Battery Setup

[pk]

Looking for a little feedback for my new wiring plan. My v20 is a 1987 with a 205 Mercruiser. When I got the boat it had two new group 24 deep cycle batteries connected together with one of those Off-1-all-2 switches. Last year, I started having issues with the batteries always seeming to be low on charge. Through the archives on this site, I have discovered a few things;
1) I need to get a battery isolator installed to allow continuous charging of both batteries regardless of the switch position. 2) I need to replace one of the batteries with a marine grade, regular cranking battery, not a deep cycle. 3) I need to isolate the power feed for my accessories and lights so that it comes from the deep cycle battery alone.
So, from looking at my wiring diagrams, I have a power feed that comes from the engine harness to the front of the boat. The power daisy chains through the various fuse holders at the helm. In order to isolate the lights & auxilary circuits, I need to run an additional feed from the deep cycle battery to power these items. The only items left on the cranking battery will be the ignition, blower, trim, horn, and bilge pump. Is this broken up enough or should I add some more items to the deep cycle circuit? Thanks.

[tsubaki]

Personally I'm a big advocate of all the system being operated by the same battery(s) with the switch being capable of changing the circumstance as I please. If there is an issue of dividing the battery loads then the problem arises of how to keep the nonchargeable loads charged.

[tsubaki]

The normal preferred situation would be only three wires going to each terminal of a single battery. The engine wire (usually a #4 Or #6), the fuse panel main feed (#12 or #10) and a fused bilge supply. Adding an extra battery cuts your chances of low voltage in half if you connect all the negative terminals together then connect the engine wire and fuse panel main wire positives together and to the load terminal of the battery selector switch. Then connect to the battery 1 terminal with a battery and to the battery 2 terminal with the other battery. The fused bilge terminal is only if the boat is to be moored in the water to be connected directly to either one battery. This way the battery switch can be turned to the off position when not being boarded and save battery life and also allow selection between preferred batteries.

[macojoe]

I have two of the best Car batterys installed. both toghter no switch. Never have a problem.

Now if you must have a switch then the way you want to go is fine.

But your battery selection is wrong IMO, You are running a starting battery and a deep cycle battery which charge differently

Deep cycle is made to charge and drain charge slow and long.

Starting batterys are made to never totaly discharge and charge anytime with the motor.

Everyone has a different way of doing it, I say use two smae batterys so they charge and discharge in the same manner, and you should be fine using thwe few things that you use.

If running a live well or something I would use a 3rd deepcycle alone and charge when I got home.

Do a search this has been talked about a lot latley!