Battery disconnect

Tucked neatly inside the back of the plastic battery box, there's no chance of that happening.

 I use this one mounted on an auxiliary switch box, because it's waterproof (for salt water use) and both batteries are disconnected in the off position, they are not left in parallel. And if I ever had to remove a battery for replacement, it is relatively easy to unbolt the cable from the studs, and only run one battery.

 As mentioned in other posts, I do use both in parallel while camping, and when using the R-Pod inverter to charge, they are in parallel being charged together. 

 I bought it on Amazon. The first one only lasted one season, the internal plastic threads came apart. The new one is holding up fine so far.

I mounted a switch inside the pod in the compartment that holds the converter.  Works fine and very convenient to add one there. I mounted it inside so I have to open the compartment to get to it.   Got a cable and the switch at auto parts store.

Last year when I got a second battery I mounted another switch that has four positions...Battery 1, Battery 2, Both Batteries or Neither (disconnect).  This one is on the battery box.  It isn't really waterproof but that doesn't seem to be a problem yet.  To mount a four way switch inside the pod would require running another cable through the pod wall.  Didn't want to deal with that and the cable is kind of expensive for the length needed. 

If you are starting with two new matched batteries, only a simple disconnect may be all you need. 

I have heard on this site (after I bought the second switch) that I don't really need the four way switch as it is better for the batteries health to run them both together all the time......so I don't really need the option of running them one at a time. 

My batteries are the same brand and model but one is a year and a half older.....so I run them separate.  I understand that running them together will make the good battery to degrade to be like the older one. Not a problem if they are perfectly matched.....but an issue f they are not.       I use the four way switch and just have left the other one in the on position.  If I ever end up with two perfectly matched batteries the I will run them both on or both off all of the time.  I suspect that the battery life I would have lost is way less than the cost of the second switch I bought.   A simple switch inside the compartment holding the converter box...out of the weather.... is probably the way to go.  Unless TechnTrek or other people on here that know better than I do advise otherwise