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    #1

    Battery questions

    I know there has been a number of posts on batteries etc, but I have a specific question. I have two batteries, one is a deep cell (67AH) and another is a Interstate Marine battery, 500CCA. I have a Merc-cruiser 351, so I am assuming its a 70Amp alternator.

    I've done the math to figure out that the deep cell battery is plenty for the stereo system I'm putting in so here is my question.

    When buying an isolator, will a 70amp version be fine, or should I go up 1 level? If I do are there any downsides aside from the extra cost?

    Second, from some of the posts I've read regarding chargers. I am pretty sure that a 40amp charger is a bit more than I need, but is a 20 amp still too much?

    I am FAR from an expert when it comes to amps and ohms etc, so please forgive my ignorance.
    Reality is only an illusion that occurs due to a lack of alcohol.
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    #2
    Originally posted by jleger98 View Post
    I know there has been a number of posts on batteries etc, but I have a specific question. I have two batteries, one is a deep cell (67AH) and another is a Interstate Marine battery, 500CCA. I have a Merc-cruiser 351, so I am assuming its a 70Amp alternator.

    I've done the math to figure out that the deep cell battery is plenty for the stereo system I'm putting in so here is my question.

    When buying an isolator, will a 70amp version be fine, or should I go up 1 level? If I do are there any downsides aside from the extra cost?

    Second, from some of the posts I've read regarding chargers. I am pretty sure that a 40amp charger is a bit more than I need, but is a 20 amp still too much?

    I am FAR from an expert when it comes to amps and ohms etc, so please forgive my ignorance.
    I would look at a higher rated Iso so if you decided to upgrade the stereo/charging sys. you wont need to buy a new one.

    With a fairly stock set up, a 10amp would charge those batts overnight but a 20amp would be great too if you upgraded later.

    For longer "anchor time", I might suggest a higher Ah deepcycle. Just a thought.
    Mikes Liquid Audio: Knowledge Experience Customer Service you can trust-KICKER WetSounds ACME props FlyHigh Custom Ballast Clarion LiquidLumens LEDs Roswell Wave Deflector And More

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      #3
      I've got my system - and yes its modest - pegged at 55AH total over 8 hours, so I'm not too concerned at this point. If I have trouble, then yes, I'll upgrade. Rarely do I get a chance (with two younger girls) to be out on the water for 8 hours. Now...when I add the extra sub and tower speakers, then I'll have some issues, but this should do for now.
      Reality is only an illusion that occurs due to a lack of alcohol.

      Comment

        #4
        Originally posted by jleger98 View Post
        I've got my system - and yes its modest - pegged at 55AH total over 8 hours, so I'm not too concerned at this point. If I have trouble, then yes, I'll upgrade. Rarely do I get a chance (with two younger girls) to be out on the water for 8 hours. Now...when I add the extra sub and tower speakers, then I'll have some issues, but this should do for now.
        Double check the tag on your alt, some of the older ones have significantly smaller alts. Example; my 95' has a Mercruiser 350 and a 55 amp alt and I will be upgrading to a 100 amp unit from DB Eletrics.
        "Call me anything you want ... Just don't call me NOBODY!

        Comment

          #5
          Good idea, thanks! Maybe I'll go see "her" this weekend. 30 miles one-way though
          Reality is only an illusion that occurs due to a lack of alcohol.

          Comment

            #6
            Originally posted by jleger98 View Post
            I've got my system - and yes its modest - pegged at 55AH total over 8 hours, so I'm not too concerned at this point. If I have trouble, then yes, I'll upgrade. Rarely do I get a chance (with two younger girls) to be out on the water for 8 hours. Now...when I add the extra sub and tower speakers, then I'll have some issues, but this should do for now.
            If my math is right, 55 amp load on a 67Ah battery will give you 1.2 hrs of run time.
            Is your 55amp @ full volume? if so, figues it a 1/2 and your up to about 2.5 hrs.
            To go 8 hrs @ 55amps, you will need over 400Ah of RC
            Mikes Liquid Audio: Knowledge Experience Customer Service you can trust-KICKER WetSounds ACME props FlyHigh Custom Ballast Clarion LiquidLumens LEDs Roswell Wave Deflector And More

            Comment

              #7
              Current (A) = Square Root of (wattage(P) / resistance in Ohms(R))
              Sub Amp - 442W peak @ 2ohms - mono: sqrt(442) / 2 = 10.5 amps
              Main Amp - 170W peak @ 2ohms - per channel: sqrt(170 / 2) = 6.5 amps
              HU - 22W peak @ 2 ohms - per channel: sqrt(22 / 2) = 2.4 amps
              (I'm not running all at 2 ohms, but using that seems to be more conservative)
              Then - Total amps * hours * 40% - 19.4*8*.4 = 62.08 Amp hours
              Reality is only an illusion that occurs due to a lack of alcohol.

              Comment

                #8
                Originally posted by jleger98 View Post
                Current (A) = Square Root of (wattage(P) / resistance in Ohms(R))
                Sub Amp - 442W peak @ 2ohms - mono: sqrt(442) / 2 = 10.5 amps
                Main Amp - 170W peak @ 2ohms - per channel: sqrt(170 / 2) = 6.5 amps
                HU - 22W peak @ 2 ohms - per channel: sqrt(22 / 2) = 2.4 amps
                (I'm not running all at 2 ohms, but using that seems to be more conservative)
                Then - Total amps * hours * 40% - 19.4*8*.4 = 62.08 Amp hours
                I got ya now, I thought you were saying that your "modest" sys was drawing 55 amps I'd hate to see "all out"

                I concur: 19A max @ 40% continous for 8 hrs........your battery will be ok.
                Mikes Liquid Audio: Knowledge Experience Customer Service you can trust-KICKER WetSounds ACME props FlyHigh Custom Ballast Clarion LiquidLumens LEDs Roswell Wave Deflector And More

                Comment

                  #9
                  That might be enough power for the whole lake
                  Reality is only an illusion that occurs due to a lack of alcohol.

                  Comment

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