Installed a new alternator and battery. Alternator was bad and the battery was getting weak. Both were exact replacements. When I did a test run everything checked out Alt. Putting out 13 volts. Flew from Colorado to Rock Hill SC. During the trip upon startup, I experienced an immediate shutdown and restart of the efis and radios. I notice low voltage once and increased the rpm, that seemed to help the problem. At my second stop 5miles from the airport all the electrical systems failed but I was able to restart them and land safely. On the last leg , I turned off my back up battery switch and had no trouble. I will be checking gound wires and connections before I start back to Colorado, but would like to hear any troubleshooting suggestions.