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I've used a couple for Raspberry Pi projects, but those were essentially just a a step-up and a diode plugged in to a LiPo. I doubt I could make a proper, safe board for higher power stuff any better than the Chinese. Maybe the best bet is to cannibalise a USB power pack?
Also, they do already make laptop power banks. I don't ever want to dissuade someone from making something themselves, but I use a Poweroak K2 which is 50kmAh and does 100W. It's nice. It's also about a hundred quid, mind.