Battery - SL350F (self-fit for non-warranty replacement)

Your SL350D comes with a six month warranty on the battery and the unit itself has a 12 month warranty. If your GPS is more than 12 months old ie out of warranty you can just buy a new batttery online and replace it yourself. 

It's easy - you just use a small Philips head screwdriver to unscrew the 4 screws in the back to open the unit, unplug the old battery and plug in the new one - then screw everything back together again.