User's Manual

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5.8.3 Battery Selection
Whilst there are several rechargeable battery technologies commercially available,
including Nickel Cadmium (NiCd), Nickel Metal Hydride (Ni-MH), Lithium-Polymer (Li-
Polymer) and Lithium-Ion (Li-Ion), the only technology recommended and supported
for use with the GR64 is Li-Ion. Li-Ion provides a good combination of high energy
(3.7v) and long cycle life, which lead to low overall energy cost.
The weight of lithium ion batteries is approximately one half compared with a nickel
cadmium or nickel metal hydride battery of similar capacity. The volume of lithium
ion batteries is 40 to 50% smaller than that of nickel cadmium, and 20 to 30% smaller
than that of a nickel metal hydride.
The lithium ion battery is free from the so-called memory effect, a phenomenon
associated with nickel cadmium in which the apparent battery capacity decreases
when shallow charge and discharge cycles are repeated.
A single lithium ion cell has a voltage of 3.7V (mean value), which is equal to either
three nickel cadmium or nickel-metal hydride cells connected in series. This voltage
is close to the nominal VCC of the GS64 device.
Li-Ion batteries generally provide long storage life with few limiting condition, and
offer problem-free charge after long storage. Under normal conditions, the lithium
ion battery has a life of more than 500 charge/discharge cycles. Also, Li-Ion
batteries have a slow self-discharge rate (typically 1.3% per month, compared with
Ni-MH batteries which can exceed 50% per month).
Lithium ion batteries are environmentally friendly, inasmuch as they do not contain
any heavy metal pollution substances such as cadmium, lead, or mercury.
There are many manufacturers of Li-Ion batteries worldwide. Sony Ericsson make no
recommendations with regard to specific vendors, but here are some considerations
for GS64 users which may prove to be useful in the selection process and
implementation:
Li-Ion batteries marketed for cellular (mobile) phone use may make a good choice
battery manufacturers with heritage in supplying the cellular (mobile) phone industry
could make a good choice, especially for high-volume requirements
look carefully for batteries which are rated at temperatures that the GS64 is likely to
operate at (many batteries are only specified for -20°C to +65°C operation which may
not be sufficient)