Constant Current Power Supply - 13.8V 8A

You state “This can be used for charging Lead Acid batteries similar to the one we sell but requires good knowledge of how to do so” Where do I find “how to do so” information? Do you have a video or document showing how to use this?

It outputs a constant 8A current; it means to not charge a battery that cannot accept that many amps; charging a battery @ a higher rate than it is rated for can cause hotspots/fires/etc

Check out a youtube video that covers charging circuit basics

Charger modules for 12V lead acid batteries are cheap, readily available, and unless you really know what you are doing, much safer to use than a constant current power supply (since that will required additional electronics to control).