Battery Selector Switch ?

Discussion in 'Boating' started by catmankev, Feb 20, 2009.

  1. catmankev

    catmankev New Member

    Messages:
    442
    State:
    Valmeyer, Illinois
    I have a 12 volt trolling motor. I want to add a second battery for long days on the the water. Can anyone tell me how to connect a Battery Selector Switch? The switch I bought came with extremely vague instructions. Thanks in advance.
     
  2. Catfish_Commando

    Catfish_Commando TF Staff Member

    Messages:
    7,005
    State:
    Georgia
    I am wondering if you could just get over cheaper by connecting the batteries in parallel. We have some engineers that should chime in, "I Hope"...
     

  3. catman-j

    catman-j New Member

    Messages:
    1,020
    State:
    Eastern Nebr
    The proper name for the switch you would need is a single pole double throw (spdt) switch. You only need to switch between the positive posts on the 2 batteries, keeping the negatives grounded. I would look at bass pro or your local RV dealer. Click on this link at google and you should find what you want.
    http://www.google.com/search?q=mari...s=org.mozilla:en-US:official&client=firefox-a
    or google marine battery switches.
     
  4. catmankev

    catmankev New Member

    Messages:
    442
    State:
    Valmeyer, Illinois
    I already have the switch. It's a Blue Sea Systems Battery Selector Switch. I need to know how to install it.
     
  5. GaryF

    GaryF New Member

    Messages:
    3,649
    State:
    O.P., KS
    I just installed a Perko switch, not sure it's the same, but.... The switch has 3 posts, one goes to the positive on each battery, the third one is where your starter, trolling motor, and all boat wiring attaches. You will need to make 3 jumper cables, one to go from the positive post on each battery to the switch, and the 3rd jumper to connect the negative posts on each battery. Don't skimp on the cable and connectors for these jumpers, as you will probably need to use 4 or 6 gauge wire. I had trouble locating good 6 gauge connectors, eventually ordered them from Ebay.

    Things to watch out for..

    • Be absolutely sure that the cables to the switch can't possibly ground out on the boat or rub through the insulation. These heavy cables are unfused, and could do a lot of damage if shorted out.
    • You have limited space to work with inside the switch. If you have things like breakers or circuit interrupters you may have to get creative and add a junction box in which to make the connections. I had to do that. Use a heavy plastic box for this and be sure that there is no way anything can get grounded if stuff moves around in the box.
    • The Perko switch allows you to combine batteries, but that probably isn't a good idea unless they are fairly closely matched. One reason I did 2 batteries is to be sure that I always had one that could start the boat.. combine them and you might run down both. Also, if you cross connect a drained battery with a charged battery, the result could be that the low battery gets charged at an unsafe rate.
    • Beware of overworking your boats alternator trying to recharge a trolling motor battery. Most of these alternators are not made to operate all out for hour after hour to recharge a depleted battery on a regular basis. It's one thing to replace 5-10 amps used by the electronics and starter, it's another to replace 60-80 amps used by a trolling motor.
     
  6. Grimpuppy

    Grimpuppy New Member

    Messages:
    3,556
    State:
    Concordia, KS
    Are you using 2 trolling motor batteries and one starter battery for the big motor? If so, you don't need the switch. You can hook your trolling batteries in parallel. This is the way I have mine. But if you want the switch you can use it.
     
  7. GaryF

    GaryF New Member

    Messages:
    3,649
    State:
    O.P., KS
  8. catmankev

    catmankev New Member

    Messages:
    442
    State:
    Valmeyer, Illinois
    How do I connect my onboard charger to a parallel battery set up?
     
  9. Grimpuppy

    Grimpuppy New Member

    Messages:
    3,556
    State:
    Concordia, KS
    Preferably hook the charger to the first battery and hook the trolling motor to the second battery. If this is not possible it is OK to hook the charger to the same battery the trolling motor is hooked to. It is just preferred to separate the connections if you can. It takes a little longer to charge because you are doing 2 batteries instead of one. One thing I should point out is, both batteries should be the same brand and type. That way they discharge the same and charge the same.

    One other thing I have done is setup a quick connect between my starting battery and my trolling motor batteries. I used quick connectors like what tow trucks use on the front of their trucks to hook in jumper cables. One is hooked to my starting battery and one to my trolling batteries. Just in case my starting battery goes dead, I can connect it to my trolling batteries quick and easy and jump start myself. It is a lot better than carrying a big set of jumper cables around.
     

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  10. Fishlind

    Fishlind New Member

    Messages:
    11
    State:
    Lexington County, SC
    Have you got the switch wired yet, or are you still having problems?
    Joey
     
  11. catmankev

    catmankev New Member

    Messages:
    442
    State:
    Valmeyer, Illinois
    Haven't had a chance yet, maybe tomorrow night.
     
  12. mmarcum6

    mmarcum6 New Member

    Messages:
    599
    State:
    Tenneessee
    I will try and address as best I can with the limited knowledge of your exact configuration. First use good heavy wire for both the battery connections to the switch and the jumper that you will place between the negative terminals of the batteries. This will be the only common connection the batteries share other than the selector switch.
    Second you can take all the connections off the battery you currently use and connect all of them to the common terminal of the selector switch.
    Third connect the primary (starting battery) to the terminal labeled Batt 1 of the switch.
    fourth connect the second (trolling) battery to the terminal labeled batt 2 of the switch.

    fifth connect the negative terminals of the two batteries together and anything that is already connected to the negative terminal of your present battery leave it connected to the negative terminal of your present battery. Most of the electronics on the boat are low current consuming devices and it will not make a difference where they are connected. There will be one large wire connected to the negative terminal of this battery and it is very important it remains connected to the main battery. This is the negative wire for the starter of the big motor and it will be drawing its starting current from this cable. The smaller wires can be connected to either battery negative as needed as they carry much smaller currents and won't be effected either way.

    Now for the fun use the batt 1 position of the switch for starting your big motor. You can also run electronics in this position without a problem.
    Use Batt 2 position for the trolling motor battery and you can run your electronic in this position also without a problem.

    Don't start the big motor in the Batt 2 or both position unless it is an emergency as a trolling motor battery is not internally designed for this type of current draw and will degenerate the plates quickly which will limit their charge capacity quickly. Significantly reducing the life span of the battery.

    Don't run the trolling motor in Batt 1 position as this is the main cranking battery and the one you depend upon to get you back to the ramp or out of harms way quickly.

    The both position should be used in emergency cases say when for some reason the main cranking battery dies for no reason and you are ready to go home, and don't want to try and pull start a 100 hp motor. I will sacrifie a little deep cycle battery life to get home without pulling on a big hunk of outboard. In the emergency case switch the switch to Batt 2 crank the big motor and head for the ramp.

    I have but don't recomend running the switch in the both position as the trolling (deep cycle) battery will be charged to rapidly and this will do as much damage as discharging it to rapidly. I only did this on a long day of fishing when I was running between spots and took a chance of frying the alternator in the big motor just to gain a little fishing time. Dumb idea and I know better. I got a buy that time but may not get so lucky next time and don't advise trying it even once.

    If you have any questions PM me and I will answer as best I can. I'm an electrician and have one of the Perko switches in my center console. I start and run on Batt 1 and then switch to Batt 2 when I start using the trolling motor. I use an external charger and charge each battery seperatley. I plan on investing in a multi bank onboard in the next year, but will charge independently until then as different battery types have differently charging needs and rates.