The end of the mostly-useless battery fuel gauge?

I’m not saying that battery fuel gauge indicators on cell phones and MP3 players are completely useless – they do after all give a vague indication that the battery is mostly charged or mostly discharged. So I’ll equivocate and say they’re Mostly Useless. My cell phone, for example, spends most of its life displaying two bars, regardless of how much I’ve used it or when it was last recharged – it seems to feel that it’s not going out on a limb too much showing two bars.

The problem with battery gauges has been that their algorithms were too complex while their measurement capability was too simple. A battery gauge in today’s laptop or cell phone measures current, voltage, and temperature and integrates the current over time to find the charge. It has to model the cell’s reaction to discharge rate, temperature, and age as well as its self-discharge rate, and it has to re-learn the full-charge capacity over time. And on top of all this, it needs to predict and accumulate what the error is (it thinks) for all of these numbers. My cell phone’s gauge does all these, and then displays, more likely than not, two bars.

TI’s betting that user demand for more accurate gauging will make consumer electronic vendors eager to incorporate its newly-introduced gauges based on its Impedance Track technology. The new system-side bq27500 incorporates Impedance Track to directly measure the effect of discharge rate, age, and temperature on the cell impedance. This sophisticated direct measurement allows the gauge to calculate the effect on remaining capacity as well as full-charge capacity with no modeling/learning. Here’s the impressive number: TI claims a 99% accuracy in gauging remaining battery charge.