I've been running a single 130AH AGM battery powering a 12v Minn Kota on my FC560 C/C for 7.5 years and it's still going well. AGM is much more forgiving than wet cell and gives many more recharge cycles even with abuse. You can get these from the Solar recreation RV companies for around $300 and needs no complex charging systems other than a smart charger. On the boat I have a VSR (Voltage Sensitive Relay) that switches from charging the starting battery to the AGM house battery depending on which needs charging.