12+ Ah will be fine something in that range should provide 300-400 cranking amps be able to supply safely supply 14 amps for an hour continously, which will be more than enough. If money is no object and you want super light weight ie:2-3lbs a lithium motorcycle battery will fit the bill just fine. The AGM type batteries are available at most powersports places like a cycle, quad dealer etc. They are cheaper but a little heavier. http://shop.antigravitybatteries.com...teries-ag1601/ would be a good lithium choice.