I have had the same experience with cheap tools.
"OF" [It'll be quite inefficient of course if that matters (like when camping).]
What do you or "OF" recommend?
Yup, watch out for heat, it points right to where the losses happen. Some are OK of course if handled right.
As far as a charger for auto use, the car cord is the obvious choice, zero loss but needs an adapter to match the socket on Solo (unless you buy the factory cord of course), both the cored and adapter are five bucks or so from Jameco.
For PA use, I think the regulator scheme I'm playing with is the call. Hands down. Small, cheap, efficient and almost bomb proof (it includes short circuit, overtemperature, reverse polarity and all the nice protection features). Right now, I've got the only ones of course, but through Pipes that might be changing soon......if we all think pure thoughts and vape a ceremonial bowl of top shelf bud. I'm doing my part there, are you?
OF