Latest News: Forums Technical Portable power box

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  • #20886

    Hey guys –

    Ok, so this is verrry long, but just in case anyone is interested, I thought I would knock up a portable power box for long cruises.  – I wanted a way to charge the phone which has navionics installed for chart plotting, and I also have a clipper duet knocking around from an old boat, so I thought I should add that to for depth sounding areas unknown to me! I do have the speed paddle too, but dont see the need for extra cables at the moment.

    The transducer will clip to the transom initially, but it will probably soon end up siliconed onto the hull under the floor. The plug on the transducer cable fits through the compression gland on the box, so the cable can be unplugged and put in a waterproof bag out of the way when I am racing the boat, so that the box can be removed.

    The power box is compact (25cm across the front, 18cm front to back, and 15cm high), and will strap to a side bench wherever it is convenient.

    The battery is a 7ah rechargeable sealed lead acid, which has more than enough power for a weekend cruise, or longer. The depth sounder pulls less than 0.20ah, and the phone on charge pulls around 0.40ah.

    The meter to the left of the sounder pulls less than 0.10 ah, and is fantastic, as it gives readouts of current battery voltage, and a continuous rolling minimum and maximum amp draw.

    There are two (waterproof) switches installed in the system. The first turns the whole system on and off – and the second switch turns the depth sounder on and off independantly.

    There are two compression glands on the side of the box, one takes the transducer cable, and the second takes the speed paddle cable, in case I decide to use that too in the future. The second one is sealed off with a piece of solid rubber to keep it waterproof, for the time being.

    Just a note –

    on the opposite side of the box to the compression glands there are two 12v outlets. The top one is used for charging the phone, and running an all round white light on a long cable with a car adapter plug for night anchor.

    The second 12v outlet will be used if I decide to put a small 5w solar panel into the system. The 12v outlet will be wired to the solar panel regulator in the lid of the box, and then to the battery.

    Wiring it up like this means that the panel can be plugged straight into the 12v outlet (the panel has a 12v male plug on the end of its cord). This way, it’s possible to store the panel away from the box when not in use.

    Strictly, the panel probably wouldnt need a regulator, as the chance of overcharge is pretty minimal, bearing in mind the panel only gives half an amp an hour at its peak performance (in it’s first year!). Better to be safe than sorry!


    The box is just a temporary solution, and what I had laying around at the time. I also have a waterproof box which held a dumpy level, but didn’t want to hack holes into it until I am happy with positioning of everything!



    Battery – had one already, but £15 for a 7h version. (under a tenner for a charger)

    Box – whetever is to hand!

    Meter – £15 ebay.

    Compression glands – £2 ebay

    Phone holder – £5 ebay

    Waterproof switches under a tenner for the pair, ebay

    In line fuse – £2 ebay

    12v outlets £5 each, ebay

    Waterproof case for phone £20. (VHF version, as may fit charge cable into the aerial section of it)

    Clipper duet £150 new, though lots around second hand.



    The box used to check fit of everything:

     photo box6_zps7n5lztcn.jpg

    Switched on (both switches, running charging point and depth sounder:

     photo box8_zpstrduyeev.jpg

    Two 12v outlets to one side of the box – top one for charging, bottom one for solar panel input:

     photo box 2_zpsnbedwefq.jpg

    Compression glands on other side:

     photo box3 _zpsemal5y5b.jpg

    Inside box – also storage for transducer and front of mobile phone holder whilst not being used:

     photo box 5_zpsjgenh2xl.jpg

    Box with front of phone holder installed and phone in waterproof case:

     photo box bag_zps3fzhigzu.jpg

    Waterproof box for final install:

     photo box7_zpsb34vsqf4.jpg




    Here is my system, it worked fine for me for the last 20 years:

    Can’t See bottom: Its deep.
    Can See Bottom: It’s less deep than before.
    Centre Board comes up: It’s shallow.

    Skipper is bored and unhappy: Less than one knot.
    Skipper is sort of happy: We’re doing tree knots
    Skipper is smiling: 4 knots, almost planing
    Skipper is smiling and we’re hiked out: 5+ knots, planing
    Skipper makes weird shouting sounds and he has a smile from ear to ear: We’re in a 8 to 10 knot plane!

    By smell, tell tales, or where the rain hits our face. Ohw, and we use a Compass to trim the rain and the tell tales.

    Sound of water: We have not yet arrived at destination.
    Grinding sound: we have arrived at destination.
    BANG!  We hit the dock.




    Hahaha!!!..very good!

    I thought this post may go down like a sack of spuds, but I also thought what the heck, someone might find it useful! I only really designed the box for a long weekend cruise with the kids on board – and after getting my first sail of the year in last weekend, I was reminded how much fun it was to just go with it, and not worry too much. Too much winter time off to think of ways of making life easy when I am about to learn a new river – as they say, if it aint broke, dont fix it.

    The centreboard soon told us when we were coming past a shallow patch just before the slipway on our return to shore!


    i was thinking along similar lines to provide usb power for a navigation tablet (has all uk charts on) and mobile phone. It’ll be interesting to see how well the battery lasts over extended use & solar charging.

    Would a capsize in salty water short the 12v sockets?

    If it were mine i reckon i’d make the meter switchable so it’s not always draining the battery, overnight for example.

    i’ll let you know if i get my soldering iron out 🙂


    Hey – Once the kit is in the waterproof (yellow) box it should remain watertight during a capsize, but you are right, the 12v sockets may well suffer. I am planning on just using the box on cruises, and I hope not to capsize, but as we all know, there is always a chance! – short answer…I hope not to find out!

    The meter draws less than 0.10ah, but that does sound like a good plan – I may well add an internal in line power switch for it, for overnight use.



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