Underdrives/electric fans

i wanna get underive pulleys for my truck but am not certain on gettin just the crank pulley or the crank and alternator pulley. I have heard that these pulleys can cause a drain in electrical power and also that they will make your engine run hotter. Also and partially to combat the over heating i would like to buy flex-a-lite dual electric fans...but i dunno if all that juice used to spin the fans would be too much for the power robbed from my alternator. I dont think it will be a problem at all tho cuz my engine bay has a dual battery holders and i only have one battery so if i buy another if should stop that problem from ever happening. all sound like a decent plan?

If you really believe that you want the underdrive pulleys, I would suggest leaving the existing clutch fan on. If the engine has an overheating problem, try a 180 thermostat and/or a new temp. sensor and switch. All that for under twenty dollars.

It will run hotter if you go with the crankshaft pulley because everything else will be slower, including the water pump. If you only change the alternator pulley, you should be fine for overheating, but the engine will have to turn faster for the alternator to put out the same amps. (would probably be ok as long as you don't run a big sound system) Dual batteries would not solve the problem, unless you charged them every night. The alternator is what produces the power, all the battery does is provide power to start the truck. Also (I assume you're doing this for more power), the added weight of a second battery and cables might add enough weight to cancel out the horsepower gain.

I was told by a mechanic who is a friend of the family that electric fans cool a whole lot better than any clutch fan ever would but they will draw down on the electric which will be even more decreased by the pullies. And i have no rediculous thumping sound system or any other power using item that is out of the ordinary. so maybe if i do notice a severe decline in electrical power ill get a more powerful alternator.