What’s with my Mitsubishi Space star?

Since yesterday had problems with the car BJ 1999, were today in the workshop, there it was said that the alternator is broken, new installation for 500 euros. Now I have after a few meters drive the same problem as yesterday. Every time you switch the gears down, e.g. because of a curve it goes out, but not always. Had after the drive from the workshop made another test drive, about 15 minutes, there was absolutely nothing. And I tested everything while driving. Now I am again drive, about 3 hours later and he went out again several times. Before mostly the battery light lights. What can that be now????