I use a 3630 quite happily with a Navman3450 in the car. This causes no problems as you can plug it into the cigarette lighter.

No way without extra power will it last 9 hours if you leave the unit switched on. If you are simply going to turn it on anf off to check positioning etc you might make it.

The literature states battery life as 3 - 4 hours, however, if your 36** like mine is a couple of years old the battery will only last an hour or so.

Possble solutions to help

1 - Ensure you turn off the backlighting etc.
2 - Turn it on, check your position and then off until you need it again
3 - Replace the battery, they can be found as spares on Ebay
4 - Get an external battery - again found on Ebay for around £8.00 +P&P
5 - Get an external jacket with two CF slots and a CF GPS receiver.
6 - Using Tomtom 2 the whole of the UK (Roads etc) is around 90MB
7 - The Navman and Copilot maps are split so you can load only the bits you need.

Cheers