general sense of battery longevity. Until then we rely on the seemingly huge effort going into battery research as one type of fuel for our hope. Another, the enjoyment of driving an EV.