Yes, the little solar chargers are low amp, but do have diodes to prevent discharge when there is no sun. This application does not need a charger, it needs a maintainer to KEEP the battery charged when not in use. This maintainer will do that if the collector is placed in a brightly lit area.
Typical wet cell batteries lose 0.5 to 1% of there charge per day if hooked to nothing, and modern vehicles have constant low amp draws such as clocks, computer memories, and alarms, so the batteries go dead quicker than older cars. When I was doing road service I had customers who traveled often who called for jumps every time they were gone for a couple weeks or more. This is 100% normal of newer vehicles.
The solution is a low amp maintainer. Solar works great, and though direct sunlight boosts the output, there is some charging even on a cloudy day. Solar won't work in a garage unless you have a window. Plug in maintainers also work great, but if you park in the drive the wires can be a tripping hazard. Being in Texas, you could hook your bicycle generator up to your windmill to keep your vehicle battery charged. You could hook up your stationary bicycle to a 12-volt generator and get something out of your exercise. There are dozens of ways to get it done. Do one that works for you. If you are blessed with sunlight the solar charger is good. It is the easiest for me.
The $24.99 solar maintainer is cheaper in the stores. Same thing I have. Works great. I've never seen a vehicle that the cigarette lighter socket (not "power outlet") is switched. Not saying such a thing doesn't exist, just that I've never seen one. Even if your vehicle does not have an unswitched lighter socket, it would be very easy to pull a wire to an "always hot" terminal in the fuse panel.