Data Hacking

Power Hacks
Without power, even the best GPS receiver is nothing more than
just an interesting box that does nothing. Given that a GPS unit
has to pick up signals from satellites that orbit the globe at an
altitude of 12,000 miles (19,200 km) and complete two rotations around the
Earth every day, it’s easy to see why there is a fair amount of power drain
by the antenna in order to pick up and decode the signal. Add to that the
power load of processing the data and displaying it, and you see that two
or four small batteries aren’t going to last too long under these conditions.
This chapter describes some power hacks you can do to your GPS to
improve battery life, and how to extend battery life by making use of
external sources.
GPS devices that contain a rechargeable Lithium-Ion battery are
appearing on the market now. While this is generally an advantage,
it can also be a disadvantage if it runs out in the field and
you don’t have access to a suitable charger.
GPS Power Needs
On the whole, battery lifetimes aren’t that bad, depending on what batteries
you use. Most GPS receivers use either AA or AAA batteries, but not all
AA or AAA batteries are created equal, as you’ll see in the following
sections.
For more information on batteries, a good website to visit is
http://michaelbluejay.com/batteries.
Alkaline Batteries
A fresh set of alkaline AA batteries (see Figure 3-1) in a receiver such as the
basic Garmin eTrex will last approximately 22 hours, while the top of the
range eTrex (the Vista) will go through the same two AA batteries in about
12 hours.
chapter
in this chapter
˛ GPS power needs
˛ Portable 12-volt
supply
˛ Portable battery
packs
˛ Alternative power
sources