These switches need to handle very high currents so choose a switch accordingly. It should be capable of handling well in excess of 20 amperes. Just check the specifications on any switch you plan to use. If they do not publish the specifications, beware. Note that there are two switch current ratings, continuous and switching. Switching current is alway the lower one as there can be lots of sparking and pitting just as the contacts are closing on a high current demand load. One with wiping contacts is better than one with just pressure contacts as they are somewhat self cleaning as the wipe tends to get rid of any pitting and corrosion.