Phone battery maintenance

[John B]

What are the best habits for charging your phone in this day and age? My last phone went through 3 batteries: the first one ended up swelling due to it being left on the charger a lot at 100%, the second was genuine battery but didn't last more than 12-18 months, by the 3rd battery I learned my lesson. I used a non genuine battery which had obviously less capacity, but I took it off the charger once it reached full charge. It has lasted til present day without swelling up.

Unlike the old phone, my new one, a Pixel 8, has a glued in battery in a sealed case like most new phones. So I would like to maximise its lifespan. So far I have only needed to slow charge the device up to 80%, which is plenty of capacity to get me through more than 24 hours. These seem like pretty basic conventional tips to maintain a battery.

However I read an article which proposes doing what I used to do: https://akc3n.page/posts/battery-management/

ie leaving the device fully charged and connected to power. In fact it proposes my current habits are detrimental to the battery.

While many of the points seem like they should be correct, ie a modern BMS should be able to manage charging and maintaining of a battery to maximise lifespan, my prior experience tells me otherwise. Also, I would tend to believe manufacturers prioritise battery capacity and charging speed at the expense of longevity. They have an incentive to perform well in immediate reviews and spec comparisons, but have little concern whether the battery goes bad after a couple of years and out of warranty.

The article also alludes to something I have wondered, whether the phone is able to operate purely on external power when it's connected, and avoid cycling on the battery to preserve it's life. Again that seems like it would make sense, if it doesn't result in the battery swelling due to a high state of charge.

[nctnico]

You can buy devices which limit how quick and to what level your phone charges the battery.

The article doesn't touch the subject of super fast charging. There seems to be a race going on between manufacturers to make a phone charge as quick as possible. Some even claim 10 minutes. Needless to say this has to be bad for the battery. More sensible manufacturers leave some control to the user. Apple for instance, allows to set the charging speed depending on your habits so the battery life is extended as much as possible.

[Halcyon]

What are the best habits for charging your phone in this day and age?

If you're using your phone everyday, keeping it plugged in on the charger overnight won't damage it. Devices like phones don't overcharge lithium cells and some of the more mainstream phones like the Google Pixel, Apple iPhone and Samsung Galaxy phones will adjust their charging behaviour based on your habits (e.g.: If it knows you're not going to be using your phone for the next 8 hours, it'll charge slowly to prolong the life of the battery).

Generally speaking, slower charging is better, avoid complete discharges where possible, and avoid excessive temperatures.

A good quality phone/battery should easily last you several years, even with almost daily recharging. Even if you keep the phone plugged in almost 100% of the time, the battery pack shouldn't swell under normal conditions.

[Andy Chee]

My iPhone 7 "learns" the power consumption patterns, battery ageing patterns, and charging patterns.  So if my ancient phone has this capability, I'm sure newer phones have it too!

[Bud]

I have had an iPhone 5 for 10 years, went trhough 1 replacement battery which is still running, though the phone now is only used as a weather gadget and alarm clock. I used only genuine apple chargers each night going to bed and unplugged in the morning. The original battery lasted 5 years with this charging schedule. And I set battery discharge alarm to 15% and critical alarm to 10%.
I think the guy has little idea about what he wrote. Look at what happens to laptop batteries when you mostly use external power. Even if you do not use the battery but leave it in the laptop powered externally, it dies in 2 years.

[nctnico]

Look at what happens to laptop batteries when you mostly use external power. Even if you do not use the battery but leave it in the laptop powered externally, it dies in 2 years.

That depens entirely on the design (as usual). I have a decade old laptop which I always use with external power. The battery is still good.

[NiHaoMike]

You can buy devices which limit how quick and to what level your phone charges the battery.

Or just use this free app if your device is supported.
https://f-droid.org/en/packages/mattecarra.accapp/

[nctnico]

You can buy devices which limit how quick and to what level your phone charges the battery.

Or just use this free app if your device is supported.
https://f-droid.org/en/packages/mattecarra.accapp/

But it requires rooting your phone which is not a good idea. And it may cause you other limitations. Online banking apps are likely not to work on rooted phones as banking apps actively check if your phone is rooted and won't start if a rooted device is detected.

