Spurtar Top Post Battery Isolator Switch 12V - 24V Kill Switch Battery Disconnect Terminal for Car Truck RV Boat Vehicles, 2PCS

Q: In the description it says "Brass battery switch made of heavy duty solid brass", but when I had to file down a rise, the brass came off?

If it says solid brass it should not flake off it should be brass through and through I would send it back mine is not like that

Q: How did you connect your original cable "to" this? Its just a hole on that end!

Your original cable should have a "horseshoe" fitting that attaches to the post on the battery (if not I am not sure what you would have or if this would work). That horseshoe fits round the post end (not "horseshoe" end) of the disconnect switch. Hope that helps.

Q: Will this work for a 48 volt golf cart set up?

Note the product description says it is for 6-24V. Sometimes switches can be used outside the design spec, but when used at voltages above spec it is possible to get arcing, pitting, premature failure, or welding of the contacts. I would look for a within-spec solution.