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Thread: Looking for the best way to add a battery to my boat

  1. #1
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    Default Looking for the best way to add a battery to my boat

    I am looking to add a second battery to my boat. The plan is to have one battery for the motor and kicker, and a second to run the downrigger, fish finder, electric motor, ect. I am considering using a Blue Sea "Add a Battery" Automatic Charging Relay to charge both batteries while the motors are running but isolate them when the motors are not in use. I was wondering if any of you have had experience with this system. Is it easy to set up? Is it better than a simple switch between the batteries? My concern is if I go with the simple switch, my second battery could drain my starter battery if I forget to change the manual switch. Thanks for the help.
    Sawtooth

  2. #2
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    Default

    I have not heard of the "Blue Sea" but most use a Perko switch that allows use of battery "A", battery "B" or both. It is a very simple system to use.
    2006 Dodge Ram 3500 Dually, 21' North River Seahawk

  3. #3
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    Is it possible that a run down or faulty House battery could run down your motors starter battery if the switch is left in the "both" battery position? In other words, does the the current run in both directions on the perko switch?
    I would like to charge both batteries when my motor is running, but I don't want to forget to turn the switch and drain my starter down to where it won't start the motor when I need it to.

  4. #4

    Default K.i.s.s.

    Personally, I would run the main and kicker motor on one battery, then isolate the other battery for the rest of the boat. Reasoning that you can simply attach both motors to one battery without any isolation and either would always charge that battery and then pass the rest of the amperage through the isolator to the other battery.

    You might get electronic "noise" on the fish finder if you decide to run it with the trolling motor, depends on how good the finder is. They normally draw very little current, which in my case I run my finder and GPS through the main battery.

    Regarding the battery, you should get as large as possible, dry (Optima type) deep cycle battery, the constant "cycling" or draining of a normal lead acid battery will kill that battery in fairly short order. I use two dry batteries from a forklift, they weigh close to 80lbs each for my trolling motor. Also make sure you put a charger on the second battery set-up every time you finish, because the main motor alternator will not likely fully charge it in the time back to the dock.

    http://www.napaonline.com/Search/Det...769_0006398311

    This has been used in motorhomes for years without fail. All you need in a simple battery isolator, the version I've attached from NAPA is rated up to 95 amps, which, unless you have a abnormally large alternator, would work fine.

    Make sure you use at least 6 ga. cable, preferably 4 ga., do not skimp on the cable, otherwise you will increase resistance which can lead to heating the cable to the point of melting. If you're going to balance the boat and place the battery forward, make sure to grommet any holes, regardless if this is an aluminum or glass boat, the vibration will eventually wear through the cable sheathing. Get good COPPER eyes, that can be crimped AND soldered, after crimping the cable correctly, take a propane torch and heat the ring end to wick the solder all the way into the base, as opposed to heating the cable and opening of the ring that is visible. No special tools needed for crimping, just a good dull drift punch and a vise.

  5. #5
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    sawtooth, the perko has a "both" position specifically for charging both batteries. It also has an off position so that none of the batteries are active while you are in storage.
    2006 Dodge Ram 3500 Dually, 21' North River Seahawk

  6. #6
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    Quote Originally Posted by SuperD View Post
    sawtooth, the perko has a "both" position specifically for charging both batteries. It also has an off position so that none of the batteries are active while you are in storage.
    I have the 'Perko' and agree with SuperD. From what I have seen its one of the most popular isolators that is used. There are others out there but they come with a price.
    2000 F250 7.3L Diesel
    2007 Columbia 2018 Fisherman XL Yamaha F150 Yamaha 9.9 kicker 4 Walker Electric Downriggers Raymarine Element HV 9 Uniden Solara VHF

  7. #7
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    Default

    Quote Originally Posted by sawtooth View Post
    Is it possible that a run down or faulty House battery could run down your motors starter battery if the switch is left in the "both" battery position? In other words, does the the current run in both directions on the perko switch?
    I would like to charge both batteries when my motor is running, but I don't want to forget to turn the switch and drain my starter down to where it won't start the motor when I need it to.


    Sawtooth,
    It sounds as though you want a perfect solution in an imperfect world. What you're asking can be done but not without some effort and or expense on your behalf. Electricity does flow both ways through the perko so yes, in answer to your question, one bad or weak battery could destroy the other. You could use a diode system in line in order to allow electricity to only flow in one direction but then you wouldn't be able to push a charge back into the batteries because of these diodes. The best way I can think of to accomplish what you are asking for, and the way I would do it myself, is to incorporate a relay mechanism powered by your motor's alternator/magneto that would make or break electrical contact with the charging system. If installed correctly, this would cause the second battery to only engage in the system when the motor was running and would disconnect it when the motor was shut off. I know of no better way to do this but you are creating some problems in regards to points of weakness to corrosion and failure in general in an otherwise pretty hardy system. And because I know of no one who manufactures such a system for boats, I think you may find it would be a bit cobblesome. I too have had occassion of memory failure and I can easily see where your concerns lie. But before I went to these extreme's, because I fear that they may cause you more trouble than they will help, I would try and memorize a list of "to-do's" for my boat operation. You have to pretty much do this when you load your boat on a trailer, things like making sure that your light connections are still good, make sure the winch is tight and the safety is connected well, and set the hold down straps. Kids have to learn this sort of thing when they begin driving, adjust your seat, adjust your rear view mirror, adjust your side mirrors, apply the seat belt. Just simply train yourself a "system" of shut down when you bring your boat in. You probably already have a system already established such as doing something with the key instead of leaving it in the ignition. All you need to do is add shutting off the perko switch to this list and then train yourself to do this out of habit instead of memory.

