Running Two Batteries

[Breadbocks]

Thanks for the input. For the record, in addition to a 4-cim drive base and a compressor constantly running, in addition to some other electronics, and the load is only going to go up once we add some other stuff that'll drain more power like a crapton of LEDs to make it pretty. I've had other 4-cim drive bases and the battery didn't drop anywhere near as much when it was running.

It seems like I'd want to either run an extra battery in parallel or a bigger deep-cycle battery. How expensive are decent deep-cycle marine batteries? Is there any reason to go with a better battery versus running a couple in parallel? I'd like to avoid spending large amounts of money if possible so being able to use old FRC batteries would be best.