SINGAPORE - All smartphone batteries degrade over time so it is not unusual for Apple to be slowing down the performance of its older phones to help prolong their battery life, according to experts.

But some owners prefer faster performance instead.

They were reacting to Apple's statement on Wednesday (Dec 20) - in response to a claim by an app company at the beginning of this week - that it had introduced a software feature in 2016 to prevent phones from unexpectedly shutting down.

Apple said the move was meant to reduce power demands - which can have the effect of slowing the processor - when a phone's battery is having trouble supplying the peak current that the processor demands.

Currently affected models are iPhone 7, iPhone 6, iPhone 6s and iPhone SE, with other models potentially receiving the same feature in the future.

Ms Karissa Chua, a consumer electronics consultant at Euromonitor International, said it was common for the battery, speed and performance of all smartphones to degenerate over time with every update to the operating system and apps.

She said this was because "with every upgrade to the system, more processing power from the phone's hardware is required and this will place a greater strain on the battery life of the phone".

Professor Subodh Mhaisalkar, executive director of the Energy Research Institute at Nanyang Technological University, said that rather than goading iPhone users to upgrade by making their older phones slower, Apple's move in fact helped consumers by allowing batteries to be used for a longer period.

"(But) it's a trade-off. When your battery is degrading, you have the choice of either living with a slightly slower operation of the phone, or changing the battery," he said.

Prof Subodh added that a typical lithium-ion battery is rated up to a thousand charging cycles, which averages to a battery life of about three years if a phone is charged once a day.

He said: "As one approaches the rated cycles, the battery starts to degrade. All batteries which rely on electrochemistry, not just lithium-ion ones, go through a chemical reaction and, because of this, the material and battery life degrades."

Ms Kiranjeet Kaur, a senior research manager for client devices at market research firm IDC Asia-Pacific, said: "I would think throttling speed to ensure larger gamut of devices get Apple software updates and support is a reasonable trade-off, but transparency would help build user confidence." She was referring to the traditional Apple reticence to share such software information.

Some iPhone users, who said they would prefer a faster phone, also wanted Apple to be more transparent with the effects of its updates.

Civil servant Jovita Chua, 27, said: "If it's a trade-off to fix something then users should know any 'side effects' that are involved from the start. The solution should not be at the expense of the user's experience which might be affected if the phone slows down."

She has used an iPhone 7 for the past four months, and has not updated to the latest operating software as she has heard that battery life might be affected.

Singapore Polytechnic student Kirstin Yip, 19, who has owned three iPhones, including the 6s and 7 models, said: "As a millenial, I'm always on my phone, so fast performance is important to me."

"The phone shutting down by itself and having a shorter battery life are minor inconveniences by comparison."

Mr Chan Choy Kee, 62, who works in aviation management, noticed his three-year-old iPhone 6 Plus slowing down about a year ago.

"It's not right," he said, referring to Apple's throttling of the processor. "Why not just offer to replace the battery instead?"

Replacing an iPhone battery with Apple is free if the handset is still under warranty. If not, it costs $118.