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94 Quick Guide for the Impatient User

So what’s with the “InfoLithium™” logo – is this just marketing speak, or
what? The answer is “What”, and to explain what it does let me share with
you what’s called a battery discharge curve in Figure 3-19. This
graphically depicts how much voltage the battery can produce as power is
drawn from it – going from left (fully charged) to the right (as the battery is
slowly discharged), you can see that the voltage the battery can provide is
relatively flat – that is, until the voltage drops suddenly and dramatically
near the right side (where the straight red line is).
This relatively flat voltage characteristic of Lithium-ion batteries (as with
their predecessors, the Ni-MH and the Ni-Cd recharagables) is a joy to
consumer electronics companies, who love a stable voltage until the battery
is almost discharged – this means you get maximum use out of the batteries
before they are depleted. (This was generally not true of the earlier
batteries, such as Carbon-Zinc and Alkaline.) The downside is, at least
until recently, it was difficult for a camera to ascertain where along the
discharge curve the battery was. (Well, okay, it wasn’t really difficult; but
the fact remains that nobody made much of an effort to even guess.)
Cameras and camcorders alike simply showed “Full charge” as long as the
battery’s voltage was above a certain threshold, and as soon as it fell below
that threshold (when the battery was nearly dead) the camera would provide
a “Battery Depleted” warning a mere minutes before it would be depleted.
This was hardly a warning at all!
So Sony invented the InfoLithium mechanism to allow its cameras and
camcorders to act more like a car’s gas gauge and less like a “3 minute
warning” display. And the mechanism is really quite straightforward:
Inside the battery there is a small memory chip. The chip knows when it’s
fully charged, and it knows what its total energy capacity is. During use
the memory receives power consumption information from the camera
continuously, and the memory chip takes note of how much power has been
extracted so far. The battery can then use this information to estimate how
much life remains (in terms of percentage). As the battery ages, the
memory chip notes the reduced capacity from last time and adjusts its
future calculations accordingly.
Unlike a gas gauge (which actually measures how much gas is actually
left), the InfoLithium mechanism merely provides an estimate of how much
power remains. This explains why you can still take a lot more pictures

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