Still trying to figure out whether or not to bite the bullet and get a couple of Optima batteries. I saw some at Sam's today---their number was 34DC, but the specs are the same as the D34M --- 750 CCA, 120 RC, 55 AH. I'm running a 70# 24v trolling motor. Is this the battery I need, or do I need the bigger one? The price is 155.82, which seems to be a really good price compared to what I'm finding elsewhere.