Garmin GPS--low memory battery
Bruce, I have exactly the same circumstances (Model 48, internal ''low battery'' message, need to return it) but my experience has been very different. Perhaps this will help.
First - and I couldn''t find this info until it was offered by email from Garmin - you want to load your 48 with new AA batteries and let the unit sit for a week or so, then turn it on to see if the battery message has disappeared. There is a small circuit that allows the internal battery to recharge from hi-voltage AA''s but this circuit apparently has not served Garmin well. Like me, you may have already found this ''recharge'' has not happened.
Second, for the circuit reason above, the repair you seek is free. You didn''t mention it in your thread and I think it''s fair to note that Garmin, for a design intended to insure a always-working internal batter but which failed, they''re standing behind their product.
I would recommend you insure your email is addressed to firstname.lastname@example.org and address the subject line ATTN: C.S. Wheeler. S/he has been very prompt with all my queries on this as I was troubleshooting it, and the RMA # was sent within 4 hours of my reporting the recharge cycle had failed.
Good luck - to both of us - on this fix.