In reply to ablackett:
Thank you, and thank you to the others for replying.
So choosing a powerbank is the main thrust, I suppose. I have a couple of freeby ones, such as the one which is currently charged up from my laptop, but it is only 2200 mAh, and gives out a current of 1 amp when being used to charge something else.
So is the Anker the best powerbank to be packing in my rucksac, or do I keep it for the van, and charge things prior to heading across the hills/peaks? Possibly there is a compromise that is a quarter of the size of the Anker. (I am not averse to Anker, as I think that the bluetooth speaker made by them, that I possess is brilliant).
I liked the idea of a solar powered charger, due to having a power source for it, when the light allows, away from the road, and it sounds environmentally friendly, though now I'm not so sure, if you allow for the downside of the manufacture of i,t and the nature of its storage etc.
So not as straightforward as I had hoped for....