I got a 14,4v 2500mAh batterypack(from two 6-cell NIMH batterypacks), the tube needs to be a bit longer to fit them how ever. 14,4v will give me 12-ish watts of RF output. Hopefully i can get a small solar panel to charge the batteries. I dont want a complicated charging circuit, but will look into a the possibility of using a relay to cut charging, or short the solar panel.
Without a solar panel the 6mA standby current would exhaust the battery after two weeks or so. Non-stopp TX with 50% duty cycle should last about three hours.
Thank you for the sudgestions on using a better amplifier, I know that there are better designs out there, i might continue experiment with other amplifiers as another project.