Peter wrote:


How would the loss of the battery power prevent the GPS getting a
satellite lock?


It doesn't.. It legthens the time required to update its initial
position. Pretty much every gps, the first time its turned on, takes a
LONG time to obtain enough information to determine its current
location. The GPS cant tell you where you are going, or where you ARE,
unless it KNOWS where its been (even on a second to second basis).
Moving the box while this is happening lengthens that process.

If its moved more than 50 miles from its last known position (while
powered down) or if the "non-volatile" memory is lost for whatever
reason, then this LONG initial startup process occurs while box "finds"
itself. Not all of the data required for this is stored internally, and
if I remember right, is broadcast concurrently with the various time
differential signals that are used to compute the location fix.

As long as the machine REMEMBERS where it was, and its first signals
indicate that its not moved, the boot-up and acquisition process is
quite rapid.

For the average end user this is an issue that is never observed,
because this sort of thing is seen by the installer during installation,
or by the maintenance guy during update/replacement. Rarely, like when
the internal battery fails (after many years), an error message is
generated by the box that specifies the failure.

If you have an intermittent condition that isn't present on power up, it
may not annunciate it.

Good luck,
Dave