I have 100 AMP Powermaster alternator. I have SPAL 2700cfm electric fan, and A/C. With eveything on, including headlight, gauge shows little over 13. I do have it grounded with using a seperate 6 gauge battery cable. If I ever have to replace the alternator, I will go higher than the 100 AMP.
Jack

K.I.S.S.