I am building a detatched garage about 75 feet from my attached
garage. I have my main panel and a sub panel beside each other in my
attached garage. The sub panel only has my small upstairs heat pump/
air conditioner for a bonus room hooked to it as well as a 50 amp plug
for a small welder I almost never use. Can I run a sub panel in my new
detached garage/workshop from the sub panel in my current attached
garage?

If so, do I need another ground rod at the detached garage?

If it helps, I can remove the 50 amp welding plug because I only plan
to wel in the detached garage anyway.

I have 200 amp service in my main panel. I think the sub panel next to
it I bought was either a 50 or 100 amp panel but like I sais, the only
thing on it is the 1.5 ton heat pump. It is usually turned off as the
upstairs is a play room for the kids.

I added the sub panel because all of the breakers in my main pannel
were almost full.