For the Boondocker folks that dry camp constantly... and need quick and dirty MANUAL bulk charging done to their batteries, the Power Supply units that go by the names of MegaWatt and Meanwell, as suggested by Mexicowanderer, deserves mention.
Value of bang per buck of this suggestion, is the best out there. Some Assembly required, some modifications might be necessary to customize to your exact needs. Porsche performance, at VW price points. But understand... if you can't drive a stick shift, and need an automatic, this will not work for you. Automatic is not an option. Emphasis is on MANUAL. The air gap between your ears will need to be 50% of the manufacturers recommended settings. Must use gray matter upstairs.