How long can it be left on charge? when do I know it is fully charged?

SOURCE: What tells when fully charged?

On the Motorola H700, the light will turn from red to green.
link to your online manual
http://www.motorola.com/mdirect/demos/how2_h700/main.html

Good Luck

SOURCE: not knowing when my nuvi 250 is fully charged

if the greens bars on the upper right indicates fully charged

SOURCE: battery fully charged

thier is a pic of a batterty in the bottom right corner, it will be fully green when charged. otherwise it will be flashing.

SOURCE: How do I know when Jabra BT4051 fully charged?

I charged mine until the light went off

SOURCE: HOW DO YOU KNOW WHEN YOUR MP3 PLAYER IS FULLY CHARGED

That would depend on the make and model of the player. I know my MP3 player is fully charged when the battery gauge shows all green.