I have two at the moment and the Jeep was already all wired up for a dual battery setup but had no second battery, I tested it all worked and decided I may as well use it but didn't want a big battery back there with limited space
Better to be safe than sorry with the auto and no chance to push start
Testing with the motorbike battery, making sure the isolator works etc.
Also has an auxiliary plug wired to it.
Cheers
Steve