Here’s a large batter pack that you can travel with and even attach solar to. It says it can power 2 laptops, 4 tablets, or 8 phones. I have had it for five years and honestly haven’t used it more than once or twice. Since it’s a battery there will be slight degradation, so the useful capacity is likely between 85-90%. The new version of this is currently selling for $250 on the GoalZero website. It’s currently charged so you can test it.