charging batteries

hello iboaters, here is my question, I have a cabin cruiser that I keep in the water, I have two 12volt batteries wired together on one side of the battery swicth #1, and on the #2 spot on the battery switch I have a very large 12volt battery, looks like a truck battery, now I want to hook up a onboard charging system to them so I can plug it in when away from the yacht harbor is this considered a two bank or three bank???? and does anyone have any sugustions on how I should keep the batteries charged??

Re: charging batteries

You could always go the solar powered route if you have sunlight at your docking space

Re: charging batteries

thought about that, but its a covered berth

Re: charging batteries

Solar for that much battery is terribly expensive. With an on-board charger you can do what you want in either of two ways:

1) You can use a larger output two-bank charger (say 10 - 15A per bank). Connect one bank to the two batteries you have in parallel, and other to the large battery on switch position #2. Be prepared for a long discussion and various views on this topic. It's done all the time and is perfectly acceptable. Two batteries in parallel = one very large battery.

2) Use a smaller three bank charger, (say 10A per bank) and connect each bank to each battery. If the charger you buy has load sharing capability, the two banks connected to the two batteries in parallel will help each other as needed. As the battery they are dedicated to become fully charged, that output switches to help another output. If fact they will also help the third bank with the large battery.

Re: charging batteries

Thanks silvertip, I will get her done

Re: charging batteries

Silvertip said:

Solar for that much battery is terribly expensive. With an on-board charger you can do what you want in either of two ways:

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To Maintain two 12V Batteries, a 12 Watt Solar Panel Array ($170) should be plenty. Mayby $170 is terribly expensive but if you are just trying to maintain a charge with a trickle, even 4 Watts should work in full sun. That will provided 270 m.amps, I think...

Re: charging batteries

A 4 watt solar panel is nothing more than a "maintainer". It would take forever to actually "charge" a battery with that little power output. I have one in my shed to keep the tractor battery topped off over the winter. Other than that, they nothing more than a target for thieves.

Re: charging batteries

And maintianer is all you usually need to keep the battery/s fresh during storage. I use a 4 watt on each of my motorhome batteries, and they are always ready and in good shape when I am ready to go.