I came across these units and I think with a few little additions (a box and some nice terminals) they make an incredibly useful thing for any workshop or overland vehicle.
They accept inputs from about 6v to ~36v and can output 0.6v - 36v at up to 5A with current control / protection.
NOTE it's important to look for the DPH not DPS type, and/or specifically the BOOST capable (often listed as Buck/Boost or “step-up”) type, as these can boost voltage as well as drop it as the name suggests. This means you can generate 13v to charge a car battery from a 6v scooter battery just as easily as a 24v truck battery.
These units (DPH5005) are available for around £20 on ebay, they're very small, are easy to fit into a control panel or small box and can cover a whole range of electrical scenarios;
Someone has even created updated open-source firmware for them, and there's a fork of it that has a specific battery charger mode too.
I've seen similar modules sold as WZ3605E too.
There's similar modules with a less colourful screen sold as SK35H, or in full “SK35H CNC DC-DC Buck Boost Converter Adjustable Regulated Power Supply Module” or some combination of all those words jumbled up and pasted.