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Better gadget battery-level readouts in pipeline

'Sh*t, it said full just now' - a cry of the past?

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You know the way your phone shows a full battery for ages and ages, then as soon as you make or take a call it throws a double six and shuts down? Or the way your mp3 player drops towards empty while playing, then suddenly climbs up to almost-full again as soon as you press stop?

Annoying, isn't it? But, according to a report in MIT's Technology Review, such irritations could be a thing of the past soon.

Current devices suffer from misleading battery energy readouts because they typically measure only voltage. But batteries' output voltage drops when more load is put on them, which is the reason for the sudden plunge on taking calls - even though, in fact, it's unlikely that energy is being depleted so fast.

Furthermore, the voltage behaviour of a battery changes as it ages, which can lead power-management software to erroneously decide that there is no power available much too soon. In many cases, devices shut down well before they need to, and batteries with useful service life remaining get discarded.

"You can lose 30 percent of the energy in a battery simply because the device shuts itself down too early," according to Texas Instruments' engineers.

But the TI battery boffins reckon they've got the answer. The firm has produced a new battery-monitoring chip that measures impedance as well as voltage, allowing a more accurate assessment. The TI designers reckon their kit can tell within 1% just how much energy remains, perhaps allowing an increase in useable capacity of 50 or even 100% - dependant on power-management configuration, of course. The chip can be put in a device such as a smartphone, or in the battery pack itself.

According to TI, their new gear would allow a phone to tell users exactly how much talk or standby time was left, perhaps down to the minute.

An alternative approach is to measure current as well as voltage, which allows actual energy use to be monitored in real time. Provided the system has a good idea of how much energy was there to begin with, it will know how much remains.

Such voltage-and-current systems are under development by Motorola, among others. They would, however, need to be combined with an accurate model of battery-ageing behaviour to work properly, especially if the battery was charged up without being connected to the chip.

The Tech Review piece is here

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