Connecting two 12v batteries for longer run time?

  • Profile photo of walleye_wisdomwalleye_wisdom
    Participant
    Big Sky Country Helena, MT (Adel, IA home)
    Posts: 1,160
    #1237314

    I’ve got a 12v bow mount motor on my new boat. How do I connect two 12v deep cycle batteries together to gain more run time than if I was just running them off of one battery?

    Also, if one battery is weaker than the other, will it ruin the good battery? Thanks!

    Profile photo of walleyejoewalleyejoe
    Participant
    Litchfield, MN
    Posts: 431
    #766902

    I am not sure how to connect them but if you are going to do that your going to want to get two new batteries that match or one will cause harm to the other.

    avatartrumar
    Participant
    Rochester, Mn
    Posts: 5,352
    #766904

    Positive to positive and neg to neg ,both batteries should be should be of the same shape and size for best results

    avatarHot Runr Guy
    Participant
    Posts: 442
    #766908

    Make a pair of 8 gauge (or larger) jumpers, and connect the negative to negative, positive to positive. This is called a parallel connection, as opposed to the series connection if you want to create 24 volts from (2) 12 volt batteries. And yes, a weaker battery will draw a stronger one down.
    HRG

    Profile photo of bassn7bassn7
    Participant
    Bruce,WI
    Posts: 639
    #766952

    the biggest problem is when you charge 2 dissimilar batteries one will over charge or 1 will under charge because both batteries won’t take a different charge when hooked together.

    Profile photo of kootykooty
    Keymaster
    1 hour 15 mins to the Pond
    Posts: 16,519
    #767037

    You will want to create the parrallel connection mentioned above. I would also suggest charging them seperately, meaning disconnecting them during charging.

    avatarHot Runr Guy
    Participant
    Posts: 442
    #767054

    Part of the problem, like Kooty explains, is that the batteries should be “seperated” from each other when charging. Take a look at this mini battery selector switch. If you hooked-up your TM positive lead and your positive charger lead to the common post, than run leads from the switch to each battery, you could then charge each battery (1 at a time), yet set the switch to “both 1+2″ for the longer run time you’re looking for.
    HRG
    http://bluesea.com/category/1/products/6007

    avatarCzech
    Participant
    Cottage Grove, MN
    Posts: 1,577
    #767093

    Isn’t pos to pos 24v parallel? Did the poster say 12v? Wouldn’t that be pos to neg? No expert here, just checking.

    avatarHot Runr Guy
    Participant
    Posts: 442
    #767098

    Positive to positive (and negative to negative) is 12volts. Positive to negative (series connection) is 24volt.

    avatarCzech
    Participant
    Cottage Grove, MN
    Posts: 1,577
    #767108

    Thanks HRG! Now I know. I haven’t blown anything up yet. Did I say yet?

    avatarjon_jordan
    Participant
    St. Paul, Mn
    Posts: 10,928
    #767112

    If you spend the money on that switch, I’d set it up to run off one battery. Then when that one runs down, flip the switch to the fresh one. Charge up the same way.

    Also, if you do run the batts in parrelle, run you leads off ONE battery.

    -J.

    Profile photo of ajsajs
    Participant
    Mellen,WI
    Posts: 248
    #768546

    Battery size is not important if you use one bigger one smaller the smaller will charge faster yes but once its charged the bigger battery will continue to charge and the smaller will not also a battery tender will help prevent over charging both batteries the only reason i know this is. A im a mechanic and B ive ran several dual battery setups on my race trucks. But to each his own.

    Ajs

    Profile photo of ajsajs
    Participant
    Mellen,WI
    Posts: 248
    #768557

    Also as jon jordan said connecting both leads to one battery is the easiest. Heres a diagram of the proper wiring.And i forgot to mention if one battery is bad it will drain the good battery you can charge them and bring them to a shop or auto parts store and get them tested to see if they are good.

    Profile photo of ajsajs
    Participant
    Mellen,WI
    Posts: 248
    #768576

    Did both my posts get deleted??????????

    Profile photo of sliderfishnsliderfishn
    Participant
    Blaine, MN
    Posts: 5,117
    #768578

    I still see them, but the diagram you posted is gone.

    Profile photo of martin_vriezemartin_vrieze
    Participant
    Eagan
    Posts: 485
    #768652

    I had to do the same thing when I got my new boat…everything posted here is right on the money.

    Profile photo of ajsajs
    Participant
    Mellen,WI
    Posts: 248
    #768673

    I think my computer is having a bad hair day but here,s the diagram again.

    Profile photo of jkratkyjkratky
    Participant
    Lino Lakes, MN
    Posts: 170
    #771224

    when you have a 24v system, (trolling motor) can you still connect a 12v locator to ONE of the battery’s, with out blowing the thing up? the reason for the question is my 520c is connected to the fuse panel under the dash with the power coming from the starting battery, to much interferace when i.m running the boat motor. how else can i get away from the interferace, and connect to what. Also when going across the lake at higher speeds i lose the depth reading and it just starts flashing wrong depths, what can correct this? my trans seems to be positioned right.

    Profile photo of ajsajs
    Participant
    Mellen,WI
    Posts: 248
    #771225

    Locator should work fine as long as it hooked to only one battery and for the depth readings im pretty sure the locator cant keep up with your speed which is pretty common unless you have a high end locator.IM sure there is better terminology for this but im not up to date with it.

    Profile photo of jkratkyjkratky
    Participant
    Lino Lakes, MN
    Posts: 170
    #771227

    Thanks Andy, could i run an extra set of wires from the starting battery and connect directly to the locator without the interference problem will running the big motor? it’s an i/o merc. just thinking of all options and what makes sense with the less hassle but still getting? the BEST results?

    jk

    Profile photo of ajsajs
    Participant
    Mellen,WI
    Posts: 248
    #771326

    Try that it might fix your problem but im not sure i cant remember off the top of my head exactly what the problem is. One thing you can check is the plugs and wires on your i/o if they are not resistor wires and plugs it will cause interference when the motor is running. Mainly the wires would be at fault but the plugs may also cause this.

    Ajs

Viewing 21 posts - 1 through 21 (of 21 total)

You must be logged in to reply to this topic.