SINGAPORE - The Straits Times looks at the science behind charging and maintaining the lithium-ion batteries in mobile devices.

How might a battery be damaged by charging?

The lithium-ion batteries in mobile phones can deteriorate quicker if they are fast-charged when the power is running low.

Dr Chiam Sing Yang, deputy executive director of the Agency for Science, Technology and Research’s Institute of Materials Research and Engineering, said the sudden influx of electrical current will mean that some lithium ions are left unused within the battery while those nearer to the surface of the battery container are charged up.

Over time, this can cause the ions to lose their charge, deteriorating the battery’s performance.

“It’s like trying to fill seats in a cinema,” said Dr Chiam. “If everyone rushes in suddenly, the seats won’t be filled up optimally.”

Batteries can also be damaged when they are charged for a long time as they hold higher voltage when filled to the brim, exerting stress on the battery, he said.

“The latest products today generally have battery management software, but, if there is a choice, it’s still better to avoid charging overnight,” added Dr Chiam.

How long would a mobile phone battery typically last?

Modern mobile phone batteries should be able to be charged at least 500 times before they fade and fall below 80 per cent of their original capacity, said Associate Professor Xu Yan from the Nanyang Technological University’s School of Electrical and Electronic Engineering.

This will depend on the brand and quality of the batteries, and whether software is used to help boost the battery’s performance, he added.

According to Apple, a typical iPhone battery is designed to retain up to 80 per cent of its original capacity after 500 complete charge cycles.

A charge cycle is when a battery is fully charged and depleted.

Oppo said that its phones can keep 80 per cent of its capacity after 1,600 charge cycles.

Users can check the overall battery capacity of their device in the settings menu of their iPhone and Android devices, including Samsung and Oppo phones.

Will my phone be damaged if it is fully drained?

Fully draining a device’s battery regularly can shorten its lifespan, as doing so degrades the electrode layers and other components within the battery.

This causes the lithium ions to lose charge, and the battery will not be able to hold as much power, said Prof Xu.

Keep the battery between 50 per cent and 80 per cent charged so that there will be less stress exerted on the battery’s components as the voltage is kept lower, he said.

“The deeper discharge a battery undergoes, the more stress will be exerted inside,” added Prof Xu.

Phones should also be half-charged when they are kept in storage for extended periods.

Is it safe to mix and match charging bricks?

Flagship phones these days often do not come with a charger, which sees buyers turning to third-party brands for cheaper and faster-charging power bricks.

But users should first ensure that their device can withstand the current that is being delivered by the charger.

Otherwise, it can cause overheating and damage the phone’s battery, said Dr Chiam.

Newer flagship devices often come with battery management systems that regulate charging levels, making it safe even when higher wattages are involved, he said.

But high-watt chargers can be dangerous for devices without battery management software, as high currents exert stress on the battery, said Dr Chiam.

Users can check the phone’s optimal charging speeds on the device’s specification sheet, ensuring that the wattage delivered by the charging brick does not surpass the phone’s limit.