Next Tuesday (14 September), Apple will almost certainly unveil this year's iPhone models, and new rumours about what's in store are surfacing right up to the last minute.

One that's just popped up is particularly appealing. If we can believe a number of Twitter posts by the technology leaker Max Weinbach, as quoted by MacRumors, the new iPhones will offer significantly longer battery life than the equivalent 12-series models.

For the iPhone 13 mini (as compared to the iPhone 12 mini) the increase should be about an hour, which will be more than welcome. For the Pro models the improvement will be smaller, because the new 120Hz ProMotion screen consumes a lot of energy.

(The ProMotion display is one of the key upgrades this year, having disappointed many by its complete absence from the new iPhones in 2020. But the 13 Pro and 13 Pro Max are expected to be the only handsets to get lucky this time round, with the cheaper models missing out on 120Hz again.)

The improvement in battery performance, according to Weinbach, is down to an increase in capacities. The 13 Pro Max, for example, will have an 18-20% larger battery than the 12 Pro Max.

Weinbach also claims that the Apple Watch Series 7 and the third-gen AirPods - both rumoured to launch at the same event as the iPhone 13 - will also offer longer battery life than their predecessors.

Apple fans ask for improved battery life pretty much every year, but one wonders if they would actually vote with their wallets if an iPhone came out that compromised on features and portability in order to ramp up battery performance. Features sell; slimness sells; would a bulky, low-powered iPhone that lasts for three days make sense commercially? That's debatable - but as ever it's good to hear that Apple is working to make some improvements in this important area.

Last year's iPhone 12 and 12 Pro both had lower-capacity batteries than their predecessors, yet in our tests they managed to outlast the iPhone 11 and 11 Pro respectively. This seemingly unexpected result is likely to be the result of the software improvements Apple makes each year to optimise the way its hardware runs. Combine this process with upgraded hardware and the results could be very pleasing indeed.

You can find out if these reports are true and what else Apple has come up with next Tuesday: the event starts at 10am PDT on 14 September, which translates to 6pm UK time. Here's how to watch the iPhone event live. For all the latest leaks and rumours, check out our regularly updated iPhone 13 news hub.

This article originally appeared on Macworld Sweden. Translation and additional reporting by David Price.