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  1. #1
    Join Date
    Jul 2001
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    Cyberspace
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    35,571

    Default Charging engine battery via 1-2-both switch

    .
    Both solar panel and battery charger are connected to the domestic bank only. Will switching to 'both' charge the engine start battery?

    (No lectures on the satanic nature of 1-2-both switches please, it exists)

    - W

  2. #2
    Join Date
    Dec 2012
    Location
    Fortrose
    Posts
    1,535

    Default Re: Charging engine battery via 1-2-both switch

    Yes. Easy to check with a DVM also.
    Folkboat 'Stakkr' - Inverness - http://islandrov.wix.com/island-rov-web

  3. #3
    Join Date
    Oct 2001
    Posts
    1,408

    Default Re: Charging engine battery via 1-2-both switch

    Yes.

    But I'd be worried about what happens if the domestic bank was knackered.

  4. #4
    Join Date
    Jul 2001
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    Cyberspace
    Posts
    35,571

    Default Re: Charging engine battery via 1-2-both switch

    Quote Originally Posted by James_Calvert View Post
    Yes.

    But I'd be worried about what happens if the domestic bank was knackered.
    I don't think it is, but what specifically would you worry about?

    - W

  5. #5
    Join Date
    Mar 2002
    Location
    Greenwich
    Posts
    7,446

    Default Re: Charging engine battery via 1-2-both switch

    If the domestic bank was knackered you could discharge the engine battery. I like 1:2:Both systems for anyone who doesn’t need to ask questions about using them. I always used the B when on board and charging so I could keep an eye but mostly just started with engine only - charged for 15 mins then through Both to Domestic and charged on that.

  6. #6
    Join Date
    Sep 2001
    Location
    Home - Sothampton, Boat - Gosport
    Posts
    10,071

    Default Re: Charging engine battery via 1-2-both switch

    Get yourself one of these

    https://www.sunstore.co.uk/product/e...er-12-24v-10a/

    It'll take care of both batteries while keeping them separate. I also use an el cheapo headlamp relay energised from the alternator charge warning light terminal as a split charge relay. You could do the lot for change from £50

    Yes, I know it isn't the most efficient of controllers, but it does the job unless you're desperate for the last milliamp hour of output.
    Steve
    Never believe anything until it has been officially denied.

  7. #7
    Join Date
    Dec 2012
    Location
    Fortrose
    Posts
    1,535

    Default Re: Charging engine battery via 1-2-both switch

    Quote Originally Posted by RupertW View Post
    I like 1:2:Both systems for anyone who doesn’t need to ask questions about using them.
    Exactly my view.
    Folkboat 'Stakkr' - Inverness - http://islandrov.wix.com/island-rov-web

  8. #8
    Join Date
    Apr 2018
    Location
    Mooring, Faro
    Posts
    1,566

    Default Re: Charging engine battery via 1-2-both switch

    Quote Originally Posted by webcraft View Post
    .
    Both solar panel and battery charger are connected to the domestic bank only. Will switching to 'both' charge the engine start battery?

    (No lectures on the satanic nature of 1-2-both switches please, it exists)

    - W
    Yes it will but, could be a problem if the solar regulator voltage is set too high for the engine battery. Our Trojans charge at 14.82 but the engine (car battery) is sealed so needs lower voltage.

  9. #9
    Join Date
    May 2016
    Location
    Suffolk
    Posts
    7,749

    Default Re: Charging engine battery via 1-2-both switch

    Quote Originally Posted by webcraft View Post
    .
    Both solar panel and battery charger are connected to the domestic bank only. Will switching to 'both' charge the engine start battery?

    (No lectures on the satanic nature of 1-2-both switches please, it exists)

    - W
    The single most significant reason 1-2-B switches are not as good as separate switches is the need to fiddle around to get the batteries charged up. Second most significant reason is owners using the switches incorrectly. This idea encompasses both of those points, as do some of the replies.

    All of the time the switch is in "Both" the batteries are in parallel and any issue that affects one battery affects them all. If a battery fails due to a shorted cell, for instance, that battery will get very hot and discharge any battery connected to it. So, if that happens while you have the switch set to both, you lose all power.

    "Not likely to happen" i hear someone saying. But i've seen it happen several times, twice on my own boats (luckily i had separate systems). I received an email from a customer just last week, an extract reads ;

    "
    Whilst under sail alone, a continuous high pitched alarm sounded after about half an hour of turning the engine off. We started the engine and the alarm went off. When we stopped the engine it was then that I noticed the voltage dropping fast on the BVM. The voltage level on the BVM was down to about 10.5v."

    That perfectly describes what happens. If that boat had been using a 1-2-B switch, set to both, the engine battery would also have been flat. Fortunately, the boat has separate switches and split charging.

    So, my advice, don't do it. Fit a VSR, i'd recommend the Victron Cyrix 120a. The advice to fit a headlamp relay is also bad advice, that's not better than using the "both" setting.
    Rainbow Marine.
    www.rainbowmarine.co.uk

  10. #10
    Join Date
    Jul 2001
    Location
    Cyberspace
    Posts
    35,571

    Default Re: Charging engine battery via 1-2-both switch

    .
    I never use the 'Both' switch. I charge the engine battery for 15 minutes after starting the engine then switch to the domestic bank. This is only to top the engine battery up prior to launch or in any other situation where it is inadvertently discharged.


    - W

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