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Batteries in parallel - Can I double the CCA?-gctid341037

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    Batteries in parallel - Can I double the CCA?-gctid341037

    OK, so I need to replace my start battery but can't get the exact replacement here in Nassau. So I need a new plan!!

    The engine specs require a battery with 950 CCA with 160 minutes RC as a minimum.

    The best I can get here is 800 CCA with a RC of 120 min

    Not good enough!

    So, my thought is to buy 2 identical batteries and parallel them.

    My question is this: if I use the above mentioned battery specs (800CCA and 120A RC) and have 2 batteries in parallel does this mean I get 1600 CCA and 210 min RC?


    Yes, when you parallel two batteries you double everything but voltage. When you series two batteries you double only voltage.
    John Rupp
    1989 2455 Ciera Sunbridge
    5.8 OMC Cobra

    1989 3288
    Hino 135



      I do the same on my 3587 as they start both diesel engines.

      This way I get the most cranking amps that can fit my battery box.


        have you considered after you install the new batterys to visit the on board charger aspect .....or maybe you already have . the old chargers do not even come close to todays inventions ... take a look at for your size boat a 3 bank c 1240 or c1250 amp charger would fit the bill

        good luck

        p.s. i could have brought you 2 new battery a few weeks ago as we stoped on a ncl cruise in nassau ......haha
        NEIL S


          Is it just me? I hear the problems others have with starting batteries, size, etc. While I only have 150 Hinos, they're still diesels and draw a lot to start. However, I only have 1, group 27 battery that starts (one at a time) both engines. This battery has not been changed in 7 years. When I fire off the engines, they start so quickly that you can hardly hear the starter activate. So, I was wondering, do the Cummins and bigger Hinos draw that many more amps to start?

          "Safe Boating is No Accident"
          Everett Sail and Power Squadron


            No, I don't actually have any problems with my start batteries!! What I do have is insufficient house battery capacity. I was using an 8D for my start battery and another for house - this is how it came. But i found I was having to run my generator way too often at anchor.

            So I had a choice - increase house battery capacity by buying another 8D or paralleling my two 8Ds into a house bank and adding a new start bank. Here in Nassau, the simplest option was the latter which is what I did. And since my engines (Cummins 220's) need a minimum of 950 CCA I had to parallel two start batteries to give me some reserve as well.

            So, now I have about 450 amp-hours in my house and 2000 CCA for my start. Overkill? Maybe, but I don't want to run out of juice somewhere in a deserted anchorage in the Bahamas with the weather deteriorating! Now, hopefully I won't


              I use a single blue top optima to start both 250 HP hino's on my 3988. Works great. can alway jumper from gen set battery or cross-swith from house if needed. However, never have needed to in 4 years since the install. Get a smart charger!!!!


                Dinkytoy wrote:

                So, now I have about 450 amp-hours in my house and 2000 CCA for my start. Overkill?
                Actually, 450 AH for your house is still a little light considering you'll be anchoring out a lot. We have double that in our 4788. If you get a chance I'd increase your house bank.
                "Allante I" Rayburn 75
                Previous: '97 4788