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.

But it's partially our fault because we've been charging them wrong this whole time.

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.

Many of us have an ingrained notion that charging our smartphones in small bursts will cause long-term damage to their batteries and that it's better to charge them when they're close to dead. But we couldn't be more wrong.

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

Don't keep it plugged in when it's fully charged

According to Battery University, leaving your phone plugged in when it's fully charged, like you might overnight, is bad for the battery in the long run.

Once your smartphone has reached 100 percent charge, it gets 'trickle charges' to keep it at 100 percent while plugged in. It keeps the battery in a high-stress, high-tension state, which wears down the chemistry within.

Battery University goes into a bunch of scientific detail explaining why, but it also sums it up nicely: "When fully charged, remove the battery" from its charging device. "This is like relaxing the muscles after strenuous exercise." You too would be pretty miserable if you worked out nonstop for hours and hours.

Will fast-charging damage my phone?

Most new smartphones support fast-charging, yet often come with a lower-specced charger in the box. The most common fast-charging standard is Qualcomm's Quick Charge, but phone makers often have their own alternative to this (which is often faster still).

These phones have special code usually located in a chip known as the Power Management IC (PMIC) that communicates with the charger you are using and requests that it send power at a higher voltage.

While fast-charging itself will not harm your phone's battery, which is built to support it, the heat generated from that charging likely will affect its lifespan. So a quick top-up with a fast charger is unlikely to hurt your phone, but prolonged and regular fast-charging might mean the battery doesn't last quite as long as it would were you to use a slower charger. 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 or, erm, in the freezer.

Partial charging is the way to go

Partial charging is just fine for lithium-ion batteries and can actually have some positive benefits for cell longevity. To understand why it’s important to appreciate how a battery charges. When closer to empty, Li-ion batteries draw constant current and operate at a lower voltage. This voltage gradually increases as the cell charges up, leveling off at around a 70 percent charge before the current begins to fall until the capacity is full.

Importantly, operating at a low voltage is good for a battery’s lifespan, increasing the number of available charging cycles before you’ll start to see a major reduction in capacity. Roughly speaking, every 0.1V decrease in cell voltage doubles the cycle life, according to Battery University. Therefore, charging up your phone in that 30 to 80 percent range keeps the voltage lower and prolongs the battery lifespan.

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 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.

Keep it cool

Smartphone batteries are so sensitive to heat that manufacturers suggest you remove certain cases that insulate heat from your phone when you charge it. "If you notice that your device gets hot when you charge it, take it out of its case first." If you're out in the hot sun, keep your phone covered. It'll protect your battery's health.

Bringing this all together

Lithium-ion battery technology is well understood these days, but bad habits and myths still permeate public consciousness. While most of these habits won’t severely negatively impact your phone’s battery life in the medium term, the decline in removable phone batteries means we should take extra precautions to maximize our phone’s battery life and cell longevity.

Broadly speaking, smaller regular charge cycles and keeping your phone cool are the key things to remember. Although I should point out that different phone batteries will always age slightly differently depending on how we treat them. Here’s a TL;DR summary of the battery tips above:

What’s the best way to charge your smartphone?

• Avoid full cycle (zero-100 percent) and overnight charging. Instead, top-up your phone more regularly with partial charges.
• Ending a charge at 80 percent is better for the battery than topping all the way up to 100 percent.
• Use fast charging technologies sparingly and never overnight.
• Heat is the battery killer. Don’t cover your phone when charging and keep it out of hot places.
• Turn your phone off when charging, or at least don’t play games or watch videos to avoid mini-cycles.