Laptop and Mobile Batteries

How should you treat your battery to give it a long life?

Battery IndicatorLeave laptops plugged in permanently?
Drain batteries completely?
Remove batteries that are not being used?

A battery’s “lifespan” is the length of time it lasts until it needs replacing (cue parrot sketch), whereas its “life” is the length of time it can function between charges. From time to time one of my IT Support clients will ask me how to treat a battery so that it will last as long as possible in both these respects.

And here is where the fun starts as the advice for modern (lithium ion – or li-ion) batteries is the opposite of what used to be the case when devices were powered by nickel cadmium (nicad) batteries. With Nicad batteries, if you never let them drain right down, or if you never recharged them to the maximum, then the battery could experience something known as the “memory effect”. It was as if the battery “forgot” that it was possible to charge past, say, 80% of its capacity and so it never did so. This gave rise to the advice that you should regularly completely discharge and recharge your battery (be it on a laptop or mobile phone).

All mobile devices these days use lithium ion batteries – whose lifespan is actually reduced by completely charging and discharging them too often as these batteries can only be completely charged and discharged a finite number of times (usually quoted as being somewhere in the range 500-1500 times). Indeed, the advice for li-ion batteries is to aim to keep them charged between 20% and 80% all of the time. Exactly the opposite of nicad batteries.

Dead ParrotIn the past, I used to have Samsung laptops that had their own utility that allowed you to limit the charge on the battery to 80%. Disconcerting if you didn’t know why your battery never charged to the full capacity, but a useful utility if you did. Since I’ve never come across such a utility on other makes of laptop (or mobile phone), I would guess that it’s not absolutely critical. Now that I use a Dell laptop (that doesn’t have such a utility) I certainly can’t be bothered plugging/unplugging the mains lead just to keep the battery charged at 80% or less. The fact that most laptop batteries are non-removable these days also suggests to me that it’s not exactly critical if the power lead is left in, recharging the battery, all the time.

If you don’t intend to use a device for an extended period of time (months, say), then the advice with li-ion batteries is to charge them to about 50% before putting the device and/or battery away.

Even with li-ion batteries, it can be useful to completely drain and recharge your battery every now and again if you see that its life seems to be shortening – ie it doesn’t go as long before needing a recharge as it used to. My iPhone 6S battery level indicator went potty last weekend – dropping very rapidly without any obvious reason. So, I decided to run it completely flat and to recharge it as I know that that can help (it’s known as “calibrating” the battery). I got it all the way down to 1% very quickly but then it stubbornly refused to go completely flat for another couple of hours. And then the penny dropped. I had “upgraded” (ha-ha) to IOS v 11.3 that morning. A quick google confirmed that other people were having the same issue after the upgrade. The consensus seems to be that everything will probably settle down after a few days and the battery has properly calibrated. Failing that, we can expect an early upgrade to the upgrade.

IOS v11.3 Battery Health
The Battery Health option shows that my iPhone’s battery can charge to 89% of its original capacity. It should be OK until it drops to 80%.
I suspect that all this happened because Apple’s IOS v11.3 has a new option (under Settings, Battery, Battery Health (beta)) to see how good your battery is. This is in response to Apple having to admit recently that they do slow down older iphones to stop them from cutting out when the battery can’t cope with the demands put upon it. As long as the battery is still capable of being charged to at least 80% of its original capacity then the phone’s performance will not be affected. It’s probably something to do with this new development in the operating system that’s caused the battery level indicator to go haywire.

Of course, if I’m wrong about all this and the battery is knackered (despite, apparently, still being capable of 89% charge), then I now know where to take it – see this blog on “Is it worth mending an iPhone?“.

… all sorted. After a couple of days the battery meter is now behaving itself properly again.