Looking for battery disconnect switch recommendation

I installed one of these on my small boat, and will soon put one in my new trailer when I get a second battery. I'm old school and like to run on one battery, then switch to the backup so I can calibrate my remaining battery capacity usage.

http://www.amazon.com/Blue-Sea-Systems--Series-Selector/dp/B000K2MCR2/ref=sr_1_1?ie=UTF8&qid=1383935360&sr=8-1&keywords=blue+seas+battery+switch