This was my wiring setup plans for using two groups of Trojan T105 6VDC batteries in series to give me a 450AHs battery bank capacity...

Some installers doesn't like my method of using frame ground to get my battery return cables connected but has worked fine for me over the years. I do use a separate frame ground connection for each cable.
My best move was to the BLUE SEA four position battery switches in my setups. In this drawing the battery switch selects BANK 1 or BANK 2 or both or TOTAL OFF.
In my other 12VDC Battery install diagram having two more of the BLUE SEA four position switches install gives the ability to connect to any one of the four 12VDC batteries or none. This is great for using alternate charging methods sometimes needed to charge some of the batteries when the other batteries are still connected to my setup and being used. I am presently still using this wiring setup but depending on my upcoming replacement batteries I may have to change my layout somewhat. My four 12VDC batteries were installed in late 2008 and I lost one right away because I let it boil out fluids on me before I caught it. Since 2009 after changing over to smart mode charging to last year I have been running three 12VDC Batteries but this season I have lost another 12VDC battery so down to two now in my setup (170AH capacity). Six years not bad for the abuse I have been giving my 12VDC standard issue 85AH GP24 Interstate batteries
Camping off the power grid with just a 170AH battery capacity battery bank is not doing well with me... I am carrying a second truck start 12VDC battery which I already had just for PLAN Bs...
Time to start looking for new batteries here... May add solar panels this time around as well... Solar panels should help out big time for when having to run my 2KW generator at 8AM each morning like I am doing now. My RULE NUMBER ONE is not ever start my day/night battery run unless my battery banks are re-charged up to at least 90% charge state.
Roy Ken