Wayteq 950

Hello guys!
here is the problem:
I have a V7 powered by a battery. The V7 supplies power to the LX COlibri logger and to the Wayteq 950 PDA running SeeYouMobile. The PDA gets the GPS signal from the Colibri through the V7. It's a very nice setup.
During my last flight the battery died after about 3 hours even if I've charged it 2 days before that flight. The vario went silent, the Colibri stopped logging and the PDA had no more GPS signal. Is there any possibility for the PDA to swap to the internal GPS if the Colibri stops without me having to go through settings and select a different COM port?
Also do you think it is a good idea to use the main battery for the vario also? So far that battery powered the radio only. I would like to keep the weight to a minimum.
Regards,
Eurofighter