Good question. The answer above is a good one; however, those smart caps cost a lot of money. I am thinking of deleting one of the two rear seats, build a small drawer system that open up towards the door and on top of it mount a wood piece (covered in same flour mat as the one in your truck) that wheel lay flat on the rear wall that divides your trucks bed with the cabin.
Then, on that wooden plank you will screw in you 12v system making it very easy to check your battery status and troubleshoot anything that might be wrong with it.
If you get creative you may not even need to delete the rear seats. You can somehow mount it behind them depending on the space your truck offers