Isn't what we do to our units mostly for our own satisfaction! The costs of doing these sorts of things probably doesn't wash, except in the very long run MAYBE!! It is so we can do stuff where we want to do stuff. Can't you just start the truck and let it change the battery in the TC...all the solar and extra controls and batteries sure can buy a lot of fuel to run your motor if you have to.
I did that for a while once...the best investment was the remote start I installed when putting in the alarm...whole lot cheaper than other alternatives. Admit it we like doing Stuff for the fun of it and bragging rights!!!! NO???
Justifing only makes us feel good about spending the $'s!