Friend recently bought a Catalina 34 Mk I - after his first sail, he found his batteries had gone dead. Batteries on board consisted of 2 size 24 deep cycles with an A/B/Both switch. Oh yeah, 12V refrigeration. Whoever did the electrical system on that boat obviously didn't care about the needs of the owner, only the bottom line. I recommended he go to a dedicated Gp 24 start battery for the diesel, and 4 of GC-2 for the house bank.