Battery life screens on Android smartphones

Smartphone users — casual and enthusiasts alike — are forever in search of longer battery life. While fast charging keeps us topped up every day, the absence of replaceable batteries means eventually the lithium-ion cells enclosed in our phones are going to age and deteriorate, making it harder to maximize battery life.

If you’ve held onto a phone a couple of years, you’ve probably noticed the battery doesn’t seem to last as long as it did when your handset was brand new. Three years down the line and many phones struggle to make it through the day on a single charge. Holding onto a phone even longer can even spell trouble for system stability.

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Unfortunately, battery capacity inevitably declines with age. However, there are things you can do to prolong the life of your battery and smartphone. If you’ve ever wondered what the best way to charge your battery is, here are some scientifically proven tips to maximize battery life.

Partial charging is a healthy habit

One particularly persistent battery myth is that you need to occasionally fully discharge and recharge to erase “battery memory.” This couldn’t be more wrong for lithium-ion batteries. It’s a leftover myth from lead-acid cells and it’s actually quite undesirable to charge your modern smartphone in this way.

See also: Best battery saver apps for Android

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% charge before the current begins to fall until the capacity is full.

Partial charging is just fine for lithium-ion batteries and even has some positive benefits.

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% range keeps the voltage lower and might slightly prolong the battery’s lifespan.

Lower battery voltages help prolong capacity over time. Green: lower voltage charging for first ~65%. Yellow: Start of constant voltage. Red: Long period of high voltage charging for last 15%.
Furthermore, the “depth-of-discharge” has a similar effect on the total discharge cycles before battery capacity drops off. This refers to the amount the battery used up in between charges. Smaller discharges, in the region of 60% rather than 100% between refueling can double the lifespan of your battery, and only using 20% can double the life again.

Smaller but regular top-ups are much better for Li-ion batteries than long full charge cycles.

Using up just 20% of your battery between charges isn’t practical, but topping up when you’ve used about half will see an improvement in your battery life over the long term. Especially if you avoid charging up to full each time too. The bottom line is that smaller, regular top-ups are better for Li-ion batteries than long full charge cycles.

Avoid idle charging

Yootech F500 Wireless Charger with iphone and accroutements
Eric Zeman / Android Authority

Charging overnight or in a cradle during the day is a very common habit, but it’s not recommended for several reasons (the old “overcharging” myth isn’t one of them). First, continuous trickle charging of a full battery can cause plating of the metallic lithium, which reduces stability in the long term and can, in rare cases, lead to system-wide malfunctions and reboots. Secondly, it leaves the battery at a higher stress voltage when at 100%, as we just mentioned above. Third, and most important, it creates excess heat caused by wasted power dissipation.

Some phones disable or slow down charging when nearing full capacity. Use these options.

Ideally, a device should stop charging when it reaches 100% battery capacity, only turning the charging circuit back on to top up the battery every now and again — or at the very least reducing the charging current to very small amounts.

While some phones disable charging once full, many continue to pull up to half an amp and sometimes more from the wall outlet. Turning the smartphones off doesn’t make a difference in many cases either. While this isn’t a huge amount of power, it’s going to stop your phone from cooling down as quickly and will continue to cycle through a small part of the battery, resulting in a mini-cycle.

A final point worth mentioning is parasitic load. This occurs when the battery is being drained significantly at the same time as being charged, such as watching a video or gaming while charging.

Parasitic loads are bad for batteries because they distort the charging cycle and can induce mini-cycles – where part of the battery continually cycles and deteriorates at a faster rate than the rest of the cell. Worse still, parasitic loads occurring when a device is fully charged also induce higher voltage stress and heat on the battery.

Gaming or watching videos while charging is bad because it distort charging cycles.

The best way to avoid parasitic loads it to turn your device off while charging. But that’s not really realistic. Instead, it’s best to keep the workload light while the device is plugged in, leaving it idle most of the time. Browsing the web is probably fine. Also, remember to unplug it once the battery is topped up enough.

Heat is the enemy of long battery life

Asus ROG Phone 5 product shot of the battery and charging logos up close
Ryan-Thomas Shaw / Android Authority

Along with all of the above, temperature is an equally key contributor to longevity and helping to maximize battery life. In fact, it’s arguably the biggest killer of long-term battery health. Just like high voltages, high temperatures stress the battery and make it lose capacity far more quickly than when kept at lower temperatures.

A cell kept between 25 – 40 degrees Celsius (77 – 86 degrees Fahrenheit) should retain around 85% to 96% of its capacity after the first year with sensible charging cycles. Raising the temperature regularly above 40°C (104°F) and charging to 100% sees this fall to just 65% capacity after the first year, and a 60°C (140°F) battery temperature will hit this marker in as little as three months.

The ideal temperature to maximise battery cycle life is below 40°C

A battery dwelling in a full state-of-charge exposed to a high temperature is the worst of all worlds and the number one thing to avoid when charging your phone. So no leaving your phone under your pillow to charge at night or plugged in on the dashboard of your car on a hot day.

Read more: Quick Charge 5 tested – Smarter charging for longer battery life

Fast charging technologies are a contentious issue here, as the higher current and voltages lead to a hotter device. With capabilities exceeding 60W and pushing to 100W even in smartphones, this is quickly becoming an issue for device longevity. Fast charging is fine for a small top-up, but numerous standards we’ve tested regularly exceed 40°C when charging for more than a few minutes. As you can see in the graph below.

Leaving your phone to fast charge up for 5 to 15 minutes won’t lead to major overheating problems, but I certainly don’t recommend using them for a full charge. Instead, you’d be better off using a temperature-aware fast charging solution or switching to a slower charger, especially if you plan to plug your phone in overnight.

How to maximize battery life long-term

Lithium-ion battery technology is well understood these days and smartphones are built around our use cases, but bad habits and myths still permeate the 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 battery life and thus our smartphone’s 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.

Up next: The best portable chargers and power banks

Here’s a TL;DR summary of the battery tips above:

What’s the best way to charge your smartphone?

  • Avoid full cycle (0-100%) and overnight charging. Instead, top up your phone more regularly with partial charges.
  • Ending a charge at 80-90% is better for the battery than topping all the way up to completely full.
  • Use fast charging technologies sparingly and when your device is cool.
  • Heat is the battery killer. Don’t cover your phone when charging and keep it out of hot places.
  • Don’t play intensive games, stream videos, or run other intensive workloads while charging to avoid heat and mini-cycles.