My portable setup, the way I want to implement it, will use a 20V weed eater battery.
Inside the package there are 5 LiPo cells. They have 4Ah capacity. I will use three cells to feed the power input and all 5 for PA power.
A DPDT ON-OFF-ON switch will do the power ON job.
One position 12V to both power inputs, one for increased voltage at the PA power input. Middle position OFF.
I think this will give me at least 5 - 6 hours of SSB operation.