Charging system failure

I was driving at night and the radio went off, the headlights went out, it felt as if I had no power, but the van didn't die. The charging system failure light came on, also the ABS Service ABS light and the Battery Saver active light came on. I pulled to the side of the road and reved up the engine. I regained power again and drove home.
Next day, it left me stranded and only clicked when I tried to start it.
Replaced the battery and it started. Twice the Charging system failure light has come on at two different times.
I manually turn off the lights so as not to drain the battery while driving.
Could the alternator be bad, just charging intermittingly?