Originally posted by: DaleHollow
I recently came by a marine grade 24 volt winch (free) for pulling the jet ski up the ramps.
I know a 12 volt system is the norm, Question if i purchase 2 new batts to create the 24 volts for the winch, can i pull 12 volts of the post set up some how with out a S/W or other extras?
Two 12 volt batteries in series gives you 24 volts. At the junction of the two batteries you have 12 volts that you could use, if needed. This would be a good source if you needed only a small amount of 12 volts, like for operating a relay or other control function associated with the winch.
If you want to put a significant load on the 12 volts, such as cabin lighting, then you would be far better to have completely separate battery systems. Like Willie said, it would be fairly easy to throw together a small 24 volt battery system and a trickle charger.
If you were intent on using your cabin batteries for the 24 volt source you could rig up a relay system that would provide what you want. Normally the two cabin batteries would be in parallel, and nothing connected to the 24 volt line to winch. Flip a switch and relays disconnect both positive and negative of one battery and reconnects the battery in series. Now you have 24 volts going to the winch. While in this mode you cabin has only half the capacity so only leave it in this mode as long as necessary. When you are done, flip the switch back and the batteries return to parallel connection. In parallel connection they will "equalize" and both batteries will charge.
The relays you need to do this will NOT be cheap, however. What you will need are a pair of SPDT (single pole, double throw) relays that has current capacity that is at least as much as the current rating on the winch.