At your first large town or city, perhaps BEFORE YOU START, go to a ferreteria or China Bazar shop and buy a GROUNDED 3-way 'cube tap' or plug that converts one outlet to three. This way, you can convert the limited number of outlets available to share with two other people.
Your fellow pilgrims will appreciate the gesture. The grounded feature is likely required by your e-bikes charger transformer. Smaller, non-grounded plugs, will also fit this adapter.
I will not address the issue of using expensive electricity. That is a cost of doing business and running an albergue is a business. They might consider an extra charge for folks arriving with e-bikes as they know additional electricity will be used. One € should cover it. Even a donativo albergue should implement this optional charge, in my view.
The other charger uses for phones, cameras, tablets, etc. are so tiny as to be inconsequential, at least IMHO.
But either way, carrying a Schuko 2-pin, Euro style, 1 to 3 plug converter is a wise and friendly thing to do. I always carry one. I have several in a box at home and grab one before I leave for the airport.
One day, a few years ago, I came upon a heated argument over a single available outlet. Several folks wanted to use it and one person was 'hogging' it. I merely reached into the top pocket of my rucksack, pulled the 3-way adapter out and politely contributed it to the cause. I gave it to the one woman in the group and told her to keep it and use it to 'pay it forward...' I also suggested the others buy their own at the next ferreteria or China Bazar shop.
Note: I was not one of the folks involved in the argument. My phone was already fully charged (piggyback battery pack case). But, having one of these handy-dandy devices is a very good thing, and worth the few added ounces IMHO.
Hope this helps.