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  1. #41
    Join Date
    Aug 2011
    Location
    On the Celtic Fringe
    Posts
    12,078

    Default Re: General power arrangements - slightly disappointing

    I wonder if the original poster would benefit from reading a few books on boat electrics? Just a suggestion, he then might understand the advice offered.
    Cynical Scots engineer.

  2. #42
    Join Date
    Sep 2001
    Location
    Me - Zumerzet Boat - Wareham
    Posts
    11,102

    Default Re: General power arrangements - slightly disappointing

    Quote Originally Posted by Sandy View Post
    I wonder if the original poster would benefit from reading a few books on boat electrics? Just a suggestion, he then might understand the advice offered.
    A PDF of the 12v Handbook HERE. Their are also other sources.
    MontyMariner.co.uk
    Facilitated by AWESEM WP Agency

  3. #43
    Join Date
    Jun 2017
    Posts
    151

    Default Re: General power arrangements - slightly disappointing

    Quote Originally Posted by Sandy View Post
    I wonder if the original poster would benefit from reading a few books on boat electrics? Just a suggestion, he then might understand the advice offered.
    Indeed I would benefit from reading any number of books on all sorts of subjects!

    However sometimes it's easier to ask knowledgeable people for subject specific background info before going any further....

    I'm reasonably confident that my A levels in Maths Physics and Chemistry, old as they are, give me a basic understanding in AC & DC circuits and I spent far too many hours building engines in my youth giving me a grounding in vehicle electrics.

    My lack of knowledge, which perhaps I didn't explain well enough, was how, in general, small boats deal with the interface between the AC and DC systems and charging in particular. My knowledge about how smart chargers work is indeed lacking - I assumed that they sense or measure resistance and voltage across batteries and that switching in/out loads would muck that process up. My assumption appears to be wrong.

    As for my particular boat, my uncertainty is down to the fact that it is 40yrs old with the proverbial birds nest of wiring, some connected and some not. At this stage, and without serious examination, I gave no idea how the thing is wired up....prompting my post about what is 'normal' without having to read a number of books on the subject.

    Having said all that I appreciate the link to the 12v manual....some useful info in there esp. Around galvanic corrosion.
    Last edited by Sea-Fever; 27-02-18 at 09:59.

  4. #44
    Join Date
    May 2016
    Location
    Suffolk
    Posts
    5,675

    Default Re: General power arrangements - slightly disappointing

    The book does contain much useful information, but it should be remembered that it is 35 years old. Yes, ohms law hasn't changed, neither has a lot of other stuff in the book, but techniques and materials have changed. Still worth a read though.
    Rainbow Marine.
    www.rainbowmarine.co.uk

  5. #45
    Join Date
    May 2016
    Location
    Suffolk
    Posts
    5,675

    Default Re: General power arrangements - slightly disappointing

    Quote Originally Posted by Sea-Fever View Post
    My lack of knowledge, which perhaps I didn't explain well enough, was how, in general, small boats deal with the interface between the AC and DC systems and charging in particular. My knowledge about how smart chargers work is indeed lacking - I assumed that they sense or measure resistance and voltage across batteries and that switching in/out loads would muck that process up. My assumption appears to be wrong.
    My personal opinion is that you want as much 12v stuff as possible, but be able to keep up with demand when in a marina. If my boat is disconnected from the mains almost everything still works, without an inverter. I have to swap the 240v kettle for the gas one, the toaster and printer don't work and i can't charge the cordless power tools (i could rig DC-DC converters if i wanted, but no point), but everything else works. During the Summer the mains charger is off and the 12v systems run from the solar panels.

    During the Winter there isn't enough solar power, so i use the mains charger. I have a good quality 30a charger that can act as a power supply. When the batteries are charged is will keep them on a float charge, whilst still running varying loads. For instance, the battery monitor could be showing 0.2a going into the batteries to maintain them, whilst the charger could be outputting 4 amps, because i have some stuff turned on, if the fridge comes on the charger would be outputting 7 amps, but there will still only be 0.2a going to the batteries. If the batteries are being charged, the same applies, they batteries get what they need, whilst the charger output varies according to load.

    As for my particular boat, my uncertainty is down to the fact that it is 40yrs old with the proverbial birds nest of wiring, some connected and some not. At this stage, and without serious examination, I gave no idea how the thing is wired up....prompting my post about what is 'normal' without having to read a number of books on the subject.
    Sounds like a typical used boat. It's frightening what some owners consider acceptable when it comes to wiring. I usually start with correcting/modernising the battery/charging systems, hence my comments about the switching. Plenty of threads on here about that subject.
    Rainbow Marine.
    www.rainbowmarine.co.uk

  6. #46
    Join Date
    Jul 2002
    Location
    Home: Kent. Boat: Chichester
    Posts
    41,611

    Default Re: General power arrangements - slightly disappointing

    Quote Originally Posted by Sea-Fever View Post
    Indeed I would benefit from reading any number of books on all sorts of subjects!

    However sometimes it's easier to ask knowledgeable people for subject specific background info before going any further....

    I'm reasonably confident that my A levels in Maths Physics and Chemistry, old as they are, give me a basic understanding in AC & DC circuits and I spent far too many hours building engines in my youth giving me a grounding in vehicle electrics.

    My lack of knowledge, which perhaps I didn't explain well enough, was how, in general, small boats deal with the interface between the AC and DC systems and charging in particular. My knowledge about how smart chargers work is indeed lacking - I assumed that they sense or measure resistance and voltage across batteries and that switching in/out loads would muck that process up. My assumption appears to be wrong.

    As for my particular boat, my uncertainty is down to the fact that it is 40yrs old with the proverbial birds nest of wiring, some connected and some not. At this stage, and without serious examination, I gave no idea how the thing is wired up....prompting my post about what is 'normal' without having to read a number of books on the subject.


    Having said all that I appreciate the link to the 12v manual....some useful info in there esp. Around galvanic corrosion.
    There is a more recent edition (1998) of the 12 volt Doctor's book available , but not on line.

    You might also like to look at "Essential Boat Electrics" by Pat Manley. It's much more recent (2014) and British. https://www.amazon.co.uk/Essential-B...Boat+Electrics
    Last edited by VicS; 27-02-18 at 10:43.

  7. #47
    Join Date
    Nov 2009
    Location
    Southampton
    Posts
    34,057

    Default Re: General power arrangements - slightly disappointing

    Quote Originally Posted by PaulRainbow View Post
    My personal opinion is that you want as much 12v stuff as possible, but be able to keep up with demand when in a marina. If my boat is disconnected from the mains almost everything still works, without an inverter. I have to swap the 240v kettle for the gas one, the toaster and printer don't work and i can't charge the cordless power tools (i could rig DC-DC converters if i wanted, but no point), but everything else works.
    I agree; although I have a 240v system it only gets used when we visit a marina and then only when I can be bothered to get out the cable and plug in, which I frequently don't. The only time I consider it essential is when we'll be staying put for two nights, since without power that means using the kettle for hot water to wash up the second dinner .

    I have Makita's own 12v charger for the drill batteries.

    Pete

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