Enough of wickedness, here the test result with HTC Touch Diamond (also XDA Diamond):
Runtime with active TomTom navigation, display 100%, only internal battery: 1 hour 45 minutes..
With full battery int + 4420-Pack:.. 4 h 50 min.
The runtime increases in this combination so to 3 hours. Sufficient for most motorcycle tours, a bit more but I had already expected. Therefore 1 point deduction.
That the part needs> 5 hours loading, there the 2nd stage trigger. And that no AC adapter for charging this is (is via USB charging).