26
Description
T801-4 Installation and Operation Manual
© Tait Electronics Limited September 2007
1.4
Back-up Battery
A 3V lithium battery (type CR2032) provides back-up power for the
optional internal GPS receiver. The battery provides back-up power to keep
the module’s RAM alive and to power the real-time clock when the
receiver’s prime power is turned off. RAM is used to store the GPS almanac,
ephemeris and last position.
Note
Configuration data programmed at the factory is stored in non-
volatile flash memory which does not require back-up power.
Although battery back-up power is not essential, using it can reduce the
time to acquire the first GPS fix:
■
hot start
less than 20 seconds (typical)
■
warm start
less than 45 seconds (typical).
Without battery back-up power, the GPS receiver, upon power-up, has no
memory of previous navigation data and must perform a cold start. In this
case the typical time to acquire a fix is less than two minutes. For more
information refer to
“GPS Fix Acquisition Times” on page 31
.
Battery Life
The lithium battery may last for up to two years, depending on how often
the GPS receiver loses prime power. However, we recommend that you
check the voltage output of the battery every year. The voltage must be
higher than 2.5V.
Replacing the
Battery
Follow ESD precautions during this procedure. Refer to
“ESD
Precautions” on page 75
.
1.
Disconnect the power supply from the T801-4.
2.
Remove the top cover.
3.
Lift the edge of the battery with a thumb or finger.
4.
Grip the raised edge of the battery with long-nosed pliers and slide it
out of the holder.
5.
Slide the new battery into the holder with the positive pole (+) facing
up.
6.
Refit the top cover and reconnect the power.