So, in a nut shell, if I was to get a winch fitted I should buy a deep cycle battery (yellow top) and parrallel connect to orig landy battery.

Use the yellow as the secondary batt. which powers the winch.

I could simply connect in parrallel so both charge on normal daily use, connect the winch to the yellow top, then, when using the winch, cut the conncetion between the two batt. and use the yellow top standalone?

Yes, you could do that, but if one of your batteries goes down, it will take the other one with it. It's better to fit a split-charge system like this -

X-eng High Performance Off-Road Engineering

I decided to just purchase two new yellow top Optima's. One replaced the original and does nothing more than power the car's usual system as per standard.

The second or 'aux' is connected to the winch/electric cooling fan/alarm system/fridge/CB ect.

The aux is charged by an X eng relay, this works by sensing the charge from the alternator, when the engine is running the aux is charged but as soon as the engine is switched off it is isolated.

I see the adavantages as follows:

1, As the standard fitment battery only works original fittings any faults are easier to trace.

2, In the event for example the electric fan which can run on after the engine is switched off develops a fault and stays on it will only flatten the aux battery. If the fridge is forgotten and left on over a weekend for example again only the aux is affected.

3, As the batteries are isolated before the engine is started it is simple to wire in a separate volt meter for each individual battery via the auxilary on the ignition. Indication of battery charge comes only after removing the charging source for a few hours. Once in a while I just switch the aux on the ignition but not start the engine and check the voltages are similiar. Remember you cannot use a specific gravity meter on a sealed battery.

4, In the event you find you have left your lights on or the main battery has gone flat for whatever reason you can simply jump start yourself. I tend to go off road in some quite remote places and to be stranded because of a simple battery failure is not something I would like to experience.

No doubt there advocates of other systems but in my opinion when it comes to reliability and ease of use i.e. fit and forget this is a case of 'less is more'

regards

Dave