John Nall wrote:

> Except that after he gave it back,  the owner found that all of the GPS
> numbers had been wiped out.  (The GPS units are connected to the 12 volt
> battery system).

I think the possible answers depend a lot on how exactly it is connected to
the battery -- both in your friend's friend's boat, and in your friend's
boat.

All answers so far point to battery-backed storage and bad backup
batteries. However, if the GPS unit is connected to a switched battery
connection and frequently disconnected from the battery for a long time, it
is unlikely that your friend's friend's unit had a problem with this that
he wouldn't have noticed earlier. Possible, but pretty unlikely. In this
case it is quite unlikely that it would have lost the locations due to
being disconnected while moving it.

Now if it is connected to an "always on" battery connection on that boat,
then of course the bad backup battery theory is quite likely.

Gerhard

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