Is it ok to leave laptop charger plugged in

Given how paranoid many of us are about keeping our smartphone batteries going until we can find a charging socket in the nearest coffee shop, train or bus, it’s perhaps understandable that the also-not-insignificant matter of the batteries in our laptops is sometimes overlooked.

We all want our laptop batteries to last for as long as possible, of course. But there are also many unhelpful myths circulating about them, as shown by the popularity of ‘leaving laptop plugged in’ and ‘can you overcharge a laptop’ Google searches by those seeking the truth.

So, what is the truth? As is so often the case with matters like this, the answer’s a bit more complicated than you might initially presume.

No, you can’t overcharge a laptop

Phew! It’s good to get that one out of the way.

You see, although there are two main types of batteries used in laptops – lithium-ion and lithium-polymer – and these are distinctly different technologies, the way they work is actually broadly the same. In both cases, it’s the movement of electrons that creates that much-needed power, with this flow also instrumental in preserving the health of the battery.

The important takeaway point here, though, is that you can’t ‘overcharge’ either type of battery. Even leaving a laptop plugged in once it has reached 100% charge will just mean the charger stops charging the battery.

As a result, the laptop will be left to run directly off the power cable, and once the battery has discharged a bit, the charger will kick back into gear to keep the battery topped off nicely.

So if leaving the laptop fully charged isn’t an issue… what about discharging?

We’re not saying you should absolutely never do this. In fact, it can be a good thing to do once in a while, as it helps your battery to more accurately estimate how much juice it has left, compared to if you left it on 90%-plus charge all of the time. As a matter of fact, leaving your battery on a high charge isn’t great either, as far as longevity is concerned.

The problem is that any laptop battery has a finite number of charge cycles, and the more of these cycles you put it through, the more worn-down it will become. The situation differs from one battery to another, but as a rough guideline, about 500 full charge cycles is typical.

In an ideal world, then, you’d probably keep your battery charged at around 50% – although of course, that’s hardly the easiest or most convenient thing to do.

What other factors should I worry about?

The short answer: heat. Temperatures of more than 30 degrees Celsius have been shown to cause irreparable damage to batteries and shorten their lifespan.

If you store the battery at the same temperature but at a charge of 40%, though, it’ll only lose a quarter of its charge holding capacity over an entire year.

So, there you have it – if you want to keep your battery in optimum condition for longer, the best advice is probably to store it in hospitable temperatures charged at the 50%-ish mark, as tricky as that might be.

So, can I leave my laptop plugged in all of the time?

As we touched on above, your battery will wear down over time, regardless of what you do.

Nonetheless, Battery University’s tests have found that a battery charged to 100% will only have about 300 to 500 discharge cycles, compared to the 1,000 to 2,000 discharge cycles that are possible if you keep it charged between 70% and 80%.

It’s therefore clear that avoiding either of the two obvious extremes – not keeping your laptop fully charged all of the time, but also not completely discharging it – is generally the way to go.

When you combine this approach with a commitment to keeping your laptop battery below 30 degrees Celsius, you stand the best chance of enjoying the maximum lifespan from the battery.