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Old 10-01-2011, 17:59   #1
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Connecting Two Batteries Together

Simple question I hope.

Is there a benefit of 1 way over the other as far as connecting 2 house batterys together in parallel, aside from additional cables?

a) 2 batteries connected directly with jumper cables and using a simple On/Off switch to disconnect from panel load
or
b) each of the 2 batteries connected to a 1/2/Both switch and the switch normally in the Both position. Gives abilty to disconnect 1 from the other, but that should never be needed under normal usage.


Batteries are next to each other and switch is within a foot of them, so distance is not an issue. Looking for pros/cons

Thanks
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Old 10-01-2011, 18:10   #2
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If they are both house batteries then I would connect them together with one feed to the switch. However, as they are already cabled up then I would run with the switch on both. If you ever need to do any re-cabling (such as adding another battery) you could then cable them all up together, if you wished.
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Old 10-01-2011, 19:30   #3
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I'm adding a 3rd battery. Currently have just 2 deepcycles that provide for both starting and house power. They are in parallel and don't allow for any safety starting if needed. Not the best setup for overnighting away from the marina. Figure now is time to provide for that, so cables and switches will be purchased once I get a game plan. Want to add a sep starting only for the 2 motors, and recable the 2 as dedicated house only. Of course a switch would allow for emergency combining.

Was not sure if there is a current gain to be had doing it 1 way over the other, beings the cables are short enough that voltage drop isn't an issue.
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Old 10-01-2011, 19:40   #4
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Use your two deep cycles for your house batteries and then buy the third battery as your start battery. Purchase a battery combiner or an isolator so you will not have to remember to turn any switches. Your start battery will never go dead this way.
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Old 10-01-2011, 19:45   #5
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I am not sure I completely understand the question.

Connecting the batteries in parallel (Positive to positive and negative to negative terms) increases Amp-hour capacity. For example, two (2) 50Ah batteries in parallel would provide you with 100Ah capacity. I see the need for parallel IF you have the need for drawing amps over a longer period of time.

I agree with DeepFrz, just connect them together on a single switch. I believe the three position switch just adds complexity - if your purpose is to increase capacity over time.

Hope this helps.

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Old 10-01-2011, 20:33   #6
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Quote:
Originally Posted by David M View Post
Use your two deep cycles for your house batteries and then buy the third battery as your start battery. Purchase a battery combiner or an isolator so you will not have to remember to turn any switches. Your start battery will never go dead this way.
Yes, this is exactly my plan, both starters to 1 starting battery. Also plan to use 1 motor to charge the starting battery, while using the 2nd motor to charge the house bank with a Blue Seas ACR between the start and the house bank. That allows for both motors to equally charge all 3 batterys.

My question was main if there would be a power loss by using the 1/2/All switch setup vs the simplier ON/Off config. I think not in this case (short cable lenghts) , but asking just in case I'm overlooking something.

I agree, the single on/off switch is more simple. I'm afraid I was trying to reengineer the wheel. I will still provide for a way to combine the batteries if need be, just didn't go into it here.

Thanks for the advise guys.
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