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adding a second battery to my boat...suggestions on what to buy, sizes, kits etc

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  • adding a second battery to my boat...suggestions on what to buy, sizes, kits etc

    hello,
    i have a 20 foot GW invader bow rider with a 4.3 merc in/out. first boat so I've learned a lot over the past season. we managed to kill the battery once during the season just listening to the radio when it was tied to our dock, luckily we weren't out in the middle of the lake! I'd like to add a second battery to help run accessories and give me a little more piece of mind. the only accessories we currently have is the radio, i doubt we would ever add anything more then a depth finder to help navigate...piece of mind is also worth something to me. the current battery is a walleye mar 600 (manufactured by crown battery) it has the following info on the tag:
    MCA 625
    CCA 500
    RC minutes 75
    I've read that it's beneficial to have one battery to run accessories and one for starting, question is, is the battery i have good for either? if it will do ok with starting/running acc what should i add as a second battery? in addition to that how should i go about adding a second battery? i know there are kits available are some better then others? is it possible to buy some kind of switch and wire it up myself?

    any other comments? thanks so much for taking the time to read!!

    andy


  • #2
    Re: adding a second battery to my boat...suggestions on what to buy, sizes, kits etc

    Unless you have a high power stereo, and/or ran it for an exceptionally long time, that shouldn't have run a "good", fully charged battery down. So, there might be some things you want to check-out/verify, before changing your system. Autobilge pump stuck on, etc. Do you charge the battery regularly, after use? Do you have shore power, or power at your trailered site for a charger?

    While usually, an alternator can keep up with a good starting battery, once you add the second one, a charger will be required.

    Anyway, you will probably be good with just a basic DC battery for house, on a switch that allows for either/or both.

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    • #3
      Re: adding a second battery to my boat...suggestions on what to buy, sizes, kits etc

      i don't have anything special for a stereo, 4 speakers and the radio. my boat is on a lift and doesn't have power out to it. i could pull the battery after use and charge if needed i suppose. if i added a deep cycle as a second for example you are saying that i would need to manually charge that battery periodically as the alt would not charge the second battery during use? the one dead battery situation we had the boat hadn't been used in a few weeks and a light may have been left on also...i'm just looking to provide myself with a little piece of mind and avoid going to use the boat and not being able to because i have a dead battery. am i going down the wrong road?

      Comment



      • #4
        Re: adding a second battery to my boat...suggestions on what to buy, sizes, kits etc

        Originally posted by andy9743 View Post
        i don't have anything special for a stereo, 4 speakers and the radio. my boat is on a lift and doesn't have power out to it. i could pull the battery after use and charge if needed i suppose. if i added a deep cycle as a second for example you are saying that i would need to manually charge that battery periodically as the alt would not charge the second battery during use?

        You don't sound like you have much of a load. Theoretically, you could keep both batteries charged from the alternator. You would have to switch to the house to charge it. If you are running the battery down, while it is in the lift, and don't charge it back up, the life span of the battery will be greatly reduced. That to me, seems like the real issue.


        the one dead battery situation we had the boat hadn't been used in a few weeks and a light may have been left on also...i'm just looking to provide myself with a little piece of mind and avoid going to use the boat and not being able to because i have a dead battery. am i going down the wrong road?
        Having a 2nd battery, but not keeping tabs on it, can provide "false" piece of mind. It can be just as dead as your primary, when you need it. If you are hanging out in some cove all day, listening to tunes, etc, the batteries might have a chance to recharge on the trip back. But, if it is mostly at your dock, then some form of shore power might be the better approach. or just a battery boom box.

        Comment



        • #5
          Re: adding a second battery to my boat...suggestions on what to buy, sizes, kits etc

          Batteries are like buckets of electricity. whatever you use must be replaced or you find yourself on the business end of a paddle or waving a rescue me flag. During normal operation the alternator on the engine is perfectly capable of keeping the "starting" battery topped off only if you use accessories sparingly. Remember -- a short trip back to the lift will not top off charge a deeply discharged battery so some other means is required to do that. Not having shore power at the lift complicates matters. Adding a second battery is certainly a good idea for safety but it does not solve the problem of having either or both batteries dead at some point because there is no way to ensure they are topped off. While the alternator charges as long as the engine is running, it does not output much current at idle so only a prolonged run at moderate speeds will keep things topped off. You also have more accessories than you claim. You have lights, bilge pump, instruments, and the engine itself requires power to run. What charge the batteries get from the alternator is the difference between what is being "used" by the accessories and what is being "output" by the alternator. In your case, you don't need two batteries IF you had one large "dual purpose". For emergency use you could carry a smaller battery (like your current starting battery) that you keep charged at home. Install a battery disconnect switch to disconnect the battery from the electrical system. When you arrive at the boat there is no danger of having a dead starting battery because you forgot to turn something off. Your investment is the cost of a new, larger starting battery and the cost of the switch. Unless you make very long high speed runs, any other configuration -- such as a dual battery switch or ACR will likely be of little benefit. And before you ask -- solar panels are not the answer unless you install a large one on your lift and doing so will make it a target for theft unless the lift is in a secure area.

