Do you need to Start with both batteries

[Catchem]

Just a question that I am not to sure about.I have a dual battery switch on my boat which goes from off to one or both batteries.Do I need to start my boat on one or both?Do both batteries charge at the same time when it is on both?I have done the search on this but still not sure of the answer.Sorry but this is my first boat with this kind of setup.Any help would be appreciated.It is a 6 cyl cobra OMC.

 

[Sea Six]

Re: Do you need to Start with both batteries

Are you sure your battery switch doesn't read OFF - 1 - BOTH - 2 ? You should start and run with battery 1, and use battery 2 for accessories while you are not running. Your alternator will charge both 1 and 2 while the switch is on 1. When you are docked and turn the switch OFF, you will still have power to your bilge pump and your radio memory (station presets).

 

[Catchem]

Re: Do you need to Start with both batteries

Sea Six.I will have to check that out,but i think your right.So start on 1 and use 2 for accessories when not running.Sounds reasonable.Should I buy a deep cycle for No#2 or would it make any difference?

 

[Sea Six]

Re: Do you need to Start with both batteries

I guess it depends on what kind of load you will draw. If just a radio or fish finder, may not matter. If running a trolling motor, then you might want a deep cycle as #2.

 

[Boatist]

Re: Do you need to Start with both batteries

I have to disagree, if your switch is wired the normal way and it is set to 1 then it will start off battery one and will charge only battery 1. Set to both it will use both batteries to start and charge both. Set to 2 it will start off of battery 2 and charge only battery 2. Now you can have a battery isolator or a battery combiner to charge both batteries with switch set to any position. One thing turning your switch to off or thru off with the motor running will normaly blow your alternator. Also if your switch is NOT a MAKE BEFORE BREAK then can blow alternator anytime you turn it with the engine running. How the radio and bildge pump work all depends on how the switched is wired. If they are wired to one of the batteries post on the switch then radio and blige pump will have power any time battery is charged. If radio and bilge pump is wired to common post or the starter/alternator post then if you turn the switch to off bildge pump and radio will also loose power.<br /><br />Battery one normaly is a starting battery. Battery 2 really depends on it use as sea six said. If you have a trolling motor then deep cycle is most likely what you want. Only thing is if you also want to be able to start your motor off battery 2 should your starting Battery die then you need a battery with enough Cold Cranking Amps to start your motor. With a 6 Cyl a group 27 deep cycle should work or you can get a combination Starting / deep cycle battery.

 

[Silvertip]

Re: Do you need to Start with both batteries

Boatist is correct. There are many ways to wire a battery switch. If a dual battery isolator is used, then Catchem's description is probably correct. The isolator allows charging both batteries regardless what the switch setting is. If the isolator is not used, then the batteries are simply two separate systems that can be connected together in the BOTH switch setting, or the load(s) connected to either battery. There are lots of wiring digrams available on line to show these two configurations. Do a search on "dual battery switch schematic"

 

[Catchem]

Re: Do you need to Start with both batteries

Thanks Guys.Think I will give this system a real close check and determine my needs and wire accordingly.Appreciate all the help.Some good advice here and now it gives me an idea of what to look for.Thanks again.