Better gadget battery-level readouts in pipeline
'Sh*t, it said full just now' - a cry of the past?
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.®
COMMENTS
who uses NiCd batteries?
Just how many devices use Ni-Cads these days? Manufacturers have gone over to Li-Ion mainly fpr safety reasons but also for density reasons (and possibly for replacement battery sales!)
Most devices use Li-Ion or NiMH. These have very different characteristics.
The biggest is that of internal resistance. This gets larger with age (and temperature) and is a big problem in high current applications such as laptops. They have no memory effect.
Even though an old Li-Ion battery is fully charged, it cannot deliver enough current due to high internal resistance. This gives very misleading results for remaining time and is a big problem for laptop smart batteries that are over a year old.
Phillips?
"A phone won't ever get as close as a phillips." Not even a Motorola Razor?
IGMC...
laptops and mobiles
Battery indication reliability isn’t so much of a problem for laptops/camcorders as it is for mobiles or MP3 players. The former don’t have significantly fluctuating loads, but the latter do (paused, display lamps off, not in a call). Hence a typical charge remaining indicator can easily be fooled when employed in those devices, but they are working in favourable conditions when used for laptops/camcorders so here they are of course more reliable.
The better indicators store the previous loaded voltage level so you are not fooled by the EMF when you first activate the device.
I wonder if this new system will give an accurate assessment of remaining charge without itself significantly draining the battery – well you can’t measure the impedance without taking current.
Battery memory
Hm... at least my HP Pavilion laptop battery suffered from the same evil, my solution was to use Linux, as Windows Power management would insist on shutting down at 5% no matter what I put on the settings. Which sucked when the battery started to die on me: I had about half an hour of actual charge, but XP insisted on hibernating.
Of course, now that charge is in the order of 10 minutes ... or less. APIC shows me only two values: 100% or 0%.
Old hat
Getting the power chip to measure Impedance of the battery is not new. My company has been developing a battery powered device with one of these chips for at least a year now.
It can also detect the type of battery attached and adjust the battery charging cycle accordingly. So it can take alkaline, ni-cad ni-mh, etc.
The technology is there and available for hardware developers, if only they'd use it.
;-)