    In short, what you are asking for can be done but may or may not be worth it to you. The simple and I think best solution is to follow the good advice others have given in their suggestion of a perko switch because it is a proven device and not some experimental prototype combination. Not the answer you were looking for, I know, but a working solution none the same.

  8. #8
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    Sawtooth, on second thought, there is another way to do it. You could incorporate a system into your ignition switch and supply power to charge your battery this way. Still a lot of work and not sure it is worth it but, it is another way to get the job done. It just depends on how involved you want to get. It's not really the labor that is as involved as the thinking required to do this without creating problems in the process. I still think that training yourself a to-do list is an easier way, and a better way too. Best wishes to you however you decide to go on this, and happy fishing!

  9. #9
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    Skookum9,
    I understand the importance of having a routine when setting up and packing up my boat. But with two kids and their friends in the boat even the best made plans can change. I spend most of my time unhooking fish and untangling knots. :) But that's the price you pay to keep the fishing tradition alive.
    After reading your first post, it sounds like the relay you mentioned is just like the automatic charging relay I am asking about in my first post. I am not totally sold on any one system, but this ACR and Switch from Blue Sea got some good reviews in a couple of articles I have read on other boating websites. One article mentioned the downside of the manual switch I described above. I am just looking for feedback from others who have had some experience with this product to help me make my choice on the best system.
    I definitely don't want to make this more difficult then it should be, but if can protect my starting battery automatically and still charge both batteries when I am running my motor, that would be a bonus. I noticed that you are an electrician so any info you can share regarding this system would be appreciated.
    Sawtooth

  10. #10

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    Sawtooth
    I am here in Boise also, a mechanic by trade and while there are "custom" ways to design some special system, why? The manufacturers of battery isolators for motorhomes have been doing it for years without any issues. Almost all battery isolators are mounted under the hood of the vehicle, so they clearly designed it to be in the elements. Saltwater on the other hand is a bit harder on the aluminum casing, etc. but if you were going to sea with the boat, just spray a little WD-40 on it before you hit the water, problem solved.

  11. #11
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    I agree that if you have a system identified that is made for this purpose, it's worth a try. I am a regular high voltage and a low voltage electrician but that doesn't mean I know what is out there for boats and autos. If you try it and like, be sure to let others know because you would not be the only one with this problem. I don't like the WD-40 idea since over time WD increases corrosion. I do not know why WD does this but I have heard it and later found it to be true. Initially, WD does protect from moisture, but over time there must be some sort of breakdown that occurs and it actually draws moisture into the surface and actually accelerates rust. I can't tell you the how and the why, I can only say that I no longer use it as a rust/corrosion prohibitor. There are silicone sprays that will help though that I would recommend. They are made for protection from the elements.

  12. #12
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    Innnsxt,
    I certainly do not want to try and design a custom system. I am looking for an easy to set up, dependable, pre-made system. One that has simple directions for installation.
    Skookum9
    I will be taking the boat to the salt on occasion. This summer to B.C. for salmon, and maybe the jaws at Tillimook Bay in the fall if any salmon make it that far down the coast this year.:: I guess the fact that I will be in the salt is one of the reasons I like the idea of an Automatic Charging Relay. If I was only going to be fishing in the lakes here in Idaho, I can always swallow my pride and ask a fellow boater to give me a tow back to the dock. But if your motor won't start in the jaws at Tillamook or in a strong current in the straits between Vancouver Island and the mainland, you could be in a heap of trouble before help can arrive. Thanks to both of you for the idea of spraying my system with a corrosion prohibitor before heading to the salt.
    I have some silicone spray that is recommended for marine use that I will use.

  13. #13

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    Here is a good link. I think NAPA has the 95 amp unit for $35.

    http://www.surepower.com/pdf/isolator1.pdf

    The Blue Sea 7610 for example is just a plastic encased version of a isolator with an LED. After looking at this unit, the plastic would not help in the dissipation of the heat it could and usually does produce.

    As far as the rust scenario goes, almost the entire isolator is aluminum, with the circuitry encased in epoxy.

    I've never heard of a rust acceleration issue with WD-40, not that it isn't possible though. Silicone spray is a good choice as well, you can also spray the window channels of you car windows if they are getting slow going up.

  14. #14
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    Innnsxt, you are correct that aluminum does not rust, but it does corrode. I think they call that oxidization. For this reason all aluminum conductors must be treated with a protectant prior to installation, even inside a dwelling. If, on the other hand, the unit is anodized, this becomes a very moot point.

  15. #15
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    Default blue sea

    I have used and installed the blue sea systems in many boats. they are a plastic housing. If you use dielectric grease on the terminals or liquid neopreme on them you will have no corrsion. all my work has been in a salt water inviroment.
    your batteries will both be charged and there is no draw down from one to the other.

  16. #16
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    Here is a short video that best shows how to do it.
    http://www.youtube.com/watch?v=9YLvVP9ZPP4
    Whenever I feel blue, I start breathing again

  17. #17
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    Quote Originally Posted by skookum9 View Post
    Innnsxt, you are correct that aluminum does not rust, but it does corrode. I think they call that oxidization. For this reason all aluminum conductors must be treated with a protectant prior to installation, even inside a dwelling. If, on the other hand, the unit is anodized, this becomes a very moot point.
    Corrosion happens in most metals. What we call "rust" usually refers to what happens when steel corrodes, appearing "rusty orange". Aluminum corrosion appears white typically.
    Age 65.
    20 ft. Jetcraft. 90hp Evinrude Etec, 8hp Yamaha kicker, Minn Kota electric troller. Electric 1106 Scotty downriggers, Lowrance HDS7 Fish Finder/GPS. Airmar P66.
    Also have a 15 ft. Gregor. 25hp Yamaha electric 2-stroke. Two electric 1106 Scotty downriggers. Lowrance HDS7 Fish Finder/GPS.

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