It took a year for the love affair between fans and the Apple iPhone to sour. The original iPhone was greeted with round-the-block queues and near-universal praise. But its 3G successor has not fared quite so well. Within a fortnight of going on sale, complaints started to appear online from users who found the handset could not make it through the day without a recharge. The 2G iPhone was designed to last for eight hours of normal use; on anecdotal evidence, the 3G version gets about five hours.

On top of that, people in the US and in some other countries found that their handsets kept dropping calls. Blogger Darlene McNeill claimed she went from a Nokia Series 60 phone to the 3G iPhone and back in less than two weeks because the battery life "just couldn't cut it".

Yet, in its tests with consumers, Strategy Analytics found the iPhone's battery held up well, although 3G phones generally do not last as long on one charge as 2G handsets. Standby time on the phone is average for a 3G handset; talk time is generally better. "As a phone, it's in the right ball park," says Neil Mawston, associate director at Strategy Analytics.

The iPhone's power problem revolves around its big selling point: how it handles data and internet access. Apple built a device that makes people want to use those services, but they suck the life out of the battery. Apple was perhaps not prepared for the users who love the iPhone too much. "Because it is such a feature-rich device, people are using more of the functions than they would on a smartphone-type device," reckons Doug McEuen, senior analyst at ABI Research.

"Traditional [mobile] phones have been designed to cope just with voice and SMS. The iPhone came along with lots of data-intensive applications and features and they, naturally, consume more battery power," Mawston says.

Running on empty

Manufacturers do not yet understand how data usage affects battery life. "It is going to be trial-and-error at this stage," says McEuen. Some weaknesses could just be own goals. Gartner analyst Ken Delaney found a weak spot in how the iPhone deals with email pushed from servers running Microsoft Exchange.

"We seldom experienced a full day of use," Delaney wrote in a report on iPhone use for business. That was with limited browsing and no telephone calls (Note: paid-for report).

Apple is not alone. Microsoft had to fix its version of Exchange for push email on Windows Mobile because of a similar problem, according to Delaney. Firmware changes are likely to address some of the applications that drain the battery, and Apple urges users to keep the product up-to-date for this reason.

A firmware update could also solve the problem of dropped calls, although 3G experts are unsure whether the breaks in service are down to the wireless networks, the phone or interactions between the two. T-Mobile in the Netherlands at first blamed the phone, then claimed the problem is still under investigation. In the UK, O2 says it tested the phone extensively before launch but found no appreciable difference in behaviour to other phones.

Francis Sideco, an analyst at iSuppli, says Apple and others have to go further to improve the performance of handsets and make software energy-aware. As more people use the data services, they are going to find their handsets running out of juice unless the manufacturers can find power savings: "They have accelerometers in there, so they can detect if the phone has moved at all. If it hasn't moved, there is no need to get an update from the GPS."

With its $275m (£148m) purchase of chip-design company PA Semi in June, Apple indicated it wants to have much more control over the iPhone hardware and power efficiency is the most likely beneficiary.

Allan Yogasingam, technology analyst at TechOnline, says the purchase is a major change in direction for a company that prefers to use off-the-shelf silicon, often using older parts to keep costs down. Don Scansen, technology analyst at Semiconductor Insights, agrees: "Apple's value is all about the software. They don't need cutting-edge technology to do it."

Apple's decision to delve into processor design appears to be tied to an unusual licence deal that ARM revealed at the end of July. Apple will not say whether it took out the licence and ARM chief executive Warren East says the mystery licensee demanded confidentiality.

An architecture licence makes it possible for designers to alter the inner workings of the processor, although they cannot sacrifice binary compatibility with other ARM cores. Almost all chipmakers prefer to buy the ready-made designs produced by ARM. "We offer this as a choice," East says. "You can see by the number of architectural licences that we have that we don't go out of our way to sell them."

In 1995, Digital Equipment became the first company to buy an ARM architecture licence. The result was the StrongARM. This processor ran four times faster than the ARM processors but needed 40% less power to run each instruction.

Dan Dobberpuhl, a processor designer, led the Digital team up to its 1999 sale to Intel, where the StrongARM mutated into the XScale. Founding PA in 2005, Dobberpuhl recruited a number of the original project's engineers to help build the 150-strong chip-design company. Almost 15 years later, the PA team looks ready to repeat the feat.

Jim Tully, vice-president at consultancy Gartner, speculates: "If they found a way of really reducing the power dissipation such that other companies had to go to a new generation of silicon to get the same power reduction, that would allow Apple to stay on a lower-cost technology for longer."

Sideco points to the new generation of multicore processors as a way of making the hardware more efficient. Apple wants its Grand Central project to improve software speed on Macs by spreading the workload across processors. In a mobile device, there is another option. If each processor can run slower because many of them are working in parallel, you can design them to use far less power. And you can turn off processor cores completely if the phone is just ticking over.

Lower cruise speeds

"The car companies have done the same thing. If you are cruising down the highway, they shut down four out of the eight cylinders to save fuel," Sideco explains.

Designing the new processor chip will take time. Linley Gwennap of The Linley Group, an analyst, says: "For this sort of chip, it could take anywhere from one year to two years to get to having the first test chips. It's closer to three years before I would expect to see an iPhone that had any kind of Apple-designed chip in there."

The project could cost between $40m and $60m, Gwennap estimates, based on the amount PA raised from venture capitalists to design its first processor.

Despite the credentials of the PA team, Gwennap says it is hard to see how Apple could really steal a march on other experienced chipmakers: "There are a lot of smart people focusing on low power at a lot of companies."

By designing its own processor - possibly with many ARM cores onboard - Apple may be able to use its control over the iPhone software to achieve power savings that users of off-the-shelf silicon cannot. In the meantime, Apple will have to provide smarter software to deliver the battery life heavy users of the internet demand.