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.

Replacement laptop batteries cost anything from about £40 to £150. That’s a lot of money, so it makes sense to treat your battery so as to give it the best chance of outlasting the machine. It is very common for the battery to fail after two to three years, but you probably want the machines to last from three to six years.

The best treatment of the battery varies depending upon the type. Somewhere on the battery itself (and you may need to remove it from the machine to find the relevant label), you should find a description as being “Li-ion” (or “lithium ion”) or “NiMH” (or “nickel-metal hydride”.)

NiMH batteries – completely drain the battery every now and again. Do this by using the machine while it is not connected to the power supply until the machine tells you the battery is flat and needs to be re-charged. Do this every month or two. There may be more specific instructions about how often to do this either on the battery itself or on documentation that came with it. If you always use the laptop connected to the mains then the battery will last longer if you completely remove it. If you do this, then put it back in and drain/re-charge it every few months. Incidentally, it can make a laptop much more confortable to use on your lap if the battery isn’t connected as the battery weight is a considerable part of the total weight.

Li-ion batteries – here the advice is NOT to drain the battery completely. On the contrary, keep some charge in it at all times. Again, I would recommend removing it entirely if you are usually connected to mains power, but check it occasionally to make sure it’s got some charge in it and top it up every now and again (see below for checking the charge). The advice with Li-ion batteries is to store them partially charged.

How do you know if the battery is “wearing out”?

It probably won’t charge to 100% and the amount of time you get on each charge reduces. You may eventually get a message popping up telling you to replace the battery.

Remove a nearly dead battery?

It seems sensible to leave a dying battery in the laptop while running the machine off the mains. The theory, of course, is that if the power supply is interrupted then you still have an opportunity to close everything down nicely without problems. Normally I agree, but if you start to get strange things happening to your computer – such as a noticeable time lag between hitting a key and seeing it onscreen – then try removing the failing battery. It seems as if the laptop diverts power to charge a failing battery at the expense of other parts of the system. I may be wrong on why this happens, but it is certainly the case that “keyboard lag” can sometimes be cured by removing a failing battery.

How can I tell how charged the battery is?

Both Macs and PCs have options for displaying an on-screen icon that shows how much charge is in the battery. When the battery is not connected, you can usually get an idea of its state of charge by a series of LED lights on the underside of the battery that are accompanied by a small button (see illustration – yellow highlight). Pressing the button will illuminate the number of LED lights that correspond to the current state of charge.

How do I remove the battery?

Turn the laptop upside down. Batteries come in all sizes and proportions but you are looking for a rectangle that has one or two catches along one side. Typically, one of these catches is not spring-loaded so you can slide it to the open position (usually indicated by an open padlock symbol) and let go. Then push the other catch against the spring and slide or lift the battery out of the case at the same time. See the red highlights in the illustration for spring-loaded and non-sprung catches on a Samsung Q35 battery. Mac batteries are often held in place with a button with a slot across it. Turn the slot by 90 degress and the battery can be removed. Some Mac batteries can’t be removed except by professional repairers as they are entirely contained within the case rather than attached to the underside of it (eg the MacBook Pro).

Extending Battery Life

Given that it would be nice to extend the battery’s life so that it never needs replacing, it may be worth bearing in mind that the more a battery is used, the more of its life is used up, so reducing un-necessary use of the battery may help. Apart from completely removing the battery and running off the mains for most of the time, here are a few suggestions for reducing battery use:

  • Ensure that the laptop at least goes into “sleep” mode if left unattended when running from the battery.
  • All operating systems have options for balancing computer performance against the length of time each battery charge will last. The longer each charge lasts, the longer the battery itself will last.
  • Try to keep the air vents around the casing of the laptop clear of dust, fluff, and nearby obstructions. A good flow of air through the laptop is essential to keep the electronics working within specific temperature limits. If it gets hot then the fan will cut in. The fan needs power and this will come from the battery if the laptop is not connected to the mains. The best way to keep the vents clear of dust is by blowing air into them from an “air duster” (a can of compressed air – available from PC World, Maplins, Rymans etc).
© 2011-2018 David Leonard
Computer Support in London
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