Dual battery wiring help please (cooler boom box)

[LDC2335]

So my cooler stereo runs for a good 6 to 8 hours at lower volumes, but I'm going to need it louder and longer for an occasion coming up.

Can I wire an extra optima I have to it like this? I guess it's considered parallel. Right?

 

[Coxy]

Yessir. As long as you're positives are together, and negatives are together you are golden.

 

[LDC2335]

Sweet thanks. I was about 90% sure. Just didn't want the other 10% to be an exploded battery.