The device just works. Plug it directly into the solar panel and it will get the job done. The 24V model has some sort of "hacking" transistor or something that's noisy, but it's not too bad. I had two jobs within a few months and no problems worth mentioning.
Keep Your Battery Fully Charged With A Smart 12V Charger/Maintainer Featuring Winter Mode
28 Review
Efficient Charging With LST 7 Stages 5A Battery Charger - 3.3A 12V For Ultimate Performance
35 Review
Xiaomi 70mai Jump Starter Midrive PS01
120 Review
70mai Jump Starter Max Midrive PS06 black
37 Review