Question on my Dual Battery Setup

[alleymize]

I currently have a I/O Chaparral, 1988 version. I am adding a second battery with a battery switch that is the 1, 2, Both, Off type. I am using this diagram to set it up - http://continuouswave.com/whaler/reference/graphics/dualBatterySglEngine441x370.gif

My question is about the accessories and such. I want to use one battery for starting and one for when I am sitting without the motor running for accessories. Currently there is one large wire on the positive post of battery one and then have one large and several smaller, I am assuming for accessories that have been run prior to me owning the boat, on the negative post. If I hook the second battery up like the diagram, will the batteries allow me to work in the fashion I am wanting? I see that the negative posts of the two batteries are jumpered so that means I do not need to run extra wires to my second battery for the accessories right? If I understand the diagram correctly I basically could use either battery to be my accessories battery and then just deem the other the starting battery right? Or will they both be going down if I am using accessories in this setup no matter which spot I put the battery on?

Also, I do have two trickle chargers that when I get the boat home or it sits on the dock that I plugin and plan to put on each battery. Do I need to do anything special when doing this? I think I would want the switch in the off position but just wanted to check so I do not ruin my batteries.

Thanks ahead of time for any help and insights.

 

[tpenfield]

Set it up like the diagram and use the switch for selecting the battery to use for the various situations. That is what the switch is for. Also, keep in mind that some things, like bilge pumps, radio memory, etc. are directly connected to the battery so that they will have power in all cases. A good idea is to switch the ' both' when the engine is running so you charge both batteries, then switch to one of the batteries when the engine is off and you are using accessories, and such. That way you will avoid the risk of running both batteries down, if using too much power cuz the accessories (radio).

 

[alleymize]

Thanks for the reply and that is what I thought was the scenario but just wanted to make sure. I have also read in a couple of other posts that having the battery switch on both while the engine is running could charge both batteries. The batteries I have are both deep cycle and 12v obviously but one is more the size of a car battery and one is the longer deep cycle, is this still ok and is there any special instructions when I am putting them on the trickle chargers at home? Thanks for your help and guidance again.

 

[bruceb58]

If you use that type of switch, you can't separate engine and accessory loads. You would need a different type of switch.

 

[alleymize]

Yes, I realize it is not a "true" accessories only and engine only, it is more of a I am using this battery or this battery depending on the situation. I just want to make sure that is really the case. Even though both batteries are on the same wire on the negative side, a battery is not being used until the current or whatever comes thru the positive side correct? And that is controlled by the switch right? I mean the two batteries are not being drained together are they since they both have the same negative right? I am not an electrical person, thus my questions just to make sure I understand correctly. And no one has answered about if I am hooking up a trickle charger on each do I need to do anything special when charging them at home with this setup. Thanks for all your help.

 

[tpenfield]

sometimes it is best to thing of electrical circuits as if if were plumbing and not wires.

If your "+" and "-" are not connected, then no draining of the 'tub'. So, yes to your question, tying the "-" side of the batteries will not drain them, it is only a matter of which battery (ies) is/are connected via the switch.

 

[alleymize]

Awesome and thanks for the reply. So do I need to have a cutoff on the negative side when I put them on the chargers at home in the driveway or should I be fine just hooking them up to each battery and having the switch in the off position? Thanks again for your time.

 

[tpenfield]

Off position will do . . . BTW, in most cases a general purpose marine battery will do for both batteries, verses a separate 'starting' and 'deep cycle' batteries, which as you can see complicates matters.

 

[bruceb58]

Yes, I realize it is not a "true" accessories only and engine only, it is more of a I am using this battery or this battery depending on the situation.

Then that switch is fine. I have one of my boats with a switch like that. I also have another where all house loads are completely on the separate battery. For most boats, its not worth the trouble to get all the accessory loads moved over.