Ok, seems like the horse is nearing the point of being beaten to death? So if we combine all the good thoughts mentioned and I add clarification to my opinions...
A single battery, preferably an Optima 1000 CCA Red-top (start) battery, on a truck with a newly acquired winch is acceptable for use under the following conditions:
1) The battery, alternator, and electrical system are in good repair, ie properly installed, working, semi-clean, and with cables and connectors appropriately sized for the application.
2) The owner/driver uses common sense while wheeling in regards to wheeling in his/her skill level, wheeling within reasonable proximity to the capabilities of the vehicle (stock DD, mild build, truggy,...), and knowing the appropriate use and limitations of the winch and electrical system (see note 3).
3) Keeping unnecessary gee-gaws turned off.
4) Winch in shorter intervals (as safety allows) with pauses to allow the battery recharge.
5) Keep an eye on the voltmeter to be sure the alternator is charging and the battery is in condition to allow restart to prevent being stranded; bring jumper cables to restart if you've got friends.
6) If you ignore all previous 5 notes, be sure to bring the phone number of someone with a tractor
Please feel free to add and/or change
As far as the electrical loads other than starting and winching... most of the items listed aren't an issue. Engine management systems on newer vehicles require very little power; while they do control more, the electronics are far more efficient. While there are plenty of listable items that should be on in different circumstances, some are necessary for safety (lights, wipers, windows), some are for comfort (blower motor, heated seats), and then the rest. Of course at night in the rain or snow the lights will need to be on. A set of headlights don't add a significant load to overcome the one-battery idea. The rest are a function of duty cycle. Yes, wipers and windows and locks draw power, but you can't possibly push all the buttons to operate each continually and still run the winch. They draw a small amount of power for a few seconds and thats it. Sure wipers are on longer, but still not a considerable load. As far as the stereo- having it on at reasonable levels, even with an amp, while winching shouldn't draw much; however, if the stereo and 1K watt amp is causing the lights to dim with the bass on your favorite Tupac song, then yes it may cause recharge problems. But the more likely problem will be not hearing your spotter scream as you winch over him
.
So to answer the gee-gaw question: if there are enough electrical doodads plugged in to cause a large draw on the battery (aside from the winch), than yes you do need two batteries. But not for the winch... for all the doodads. There are plenty of things that can draw power without being a safety issue while winching- extra lights, gps, Ham/Cb, etc. Adding a second battery for them is a great idea; that will isolate them from possible electrical problems and keep them from dropping off when the battery voltage drops during winching and starting. I was reminded of the importance of isolating and properly wiring the electronics when a safety notice showed up a few weeks ago for my wife's V-dub. They asked that you turn off the heated seats while cranking the engine; it doesn't take much imagination to consider the ramifications to one's backside if the starter current finds a happy path thru the seat heater
! Yeeeeoooow. Adding (and properly wiring!) a second battery to operate extra lights, nav system, inverter, will keep them from rarely (but possibly) meeting a similar fate.
So in conclusion
, a winch used properly with a single, healthy battery should be more than adequate. A second battery is a great next upgrade though. I recommend the winching article in Overland Journal, Spring 2009 by Bruce Elfstrom. Great read! 
A single battery, preferably an Optima 1000 CCA Red-top (start) battery, on a truck with a newly acquired winch is acceptable for use under the following conditions:
1) The battery, alternator, and electrical system are in good repair, ie properly installed, working, semi-clean, and with cables and connectors appropriately sized for the application.
2) The owner/driver uses common sense while wheeling in regards to wheeling in his/her skill level, wheeling within reasonable proximity to the capabilities of the vehicle (stock DD, mild build, truggy,...), and knowing the appropriate use and limitations of the winch and electrical system (see note 3).
3) Keeping unnecessary gee-gaws turned off.
4) Winch in shorter intervals (as safety allows) with pauses to allow the battery recharge.
5) Keep an eye on the voltmeter to be sure the alternator is charging and the battery is in condition to allow restart to prevent being stranded; bring jumper cables to restart if you've got friends.
6) If you ignore all previous 5 notes, be sure to bring the phone number of someone with a tractor
Please feel free to add and/or change
As far as the electrical loads other than starting and winching... most of the items listed aren't an issue. Engine management systems on newer vehicles require very little power; while they do control more, the electronics are far more efficient. While there are plenty of listable items that should be on in different circumstances, some are necessary for safety (lights, wipers, windows), some are for comfort (blower motor, heated seats), and then the rest. Of course at night in the rain or snow the lights will need to be on. A set of headlights don't add a significant load to overcome the one-battery idea. The rest are a function of duty cycle. Yes, wipers and windows and locks draw power, but you can't possibly push all the buttons to operate each continually and still run the winch. They draw a small amount of power for a few seconds and thats it. Sure wipers are on longer, but still not a considerable load. As far as the stereo- having it on at reasonable levels, even with an amp, while winching shouldn't draw much; however, if the stereo and 1K watt amp is causing the lights to dim with the bass on your favorite Tupac song, then yes it may cause recharge problems. But the more likely problem will be not hearing your spotter scream as you winch over him
. So to answer the gee-gaw question: if there are enough electrical doodads plugged in to cause a large draw on the battery (aside from the winch), than yes you do need two batteries. But not for the winch... for all the doodads. There are plenty of things that can draw power without being a safety issue while winching- extra lights, gps, Ham/Cb, etc. Adding a second battery for them is a great idea; that will isolate them from possible electrical problems and keep them from dropping off when the battery voltage drops during winching and starting. I was reminded of the importance of isolating and properly wiring the electronics when a safety notice showed up a few weeks ago for my wife's V-dub. They asked that you turn off the heated seats while cranking the engine; it doesn't take much imagination to consider the ramifications to one's backside if the starter current finds a happy path thru the seat heater
! Yeeeeoooow. Adding (and properly wiring!) a second battery to operate extra lights, nav system, inverter, will keep them from rarely (but possibly) meeting a similar fate. So in conclusion
, a winch used properly with a single, healthy battery should be more than adequate. A second battery is a great next upgrade though. I recommend the winching article in Overland Journal, Spring 2009 by Bruce Elfstrom. Great read! 