[John B]

On the topic of laptop batteries, my 2012 Macbook Pro's battery died in a similar way to my phone. I always kept it plugged in, and eventually the battery swelled.

I've switched to GrapheneOS, and have set things up in what I consider the "proper" way, ie maintaining a locked bootloader, principles of least privileges yada yada. Native solutions to battery management don't seem to exist, but I don't want to root the phone. Maybe a simpler approach would work:

For phone charging, I tried charging the phone with my bench PSU in CC mode. I assume the phone has it's own voltage vs current map in the BMS and charging firmware, it was steady at around ~4.7V @ 125mA. It probably calculates the voltage drop at connection vs charging.

I wonder if an USB inline buck converter with a soft current limiting circuit to set an adjustable current limit would be a safe approach? Plugged into a USB 2.0 port, the current is limited to 500mA anyways. Dropping the current limit to around 100-200mA would be a good overnight charging rate.

Thinking rationally, by the time I've made it, I'm halfway in cost to the price of a new battery. An inline resistor on a cheap USB cable would probably have a similar effect. Still, it might be a handy gadget to make.

[nctnico]

As noted before: such gadgets already exist 

[John B]

As noted before: such gadgets already exist 

Do you have a link to a particular device?

I'm still tempted to make my own. All I'd need is a simple buck converter like the TPS54231D (3.5V min input voltage, high side MOSFET for low dropout) and everything else I have on the shelves.

[nctnico]

These are the two I know about:
https://chargie.org/
https://www.liionpower.nl/

[John B]

I did some experimentation with simple resistances in series with the 5V line (no data lines connected), and it seems that the phone goes into discrete charging modes/levels. Ie 100mA, 300mA and then 500mA, rather than a variable input current based on input voltage drop.

It seemed to work when I tried charging the phone on the bench PSU in CC mode, but I didn't scope the line to see if there were 2 control loops fighting against one another. I'm out of my depth with the USB standard to know if CC charging is a safe way to do so.

So in conclusion, the $1 donor cable and 1c resistor is currently the winner in battery charging management.

[IanB]

What are the best habits for charging your phone in this day and age?

Hard to say, since it would take many experiments to produce hard data vs. anecdotal evidence.

That said, I use the slowest charger available, and charge as infrequently as possible (only charging when the low battery warning appears below 20%). This minimizes the number of charge cycles, and it minimizes the heating of the battery during charging. When I do charge, I let it reach 100% most of the time.

After 33 months, my battery health monitor is reporting 98% of nominal capacity (which is sad, I was hoping it would still be 100%). I guess batteries don't last forever.

[SiliconWizard]

"Normal" mobile phone usage makes it rather unlikely to have its battery on an almost full charge for most of its operating time (while this is not uncommon for laptops). Keeping Li-on batteries on full charge for extended periods of time does reduce their lifetime. The actual SOC above which it's detrimental really isn't a fixed value, all depends on the battery itself and other factors. You can find studies with anything from maybe 60% to 80%.
And yes, high charging currents (which allow "fast" charging) are also detrimental. So your best bet overall is usually to charge your phone without the fastest charging mode and not leave it on charger all the time as soon as you're staying somewhere with it. Leaving it on charger will not destroy it nor "overcharge" it at all, it's just that the longest it remains over say 80% overall and the shorter its lifetime will be. A few hours per day is not too bad (so, "overnight"), but if you put it on charge, as I mentioned, most of the time and only leave it on battery alone for just a couple hours a days when you're not near a mains plug, that's clearly not ideal.

Don't expect your phone battery to last (by that I mean: capacity still above 50% of nominal) for more than about 3-4 years even with a lot of "care" anyway. Those batteries are rated for a few hundreds cycles and that's it. The average is around 500 cycles for 80% residual capacity (which is less than 2 years if you do a full charge every day, which is not uncommon for recent phones and medium users). Beyond that, it depends a lot on the battery, but it will degrade at a faster rate.

[John B]

Yep, I won't overthink the situation.

However.....

I will make the observation that 90-100mA charging current on my phone is only slightly above idle power consumption, resulting in a charge rate of 1% per hour. Hypothetically this would be the best situation when the phone is at home since the power for the phone should be sourced from the external power rather than cycling the battery?

Asking for an OCD friend.