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Thread: Dual batteries

  1. #1
    Member AKBighorn's Avatar
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    Question Dual batteries

    It appears that I have added too many electric components to the boat based on one of the last runs I made. With the additon of the Depthfinder, lighted compass, VHF Radio, pot puller etc I killed the battery. I don't remember off hand what size the battery is that came in the boat but appearantly I need a dual battery setup. I am wondering if connecting the batteries parallel or with a switch is the best option. How are yours setup?

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    Member sayak's Avatar
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    Default Switch it!

    Use one of the red rotary switches that allow you to have left, right or both.

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    Member AKBighorn's Avatar
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    Default

    What are the benefits of the switch?

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    Default switch

    One reason to use a switch is safety, say you are out and for some reason you kill a battery you switch to the other one and you have a good battery, if you run both at the same time you have two dead ones.

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    Member TWB's Avatar
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    Default

    Main points are the ability to isolate the 2 batteries and also isolate them from any circuit on the boat, for instance if you gain a short or draw somewhere, you can close the circuit and not risk killing the battery'(s)
    We do not go to the green woods and crystal waters to rough it, we go to smooth it. We get it rough enough at home; in towns and cities; in shops, offices, stores, banks anywhere that we may be placed

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    Member Alaska Gray's Avatar
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    Default

    I have the red switch where I can go from Battery 1 to 2. Or I can run both at the same time. The switch is great If one battery is low I move the switch to both while driving my boat the charged battery will recharge the bad one.
    Living the Alaskan Dream
    Gary Keller
    Anchorage, AK

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    Default 12 volt systems

    I've had boats up to 38' requiring everything from simple to complicated house/start battery systems. The best guidance I've seen is by David Smead who wrote Living on 12 Volts and Wiring 12 Volts, both execellent books. His firm, Ample Power has a web site you can download sections for some ideas on how best to hook up your batteries for long life and reliable power:

    http://www.amplepower.com/primer/index.html

    The battery switch is a must to isolate manually at least so you always have start power as you run down your house bank when not charging. Adequate charging is also a must. An isolater can also be used but there are drawbacks described in Wiring 12 Volts so check it out.

    Good luck!

  8. #8
    Member AKBighorn's Avatar
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    Default

    Swithc it is. Thanks for all the info.

  9. #9

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    Spend some extra money on your new battery switch too. Make sure it's a 'make before break' version. Otherwise, you can fry your engine alternator when switching between batteries with the engine running.

    Fish witch...

    Good website, thanks for the link.

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    Member Crumm's Avatar
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    Quote Originally Posted by AKBighorn View Post
    With the addition of the Depthfinder, lighted compass, VHF Radio, pot puller etc I killed the battery.
    While dual battery's are great (I run two with a switch) it sounds to me like you also need to upgrade your alternator. While dual battery's will prolong things you will still kill both battery's if you are drawing more than you are putting out.

  11. #11
    Member AKBighorn's Avatar
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    Crumm, I was concerned with that as well especially with adding a stereo that might get alot of use. Having a sportjet in the boat I don't know if that is possible. I suppose I should look into that as well.

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    AKbighorn I am a trained auto tech and to test your charging system on a auto you put a load on the system lights on fan on high ect and run engine up to 2000 rpm it should charge at 14 volts or a bit better you could do somthing like that on your boat. Run the things you normally use when runniing the boat and make sure you are getting a good charge on your way to and from the fishing hole ect.

  13. #13

    Default Boat Battery

    Google "The Hull Truth" for battery info. Tons of info on there. If you go to two batteries and the red rotary switch be aware that your batteries will charge best if you only run one at a time. Reason is that they will only charge to the level of the weakest battery when running both at the same time. I run on one battery on the way out to the fishing hole and switch to the other one on the way back. I also buy good batteries. A dead battery could be more then a little problem in Alaskan waters.

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    If I remember correctly you're running the 175? The 175 only has a 12amp alternator. The 200, 240 and 250 have 60amp alternators. I wonder if one of them would be interchangeable with yours?

    I would reccomend a Perko brand switch.

  15. #15
    Member AKBighorn's Avatar
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    Quote Originally Posted by George D View Post
    AKbighorn I am a trained auto tech and to test your charging system on a auto you put a load on the system lights on fan on high ect and run engine up to 2000 rpm it should charge at 14 volts or a bit better you could do somthing like that on your boat. Run the things you normally use when runniing the boat and make sure you are getting a good charge on your way to and from the fishing hole ect.
    George, last year after killing the battery I had to pullstart the motor to get home. Fortunatly it was nice day with flat water or well..... Anyway, my depthfinder has a voltage meter on it and after having the problem with the battery I messed with the electronics on the boat. I had to pull my pots before returning and left the motor on since the battery was dead, that worked although may have been hard on the charging system. The thing I noticed was this little heater/blower that I installed to keep the windshield clear, well it ran most of the day, but anyway I noticed the voltage drop a few volts when I turned it on ( I beleive as low as 11v). I suspect it draws more juice than I would like. With the heater off, the system was charging as you described. I suspect that adding a battery for use mostly on the days when everything is on so to speak, will address the issue. When this happened we had gone out to Applegate, the weather was really foggy and it was cold out. Lights, heater, radios, etc. were all on all day. That was the last trip in the salt although the boat was used in fresh water a few times since with no problems. Any additional input is appreciated.

  16. #16
    Member AKBighorn's Avatar
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    Default

    That is correct FG, I have the 175. I'll have to look into your suggestion.

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    Yes if it is getting below 12 volts that is not good. Somethings to look at if you have made sure you are getting a good charge are... Testing the batteries after a load has be on them just because a battery shows 12.6 after being charged does not mean the battery recovers after a load has been put on it. Another thing to look at is making sure when everthing is off you are not having something drawing from the battery. If you find you need a new battery or are going to add the other one get a deep cycle battery. Also I would make sure you conections are very clean and something to keep that way. Hope this helps if you have more questions I will try to answer them.

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    I see I did not make something as clear I a should have, your battery is a storage so adding another battery will help you but not if it is also not receiving full charges; you need to make sure you are charging at 14 volts when running and better then 12 volts at idle or you will get a discharged battery sooner or later depending on your use ect. Up grading your charging system as talked about by others here is somthing you may need to do, unless your fan proves to be your major problem.

  19. #19

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    If you have the space, I recommend keeping on board one of those portable (~$70) batteries that have the jumper cables built in. They also have built in a compressor of sorts that can be used to air up tires in case you have problems on your trailer. I keep one on board. It adds weight and takes up some space, but it's always there in case I need it.

  20. #20
    Member mod elan's Avatar
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    skydiver- I second the 'jumper box" idea. I carry one in the boat every time. Have bought two over the years. Only about $50 at Sam's club if memory serves. Excellent suggestion!

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