Battery Charging

I am looking at a TM (used) but whether I buy it depends on finances. I did not know much about them until reading this thread. I am impressed.
I have one thing to add here though.
I have never had a TT or TM but I have seen street rods with trunk mounted batteries and that relates to trailer mounted batteries.
If you run #4 gauge wire from your TV using a battery isolator you will keep each battery charging as needed only. Using #4 wire prevents voltage drop. Voltage drop will cause amperage rise in direct rate and that will cause problems.
#4 wire is big, but workable. Run it through the inside of the TV or through pvc under the TV. Water and corrosion causes problems under there. I have heard #4 audio cable is more flexible than other types but expensive. If you go to a welding supply store and buy #4 for welding, the price is right.
This way, when your alternator puts out the 14.8 volts it is set for, you will get a good 12 (or more) to the TM battery.