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Thread: Backup battery

  1. #1
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    Default Backup battery

    I am planning to install a separate house battery on my 26' boat. I currently have one starting battery which has the necessary 800 CCA for starting the motor (225 hp Honda). I would prefer to have 2 batteries: 1 starting and 1 house.

    I have noticed many house batteries only have 600 CCA. Is this enough to start a 225 hp motor - at least to rely on as a backup? Probably a stupid question, but it's easier to ask than to purchase and install to find out.

    Thanks.

  2. #2

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    I've read that it's not a good idea to use the deep-cycle battery as a starting battery all the time because it's bad for it. I'd read that as also meaning that you can start your boat with your deep-cycle battery.

  3. #3
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    Default something to keep in mind

    An RV switch will isolate what ever battery you pick, but remember that the engine is only delivering a trickle charge , unless it is an up graded charging system.
    Personally I would add one of two things as well , a wind charger and or a solar pannel.
    also a switching system to monitor and control maintainance to the batterties, so that as one ages , it does not drain the other .

  4. #4
    Member breausaw's Avatar
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    Don’t use any switch unless its marine approved, like a Perko:

    http://www.overtons.com/modperl/product/details.cgi?i=31620&pdesc=Perko_Battery_Selector_S witch&aID=601S1C&merchID=4006


    Also, a deep cycle battery will work find as a cranking battery; it will not hurt it. I have two deep cycles on my boat and switch between them depending on the situation. I’ll run everything overnight on one battery and it will still start my main, and if for some reason it doesn’t the other battery will be fully charged.

    What you don’t want to do is run on both batteries at once, this won’t leave you a backup if you screw up and leave something on that drains the juice.

    I wouldn’t leave port without two fully charged batteries.
    Jay
    07 C-Dory 25 Cruiser
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  5. #5
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    Agree - I am planning to install Blue Seas Add A Battery (ACR) which will allow the house and starting battery to remain entirely separate, but will charge both batteries from a single source. Their webpage ishttp://bluesea.com/products/7650

    In this manner, I can keep both batteries separate unless under an emergency situation, I can then combine them for starting purposes. I currently have the standard Perko switch (off, 1, combine, 2), but this arrangement requires manual switching every time I want to use the windlass, electric pot puller, etc.

    I don't want to purchase a house battery that would not be able to start the motor on an infrequent (emergency) basis.

  6. #6
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    Arleigh:

    If I am not mistaken a 225 hp Honda alternator put out 60 amps, after you subtract what it take to run the engine, I would think it would be less than 10 amps that leaves 50 amps to charge a battery.

    Why would you say “but remember that the engine is only delivering a trickle charge”?

    Do you have difference information?

  7. #7

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    A yamaha 115 only puts out 25 amps at WOT and 150 35amps. I'm not sure about the honda 225. I had this discussion with Scan Marine down in Seattle and they told me about an Alaska State Trooper boat that was having electrical issues. Basically it ended up that with all the electronics, pullers, and heater the outboards didn't produce enough charge to keep the batteries topped off. I can't remember exactly what they did to fix the trooper boat. Scan Marine recommended topping off the batteries after each trip with a good charger. Now I carry a small honda generator on the boat with a small battery charger. (The battery charging feature on the generator is only about 2 amps) Having the generator with charger also eliminates the risk of an alternator going out and then killing my batteries.

  8. #8
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    Default The best batteries are the 6 volt deep cycle golf cart wired in series.

    I use these exclusively through out my solar and wind mill charging system.They tend to absorb a charge more readily and have a deeper capacity than 12 vollt batteries .As for boat applications and such I have a small 5 hp engine/ automotive alternator, that we used during the winter, when the sun was low on the horizon. The alternator can spin either direction and make power don't sweat it. Most any 5 hp gas engine will do . For the fuel invested this is the most effecient method of charging a battery bank system I know of (using mechanical means that is)

  9. #9
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    20 years of spending up to 2 weeks at a time fishing and living on my bowpicker and all i ever had was 2 Costco rv/marine deep cycle batteries running through a standard battery switch, never any problems.

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  10. #10

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    I use this set up.wiring.pngplus shore power, an AC panel and two battery chargers. I also carry a 2KW HONDA GENERATOR to plug into shore power if all else fails.

  11. #11
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    Default

    You've brought up a topic that will generate an unlimited number of options and ways to power your boat on batteries. Keep in mind your actual needs and how complicated you want to get. I suspect your 26 footer has minimal house needs and like Potbuilder says, a couple of cheap Costco batteries with marine selector switch is pretty simple and may be all you need as long as you are diligent in switching to only one battery while the engine is off. Bigger boats with more demand for DC power bring more complicated and sophisticated options to consider - you can really get carried away and turn this into an ongoing tweaking to get a system that meets your needs for staying out on the hook for extended periods. If all you're looking for is security to start in case of a drain at anchor, then get as big a battery as you can fit and remember to keep in mind that you may be affecting list so you might need to move it around to balance the boat right while setting still. The Costco marine deep cycle batteries are a decent choice btw, I have two and one starts my diesel just fine so an outboard should be OK. I do have an isolator so I don't have to worry about running on both to allow charging and switching to one when the engine is off for security. Good luck and keep it simple, you can tweak it later to fit your needs better as you go.

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