Powering GPS unit using external battery

[technik21]

I'm going to use my TTn3 & bluetooth Gps, on my motorbike to the south of France.
I don't want to use the bike's battery to power either the PDA or GPS, because of trailing wires. After all it is a bluetooth setup.
Now, because the journey time is going to be approx 9hrs, the internal batteries on both PDA & Gps aren't going to last the distance.
I tested both units to check on battery usage time, and found that the Gps unit will last for about 5hrs, and PDA about 6hrs +.
I have bought a "battery extender" gizmo to keep the PDA going (it's a 'battery' battery charger, which tops up the PDA's battery).
As for the GPS unit, I have a connection kit containing a power plug connector, which is itself capable of connecting to an external PP3 battery.
But before I test this, I was wondering if by connecting the PP3 (9v) battery to the GPS unit, is this going to damage the unit (I suspect it might), or will it supply the internal battery with power to extend the usage.
Am I right in thinking, that as both the mains charger and the car kit have inbuilt converters, then simply using a 9v \ 12v battery as an external source, just won't work.

I may have answered my own question!!

[MrT]

The TT bluetooth unit is 5 volts and has no internal regulator.

The TT cigarette lighter cable and the TT cradle both have regulators in that theoretically work from 7 to 40V and output 5V and you may be able to power these from a PP3 battery with a suitable connector. I don't know how much additional power they drain, but it is probably not much.

I would have thought that your PDA's battery-battery charger could be used on the TT bluetooth as it will probably have a 5V output and a similar plug. My iPAQ charging devices also work with my TT bluetooth.

A device such as this may also work:
http://www.globalpositioningsystems.co.uk/viewprod.php?product_id=1826 but you will need to check voltage and plug size.

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