12V, 24V, 36V or 48V. One 10 Amp Bank. Or applying AC power to your on-board battery charging system. According to the specs and literature, it's a smart charger. It charges when the battery falls below full charge, then monitors (without charging). Owners of bass boats and larger crafts are probably better served by purchasing an on-board battery charger like Bass Pro Shops XPS Intelligent Technology Series On-Board Battery Chargers or one from the Dual Pro, Minn Kota or ProMariner lines. On-boards tend to be more expensive than portables, but they easily pay for themselves in convenience.
I have that charger and it seems to work fine. It really has some nice features for the money like PM mentioned. I see now it's $179. I think I paid $159. This is the second one I have owned. The first one I had to return but it was my fault.