[Q] recommend an external really high capacity battery

Hi All

Can anyone recommend a good solution for me.

I'm going on holiday for a week in a house with no electricity. I need some kind of a device that can charge my two phones and 1 Ipad.

It is possible for me to recharge the device a couple of times but I would rather not.

I have been looking at UPS solutions, but found none that I can be sure will charge USB devices.
I was thinking a modification for a car battery, but have not yet found a solution.

Maybe a +30.000 mah but they all seems to be fakes.

Can anyone recommend a good solution?

Thanks in advance

Morten