Ask HN: Is charging my phone to 85% saving battery life expectancy? | Hacker News Reader

Ask HN: Is charging my phone to 85% saving battery life expectancy?

16 pointsguilamu12 comments

Since Android 12, I can charge my phone (s10e) up to 85% instead of 100%. Is there any studies on how much this is improving battery life expectancy?

I can also do this on my laptop: up to 60% or 85%. Same question.

Any studies on how much those should impact battery life?

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Someone else can correct me, but from what I've heard, limiting the charge threshold on devices is only helpful if the device is plugged in a majority of the time. A laptop that is primarily docked will benefit from limiting the threshold. Thinkpads (and others) have had this feature for a long time.

With phones, whether it makes a difference, I'm not sure. Smartphones and batteries have become smarter to help with overcharging and extending life of the battery by slowing the charge rate when it gets to over 80% or so. I personally don't use thresholds my phone, it charges fast enough to make up for it.

Someone correct this if wrong but I watched a video that claimed 50% is the optimal level that keeps degradation at lowest levels. That may be why you have the decreasing options on the laptop going even down to 60% which I've never heard of.

It had something to do with the charge of lithium ions wanting equilibrium. The further it is from 50% in either direction causes wear due to ions moving around. Letting the battery completely die also wasn't recommended. We really need some experts to set this all straight!

These days worrying about extending your battery life by 5-10% is not worth the hassle of worrying about it. Apple products seem to have smart enough charging and others are probably similar. Imo not worth wasting brain cycles on.

On a phone when you expect to change it 2 years later - not so much. But that phone easily will last 6-7 years which does matter to some (economically and ecologically).

It’s even worse for laptops where one can keep for 10 years and replacement isn’t as easy as on a phone.

The how much is a difficult question because it depends a lot on the battery design, chemistry, and its integration.

The battery degradation chemical reactions is mostly based on the voltage (state of charge) and the temperature. The higher the voltage and temperature, the more the “bad” chemical reactions will happen.

An always connected laptop is the worst because their BMS (battery management system) are usually shit, the battery is always at a high state of charge, and very warm from the cpu and gpu.

It’s a bit better on a phone.

It’s much better on an electric vehicle with a proper BMS and active cooling/heating.

Keeping your device always plugged in does reduce the overall battery life. When I was on Windows, I used an AHK script that would notify me whenever the laptop is fully charged to unplug the charger.

https://gourav.io/blog/autohotkey-scripts-windows#show-notif...

I read somewhere that charging a phone fully, and then letting the battery die down to zero, then recharging helps keep the battery alive longer than constantly keeping it at 100%. Keeping it permanently charged kills the battery quicker apparently.

It’s been a while since I attended a talk about lithium ion batteries, but there were several issues in the chemistry(which I’m sure have changed in the last 20 years).

One talk covered how you had an expected total number of cycles more than anything else. So you wanted to start between say 85% and draw down to 10% before charging.

Shallow (partial) cycles are better for longevity (measured as permanent capacity loss over time).

The effect is "better than linear;" see Table 2.

https://batteryuniversity.com/article/bu-808-how-to-prolong-...

In general, li-ion has the properties you want: no "memory," deep discharge OK, partial charge OK.

The one it lacks is "shelf life:" they don't like long-term storage at full charge. So they ship at 3.7 volts instead of the "full" 4.2V state. (This is the old wisdom of not keeping your laptop on a charger.)

Lawn tools, for example, might have a smart charger that draws them down after a month without use.

I imagine it's upsetting to need your flashlight, vehicle, etc., and it's only at 50-70% capacity.

If hi speed charging lowers battery life, I follow that low speed charging will lengthen it.

then why would Apple develop a fast speed charger?

So you have to replace the phone more often, netting them more money from you

If it gets proven in the court, then Apple would have to pay for bad PR, refunds and damages

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