Rhodri Marsden: Why don't batteries last as long as they're supposed to?

As much as we can be certain of anything, we know that there are 100 pence in a pound, six eggs in a box and 53 seats on an executive coach. But one hour of battery life in a cutting-edge gadget contains substantially less than 60 minutes – to a point where the word "hour" has become as meaningless as, I dunno, "squilp". We're proudly told how long devices will last on standby, which is like talking about the durability of tyres based on a period they spent lying gently on big blobs of cotton wool. I don't want to know that an iPhone will last for 300 hours if it's left lying on a window sill; I want to know how long it can perform everything it's capable of before collapsing from exhaustion.

Nigel Dessau, the senior vice-president of microprocessor supplier AMD, made a rare admission last week – that his company was "not being entirely honest" about battery life – and called on the industry to re-examine the way it presents this data. The problems are obvious: first, manufacturers are reluctant to initiate a more honest system, because it'll make their products look pathetically inadequate; second, because we use gadgets in such different ways, coming up with accurate figures is impossible. But we're not necessarily after accuracy; all we want is something realistic – because the current rule of thumb (take a laptop's supposed battery life and halve it) is absurd. Currently, the only way for us to assess battery performance is to listen to the reviewers who have properly put these gadgets through their paces.

Battery technology is having trouble keeping up with everything it's meant to be powering, but there are ways we can minimise the impact. Keep your phone on G rather than 3G if you're not using the internet, and don't keep it in your pocket (apparently a cool battery is happier than a warm one.) Screen brightness is a power hog on mobiles and laptops, so turn it down, and turn off any features such as Wi-Fi, Bluetooth or GPS that you're not using. Of course, this is a drag, but just imagine: by the end of the decade we might even reach a point where we can watch a 90-minute DVD on a laptop without running off to find a charger.

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