At the end of 2017, Apple admitted that it had been deliberately slowing down iPhones over time to compensate for the inevitable battery efficiency decrease following multiple charge cycles. They then offered highly discounted battery replacements for the next year to apologise for not making this clear sooner.
We are now approaching the end of that year. You now only have a few weeks to take advantage of this offer. We would very much suggest you do take them up on it too - it could extend the lifetime of the phone for years. While Apple have just announced this year's new iPhones, there is really very little here to get excited about. As with all phone upgrades these days, it pretty much just amounts to it being a little bit faster and the camera being a little bit better. Despite the marketing suggesting otherwise, if you already have a half decent phone released in the last 3 years or so, this new version is highly unlikely to improve your life in any perceivable way!
The specifcs
To be eligible for the discounted battery upgrade, you'll need to have any flavour of iPhone 6, 6S, 7 or SE. To begin the process, contact Apple support and let them know you'd like your battery to be replaced. The replacement battery will cost £25 (a £54 discount on the previous price). You have until December 31st to take advantage of this price cut, although we'd advise not waiting until the last minute, as there will no doubt be a massive rush at this point. One caveat here - if your phone is damaged, Apple will not replace the battery without fixing that damage first. This price for this fix could creep up towards the total value of the phone at this point.
Do I need a new battery?
So many of the problems that people have with their phones can be traced back to the battery, even if it doesn't seem that way at first glance. In the case of the iPhone, as Apple have explained, your phone really is getting more sluggish by design. The alternative to this (which is equally, if not more problematic) is to not place a restriction like this on the phone, which can then cause the phone to start behaving oddly and crashing when it starts asking the battery for more juice than it can provide now.
Obviously, the phone manufacturers would love you to get a new phone at this point. In the past, this was usually the sensible thing to do anyway. In the early years of smartphone technology, things will have moved forward a lot since your last phone purchase, so your new phone would be noticably different. However, in the past few years, this isn't really the case any more. It is almost certainly the case that the main improvement that you will be noticing when you get a new phone is down to the new battery. Therefore, if you have a qualifying iPhone, £25 to end up with a phone that will suddenly be as quick as it was the day you bought it again seems like a very good deal!