What should I check before building around these used panels?

Start with the label on each panel and record its open-circuit voltage, maximum-power voltage, and current ratings. Then check each panel in good sunlight with a multimeter set to DC voltage. A voltage reading is a useful first screen, but it does not show whether a panel can deliver its rated power.

If you want to compare output, use a suitable PV tester or a meter and test setup rated for the expected current. Don’t put a meter in current mode straight across a panel unless you know the meter and procedure are appropriate. Also look over the panels and connectors for visible damage.

All 16 add up to about 1,808 W of nameplate capacity if they’re working and operating at their rated conditions. That’s not a promise of that much output in your setup, though. Figure out what you want to run and for how long first, especially if the loads include pumps or cameras that need power overnight.

Once you have the panel label values and your daily energy needs, you can choose a controller and battery that fit. The controller’s allowed input voltage and current matter, and the series or parallel arrangement has to stay within its limits.

I wouldn’t buy the rest of the system based on the model name alone. Confirm the ratings on the actual panels, see how consistent their test readings are, and check what connectors or extra electronics are attached. Don’t assume an unfamiliar box is required or compatible without identifying it.

For a first setup, keep the design simple and make sure the panel wiring, controller, battery, and any inverter are all rated for the voltages and currents involved. If you share the label values and what you plan to power, people can help narrow down a safe configuration.