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My boat only came with one battery and I would like to install a second. I do have a battery switch. Just not sure where to go from here have heard of too many different ways to hook it all up. Any help would be great? Thanks
 

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If you have the standard "1 - Both - 2 - Off " type of battery switch - take the cable off of your current battery (pos. terminal)and put it on the switch " out or load" terminal. Put a new cable from the pos. of the old battery to either 1 or 2 "in" on the switch. Put a new cable from your new (additional ) battery pos. to the other "in" terminal of the switch (whichever terminal you didn't hook the old battery to). Run a new cable between the negative terminals of both batteries. If there is an "AF" terminal on the switch, and you want to use it, run the alternator charging wire to this terminal. (keeps from burning up the alt. if you turn the bats off with the engine running). If there were any wires running bilge pumps that stayed hot all of the time on the original battery, you should probably leave them hooked to one of the battery pos. terminals so they will operate with the new switch turned off, otherwise, once you turn the switch to the "off" position, everything will be dead. This is the standard. old time way to hook up 2 batteries - there are other methods, this is the simplest.
 

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Go to Perko.com and download the battery diagram for your set up.

When I installed a 2nd battery, I also installed a "bus bar" which is my common ground. All of my negative wires (from both batteries, electronics, engines, ignition) are screwed into this. (A bus bar has 4 screw terminals, so you can attach everything).

Then hook the positives from each battery to the corresponding switch terminals (#1 & #2) and run your ignition cable, engine +, and any electronics positives to the "All" switch terminal. Remember that your stereo, bilge pump, and possibly GPS need to be direct wired to a battery + terminal and not to the switch (b/c they need juice even if the switch is turned off).
 

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Here's something I did when I installed my second battery to make charging easier. It involves two modifications: one to the boat and one to the battery charger.

On the boat, install a Marinco battery charger inlet, available at West Marine part # 191991. This will allow you to plug in the female end of a standard 3-prong extension cord. Wire each spade connection (hot) to the positive terminal of each battery, and the ground connection to the common negative terminal of both batteries.

Make this box for your charger. Run the positive DC output of the charger to two switches, wiring the outlets to a female 110 volt outlet, one switch to each space connection. Run the negative DC output of the charger straight to the ground lug on the outlet.

Now you can leave your charger inside your garage, and connect it to your boat using an extension cord, and the switches allow you to charge just one or both batteries.

If you b-mail me with an e-mail address, I can send you a diagram.
 
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