To use a very old analogy...
Think of your battery as a bath, and your alternator as the taps.... When you open the taps, they fill up the bath as quickly as they can. When you use electricity, it's like opening the plug... the more electricity you want to use, the wider you open the plug. For a small load (like a CB) the plug is barely opened, so the water trickles out. For a large load (like a winch working hard) the plug is WIDE open and water drains quickly.
Now, the trick is to keep the water level over a certain level in the bath, else you run out of water. You can do this in a couple of ways...
1) You can increase the size of your taps... they will refill the bath quicker and cope with the loads. (Fit a bigger alternator)
2) You can increase the size of the bath, reducing the effect of the water draining out and giving you more time before the level drops too far (Fit bigger or multiple batteries)
3) You can reduce the size of your drain... (Use less electrical load, in this case a gentle pull uses much less power than a full-on recovery)
As Saffy says, to be able to give a specific answer, we'd need to know a bit more detail. What size is your alternator, what capacity (Ah) is your battery, how often you are going to use the winch and in what way.
If it's an M8000 (for example) and you have a 45Amp alternator... if you are just going to give yourself a little tug here and there in the event of getting bogged down on a track, then you'll probably be OK... if you are going to an off-road site and plan to get properly stuck, then you probably won't.
