Right, the Harbor Freight pump was just for doing a little testing.
I have a very nice pump already, but it doesn't have those handy garden hose connectors like the Harbor Freight pump does.
The pump that I do have is called an
El-Cid, and is designed for 12V solar. It's also a REALLY simple pump, so less possible future maintenance.
The downside to it is that it is NOT a high-head pump. It needs to run a pressurized system so that the weight of the liquid going out equals what's coming in, so it's not doing any of the heavy lifting.
I'll need a set of fill/service valves before I would be able to use that pump, as you need to be able to pressurize the line with the pump already in place.
I've seen a solar system charged with fluid before, and know I need to be able to do the same thing. In fact, I am the guy who shot and edited this video -
This one is actually a "cut-down" version of the video they have to train installers. The full video is about 45 minutes or so, and includes filling the system.