Powerbank for travels

DIY powerbank - charging smatphone tablet or even laptop. Hi I want to build a Powebank for travel. My project must have capacity ¬50-100ah, for that i want tu use a lithium batteriesi don't want to use deep cycle battery because this project is for travelling, thats way a case for project must not be too large, i think smaller than 15.6 inch laptop. For now i calculate about ¬38000mah capacity from 1.5v 2900mah lithium battery. But i want to use better efficiency a lithium-Ion battery. Powerbank should be charged from micro USB cable and devices connected to powerbank will be charge with min. 1000mah and 5v thats way i think i need a power converter, and lithium battery charger. I want spend max. 50 pounds for this project. Stressing that it is for only travelling purpouse!