I want to add some extra hard drive but I don't think my current powersupply can handle it. The machine is an old mac so it would be problematic to upgrade the powersupply. What's the best way to power the extra hard drives?
More aboutbest power extra hard disks
You can power them with a second power supply. Just short the green wire on the big 20-pin connector to one of the black ones and the PSU will turn on.