Well, made product works excellent at a very fair price.

I was worried about this because the initial voltage, or pressure is very high. Like I don't know 30 volts or more? But the bottom line is it doesn't actually push that many volts in when connected. Apparently it's smart and knows what to do. I hooked it up and left it in the sun while on a business trip for like 9 days. I was mortified that this was going to fry my battery. When I got home everything was fine. Turn the key and the engine spun like a blender. I would recommend these for vehicles that you are going to leave outside for periods of time that made drain by themselves. Business travelers, campers, things like that. I will probably buy one or two more

I bought two, put them both out in the sun for a couple of days for a trial run. Both put out 20+ VDC, both controllers cut off at approx. 13.6 VDC. Have one panel and controller in service for a couple of months now on a gate operator, good so far.

I have been using two of these for about a month now, and they seem to be working excellent. I had to charge a 12v mower battery (it was just low on 230 cranking amps) and it was back to full power in a day. And, yes, I have used the batteries after charging and they are working fine. I just use these to keep a couple of batteries ready for emergencies, and to run a 12v water pump on occasion. So far, it has worked perfectly for me, but it may not be the best option if you need a battery charged quickly. For just keeping a battery charged and maintained, which is all i am doing, it is working great.

Hooked it right up to a car battery and set it outside at noon on a sunny day, was charged in a couple hours. Stored in the shed, this still lights up as "in sunlight" just from the ambient light coming in through the windows. Quite a good solar panel.