          Comment



          • #6
            Re: adding a second battery to my boat...suggestions on what to buy, sizes, kits etc

            All of the above has been excellent advice. I would also ask how old is your battery? Here in South Florida, 2 years is about it for a battery? Also, how much time do you generally put on the engines when you go out, especially on the way to your anchorage? Running time equals charging time.

            If you want a second battery, the first suggestion is that you put a standard cycle battery as the starting battery (provides lots of cranking power but doesn' usually get drawn down very far) and put a deep cycle battery (made for draining way down often) for the house (accessories).

            If you add a charging system, your charging source (engines or shore power) will get distributed to both batteries. With a charging system, all batteries should be of the same type (lead acid versus gel). Don't mix them.

            Switches - you can have one per battery (if you have one, just add a second) or you can put in a switch that has one, the other, or both. Its possible your current switch has both but the feature is not being used. Check it.

            Good luck...
            iboats: You Can Do It. We can help!

            Regards,
            Kick Back

            Building The Boat That No One Makes

            The "81 Sea Ray 26 Sedan Bridge I/O to OB Conversion/Restore (Pics)
            " Thread

            http://forums.iboats.com/showthread.php?t=520100

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            • #7
              Re: adding a second battery to my boat...suggestions on what to buy, sizes, kits etc

              Your boat/setup/use sounds similiar to mine. Check into this type of setup.

              I went with:
              Batt #1 - engine starting and bilge pump only.
              Batt #2 - electronics, finder, radio, 2 amps, 4 spkrs, sub woofer.
              Blue Seas ACR 7610 isolator/combiner.

              Simple setup, no switches, transparent operation, etc. I dry stack my boat and use it 3-4 times a month. With the above battery setup, everything stayed charged/recharged just fine. I tested the batteries several times through the season and the batteries were minimal 90% charged.

              Only thing I would change is to add a better starting battery (today group 24, next season group 27) and then an inexpensive battery charge level visual indicator (for peace of mind before I head out on the lake).

              Comment



              • #8
                Re: adding a second battery to my boat...suggestions on what to buy, sizes, kits etc

                Originally posted by Silvertip View Post
                Batteries are like buckets of electricity. whatever you use must be replaced or you find yourself on the business end of a paddle or waving a rescue me flag. During normal operation the alternator on the engine is perfectly capable of keeping the "starting" battery topped off only if you use accessories sparingly. Remember -- a short trip back to the lift will not top off charge a deeply discharged battery so some other means is required to do that. Not having shore power at the lift complicates matters. Adding a second battery is certainly a good idea for safety but it does not solve the problem of having either or both batteries dead at some point because there is no way to ensure they are topped off. While the alternator charges as long as the engine is running, it does not output much current at idle so only a prolonged run at moderate speeds will keep things topped off. You also have more accessories than you claim. You have lights, bilge pump, instruments, and the engine itself requires power to run. What charge the batteries get from the alternator is the difference between what is being "used" by the accessories and what is being "output" by the alternator. In your case, you don't need two batteries IF you had one large "dual purpose". For emergency use you could carry a smaller battery (like your current starting battery) that you keep charged at home. Install a battery disconnect switch to disconnect the battery from the electrical system. When you arrive at the boat there is no danger of having a dead starting battery because you forgot to turn something off. Your investment is the cost of a new, larger starting battery and the cost of the switch. Unless you make very long high speed runs, any other configuration -- such as a dual battery switch or ACR will likely be of little benefit. And before you ask -- solar panels are not the answer unless you install a large one on your lift and doing so will make it a target for theft unless the lift is in a secure area.

                this seems to make sense to me. the battery i have is a year old but i could keep it in the cabin as a back up on a trickle charger...the boat is used solely on a 600 acre inland lake for watersports 20-60 min at a time at varied rpm's. it is docked right in front of our cabin on a lift. adding a main disconnect also would be a great addition. what would be a good dual purpose battery? I'm assuming that the one i currently have is to small. what kind of specs should i be looking for? thanks fro the replies

                andy

                Comment



                • #9
                  Re: adding a second battery to my boat...suggestions on what to buy, sizes, kits etc

                  would an optima d27m or d31m be acceptable choices? they are stated to be good dual purpose batteries?
                  d27m
                  cca 800
                  mca 1000

                  d31m
                  cca 900
                  mca 1125

                  Comment



                  • #10
                    Re: adding a second battery to my boat...suggestions on what to buy, sizes, kits etc

                    If your lift is sitting in front of your cabin, why not just run an extension cord down to the lift each evening. Installing an on-board charger solves the problem of keeping the battery(ies) topped off. On a 600 acre lack you can paddle back so you are making much to do about nothing. Batteries have a label on them. Bigger numbers mean more capacity. Look for AHr (amp hours), RC (reserve capacity) which is expressed in minutes @ 23 or 25 amp load, or MCA (marine cranking amps). Group size is the physical size of the battery. 24, 27, 29, 31 etc. The bigger the box, the more power you can cram into it. Batteries are made by just a few manufacturers these dsays so paying more does not necessarily get you a better battery. Check your local farm and discount stores.

                    Comment

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