wondering the same myself... have LS1 fans waiting to go on with BBP harness but i currently have just a 400w system and gonna eventually go to 600w and wondering if stock alt can handle it or bigger.

 

I'm running the 05 efans with a 145amp alternator, and tdrumm used to have 05 efans with a 105amp alternator...or trucks reacted exactly the same when the fans hit on high with the ac on.

 

RPO code for 145A alt?

 

The only problem I had with my 105A alternator and e-fans was the headlights went brown when the fans kicked on, and the alternator had a little fire in it when it failed. Other than that, it almost kept up.
It seems like the OEM fans must not draw as much amperage as my Spals.

 

When both fans come on high (when ac compressor engages), my lights will dim and voltage will just dip for a second. It used to be worse when I had my old PCMforLess tune, but I told Justin about it when I ordered my BlackBear tune and he seemed to fix it up pretty good