Yes there is a small rechargeable internal battery (approx 3 volt), if it is not present or flat the Garmin will not boot.Try leaving the unit powered for a few hours and see if the internal battery recharges.
It needs disassembly , some patience , a steady hand and a soldering iron to replace the battery.
You can get a diagnostic screen by holding menu while you turn on the power , use menu to step through.
john B, April 2008
