Re: Battery Switch and 2 Batteries...
I did not see anything from any of the previous posters that would require any of you to absolutely need a dual battery setup or a switch. Unless you have a killer stereo system with high power amps, a trolling motor, electric anchors, or any other high current draw items you simply do not need a switch. Many folks use them incorrectly anyway. Here's the deal. First, you do not need two new batteries when you install a switch unless they are due for replacement anyway. What size battery you use depends on what you run off of them. Obviously battery capacity (amp/hrs or reserve minutes) is the measure of that. More is better. You cannot go too big with batteries -- just too small. The difference in price is rather insignificant. Next, if battery switch use confuses you, then opt for an ACR (automatic charge relay) or VSR (voltage sensing relay) both of which do the same thing in that one battery (usually the start battery) is designated the primary and only it will be charged until the trip point on the ACR/VSR is reached. At that point charging switches to the secondary or house battery. If you do insist on a switch, then get over the notion that some things get wired to the house battery and only the engine stays on the start battery. Both batteries get wired to the switch. Everything on the boat except an automatic bilge pump gets wired to the COM terminal on the switch. Then whatever battery (!, 2, or BOTH) is selected is what powers the loads and the engine. There is absolutely no reason to be constantly messing with the switch. Set it to BOTH and go. If you do happen to beach the boat or run a trolling motor for an extended periiod, THEN switch to the house battery to save the start battery. Simple as that.