Why is it that your phone's battery seems to get worse over time? At first it might have power to spare as you snuggle into bed at the end of the night, but as time goes on you find your battery is just half-full by lunchtime.

Partly it's because your use of the phone - the apps you install, the junk you collect, the customisations you make, and the more and more notifications you receive - puts more strain on the battery. (Read our tips on how to extend battery life.)

But the other thing to consider is that phone batteries do degrade over time, which means they are increasingly incapable of holding the same amount of power. While they should have a lifespan of between three- and five years, or between 500- and 1000 charging cycles, a five-year-old phone battery is never going to keep going as long as a brand-new battery.

However, armed with our tips for best battery care practice, you can maintain your smartphone battery health much longer.

When should I charge my phone?

The golden rule is to keep your battery topped up somewhere between 50- and 90% most of the time. So top it up when it drops below 50%, but unplug it before it hits 100%. For this reason you might want to reconsider leaving it plugged in overnight.

Giving your phone a full recharge is not fatal for a phone battery, and it seems almost counter-intuitive not to do so, but giving it a full recharge every time you charge it will shorten its lifespan.

Likewise, at the other end of the scale, avoid allowing your phone battery to get below 20%.

Should I charge my phone battery to 100%?

No, or at least not every time you charge it. Experts recommend that you do a full zero to 100 percent battery recharge (a "charge cycle") once a month. This recalibrates the battery, which is a bit like restarting your computer.

Also see: Best power banks

Should I charge my phone overnight?

As a rule, it's best to avoid, despite the convenience of waking up with a full battery in the morning. Each full charge counts as a 'cycle', and your phone is only built to last for a set number. 

While most modern smartphones have built-in sensors to shut off charging when they hit 100%, if still turned on they will lose a small amount of battery while idle before

Your best policy is to have Do Not Disturb and Airplane Mode switched on. Better still, you could completely switch off your phone, but that may not be possible if you rely on it as an alarm. 

Some devices are also set to power up once the cable is connected by default. Even during waking hours, it's best to catch your phone before it hits 100%, or at least not leave the charger supplying charge to an already full battery for too long. 

If you are leaving it plugged in for a long period of time, removing the case can prevent it over-heating.

Will fast-charging damage my phone?

The majority of modern smartphones support some form of fast-charging, however this often requires you to purchase an additional accessory. The industry standard is Qualcomm's Quick Charge, which delivers 18W of power.

However, many phone makers have their own fast charge standard, many of which can deliver even faster speeds by adjusting power management code to request a higher voltage charge is sent. Samsung is now even selling a 45W charger!

While fast-charging itself will not harm your phone's battery, which is built to support it, the heat generated will potentially affect its lifespan. So it's on you to balance the advantages of faster charging with the convenience of quickly topping up your phone before you dash out the door.

In the same way that phone batteries don't like extreme heat, they also don't like the cold. So it goes without saying that you should avoid leaving your phone in a hot car, on the beach, next to the oven, out in the snow. Typically, batteries perform at their optimum somewhere between 20 and 30°C, but short periods outside of this should be fine. 

Can I use any phone charger?

Where possible use the charger that came with your phone, as it is sure to have the correct rating. Or make sure that a third-party charger is approved by your phone's manufacturer. Cheap alternatives from Amazon or eBay may harm your phone, and there have been several reported cases of cheap chargers actually catching on fire.

That said, your phone should draw only the power that it needs from a USB charger.

Also see: Best USB chargers for your phone

Battery memory effect: Fact or fiction?

The battery memory effect concerns batteries that are regularly charged between 20- and 80% and suggests that the phone might somehow 'forget' that extra 40% you routinely ignore.

Lithium batteries, that are in the majority of modern smartphones, do not suffer the battery memory effect, though older nickel-based (NiMH and NiCd) batteries do.

Storing battery tips

Don’t leave a lithium battery lying around too long at 0% - if you're not using it for a while, leave it with around 50% charge.

You'll find the battery will drain between 5- and 10% each month, and if you let it discharge completely it might become incapable of holding a charge at all. That's probably why an old phone's battery life is so much worse after a few months in a drawer, even when it hasn't been used.