A report showed that out of eight mobile phone models tested, LG's G Flex performed best with its 3,500mAh (miliamp hour) battery, suffering only a 3% drop in performance over a two-year span — which was created in a laboratory setting.

The battery originally held a charge for eight hours, 40 minutes, which fell to eight hours and 23 minutes after two years' worth of use.

The Samsung Galaxy S5 — LG's competitor on its home turf — with its 2,800mAh battery, lost 12% of its charge, from nine hours, 31 minutes new down to eight hours, 22 minutes.

Apple's iPhone 5S and its 1,560mAh battery lost 13% of its charge, from five hours, 50 minutes down to five hours, three minutes.

The consumer watchdog on Tuesday revealed the result of the seven-month experiment it conducted in collaboration with the International Consumer Research and Testing consortium.

The experiment tested eight phones and six tablets of various brands for battery endurance.

The testing team simulated 24 months of use by charging the phone 365 times, assuming that users charge their phone once every two days.

They attempted to replicate real-life scenarios by streaming online video on the device with Wi-Fi on full brightness, charged it when the power dropped to 20%, and kept repeating the process.

The team then measured the time it took for the battery to drop from 100% to none, as they applied various operating conditions with the same brightness to every prepared sample.

Professor Michael Hui King-man, chairman of the council's publicity and community relations committee, said the result was satisfactory, adding that the life of a mobile phone also depended on various other factors, such as the size of the device's screen and its processing power.

He noted that some devices did not come with a warranty as long as the phones tested.

For example, LG provided only a six-month warranty for the batteries of its two phones tested. The battery for Nokia's Lumia 1020, which came last in the test, also had a six-month repair warranty, as did the Samsung S5.

The warranty for mobile phones usually covers one year.

Since most phones have built-in batteries, Hui said, the limited warranty period and often hefty costs to fix a battery problem could cause an otherwise perfectly functioning phone to be discarded, which would damage the environment. He said consumers could be put off when they were asked to pay a fee of HK$269 to HK$1,600 to repair or replace their phone's battery. Some companies also charged an inspection fee of $100, he added.

Hui said an alternative option for consumers who have problems after their warranty has expired might be to use a reliable phone repair shop.

While the protection of personal data might be a concern, he suggested users should remove memory cards from the devices before taking it to a shop.

Gilly Wong Fung-han, the council's chief executive, said: "The battery ties with your phone. If the battery dies, your phone dies."