what guage of wire for high ampage?

I have a 2003 Yukon XL, it now has a 200 amp alternator. I want to have 2 leisure batteries in the back which are connected to the wiring system to charge on my way to an event. I'm unsure what ampage is going to be drawn and what gauge of wire to use. As the batteries will be disconnected at an event and used in 24v. When I reconnect them I guess I'm going to get a surge. Is there something I can put at the front to limit the amps to say 60 ish? The car is about 20ft long so I guess about 25ft of wire will be needed. Any help and advice is greatly appreciated. Thanks Ben

4 Gauge wire is rated at 150 amps. 2 Gauge is rated at 250 amps. I do not know of anything that can limit the current to 60 amps.

I'd really like more info as tomwhat your hooking up and running on this setup. But you COULD use a 60 amp dc breaker and at LEAST 4 gauge wire but that's suggestive not knowing if its proper for what equipment yiur running. Plusnyou Should have NO surge when reconnecting the batteries if equipment is powered off when reconnecting.Gary Sather

No need to current limit the battery since you'll be using a battery isolator, hence they won't interconnect unless the vehicle is charging. Supporting and clarifying what tonanzith wrote, you should have NO surge when reconnecting the batteries if the vehicle is charging (wrt to charge currents and alternator capacity. The point is, one battery will then not discharge into the other). If you have a charge light, I'd consider the UIBI - a mere relay controlled by the alternator's charge light circuit. In your case, a smaller relay (30A etc) from the charge light circuit which feeds +12V to the heavier isolation relays - one between the main and other batteries, and one between the 2 leisure batteries (with fuses or self-resetting circuit breakers at each interlink end near each battery). Google "oldspark uibi". It's easy adding manual overrides. And you can leave the batteries in the vehicle for charging and top-ups provided the are suitably fitted & anchored.   Mind you, whereas wet cells are best charge by the alternator (unless you have a >20A charger), AGMs are best done by a suitable charge is they are very flat (hence drawing too much current which they do not like). PS - I presume you have >=200A wiring for the alternator with suitable beefed up alt/engine to chassis/body GND etc. Just because it's a 200A alternator does not mean it always supplies 200A (nor that it can at low RPM), not that it dumps all available current (100A or 200A etc) into the battery(s)... Batteries have their own current acceptance limits though often these exceed battery use/warranty conditions for reasonably discharged batteries. Usually tolerated for wet cells (eg, vehicle charging systems), many prefer to current-limit AGMs to their spec'd typical 10% or maybe 20% current limit for extra battery life (since overcurrent and "equalisation" damages AGMs).