Portable speaker system is only as portable as the length of extension leads! Is there a solution to be able to use a portable power supply Wattage?

Help please. We have a PA speaker system we use for events in work but it is only as portable as the length of the extension cable! How can I use this in the middle of a field? Can I buy a portable power supply and if so what wattage conversion would I need for say 800 watts speaker system. Or would I need a power invertor to a leisure battery? Again what size?
 
Welcome to the forum!

Talking about length, that's a mighty long thread title! 😉

Details of your PA speaker system (make and model) would be helpful in determining its average current draw ("800 watts speaker system" is not particularly meaningful in this context.)
 
I've extracted the relevant information from your link for easy reference:
  • Dynamic: 400W (200W + 200W)
  • Continuous: 360W (180W + 180W)
  • Power Requirements: 100V - 240V, 50Hz/60Hz
  • Power Consumption:
    • Idle: 30W
    • 1/8 Power: 70W
 
From Yamaha Stagepass 400 page:
  • Power Requirements: 100V - 240V, 50Hz/60Hz
  • Power Consumption:
    • Idle: 30W
    • 1/8 Power:70W

  • so possible 70*8=560W maximum consumption, full blast.
    After all, you will use it : "in the middle of a field" and that means high power.

    As mentioned above, batteries won´t last long, it is very common to use a small gasoline generator.