I've been using a Victron Blue Smart Battery Charger for the last few years without hassle. They're IP65 Rated, so the night time dew isn't a hassle.
I grabbed an accessory cable as well and made my own adapter using XT60 connectors for my scope setup. mainly because I couldn't be bothered to chase down the plug type they're using and didn't want to cut the cable on the charger.
You can set it up through Bluetooth to be a power supply, and you can set the output voltage. I've got mine set at 13.5V, and it's been pretty stable from my experience. I haven't put an oscilloscope on it to see how ripple free the DC output is, but it hasn't caused issue in the last 3 years.
Charger:
https://www.victronenergy.com/charge...t-ip65-charger
Fused Cable:
https://www.victronenergy.com/access...ctor-with-fuse
2m Extension:
https://www.victronenergy.com/access...xtension-cable
EDIT: They're kind of expensive, but a drop in the hat against what the rest of my astro gear is worth, plus I got discount at work.