'SHUNTS' - Electrical !!

Discussion in 'Tech/Mech General' started by davidallan, May 25, 2011.

  1. davidallan

    davidallan Funster

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    Its all to do with M/Home electrics.......Just read an article from an Australian website
    www.hobohome.com.....One of the pages deals with these devices [ a Lump of Brass] connected to the Battery [ it seems that some say on the NEG & others POS terminal:cry:]
    then ALL other wiring must be done from this SHUNT...None to the battery directly

    Interesting site with useful info--

    BUT have any 'Funsters' fitted such a device OR Have one fitted ??

    I for one can't really understand how they may 'Improve' the electrical system:Eeek:
     
  2. Gromett

    Gromett Funster

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    It doesn't 'improve' the system at all. It is there to cause an extremely small voltage drop that can be used to measure the amount of current flowing into the battery or out of it.

    You will mainly find them as part of monitors such as the NASA BM-1 and the Victron BMV 600.

    They serve no other purpose.

    Karl
     
  3. Geo

    Geo Trader - Funster

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    I have the BM1 device fitted with a shunt on the Neg
    I would say knowing exactly what is going in and out of your batteries was a big improvement
    It is important to have anything you want to measure using the shunt as the earth so that the BM1 sees it drawing current, if it is earthed elsewhere on the chassis it will not respond as accurately
    Geo
    PS the shunt is a little more than a lump of brass. it is a purpose built item
     
  4. wivvy's dad

    wivvy's dad Read Only Funster

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    That's a VERY interesting and informative website, that might even help an electrical numpty like myself to understand a bit better - thank you
     
  5. hilldweller

    hilldweller Funster Life Member

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    If you break the -ve to the battery ( which will go to earth/chassis ) then the BM1 will still read current even if using a chassis return.

    Measuring on the chassis side means that one of the sense cables is an electrical screen so picking up less interference.
     
  6. eddievanbitz

    eddievanbitz Trader - Funster

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    I agree that the knowledge of what is going on, and how many lights to turn out is invaluable.

    The entery level Nasa is great value for money but it will conflict with solar panels as it is designed for marine use where solar panels are not so common, but other than the solar panel glitch for about £80 you can measure every bit of power in and out of your battey and change your usage to reflect the amount of time you intend to stay

    Eddie
     
  7. Gromett

    Gromett Funster

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    I didn't know the Nasa unit wasn't suitable if you had solar panels? I am just about to fit a couple this weekend....... What does it do?

    The other thing with the NASA unit is that the % full fluctuates by 5% if you have anything that puts a slight load on such as a compressor fridge. This may be down to being too accurate. ie it updates the % full based on current usage over too short a time scale. The Victron version didn't do this and was much more usable although it does have a much smaller screen.

    This may not be an issue for most people but as I full time and rely on the batteries for my business I don't like the shock of seeing it drop down to 85% within a couple of hours of coming off hookup if I happen to look just after the fridge has switched off.

    I will be selling my Nasa unit shortly and going down the Victron route.

    Karl
     
  8. eddievanbitz

    eddievanbitz Trader - Funster

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    Having an interest in boats as well as campers I am always looking for products that crossover, that are usefull in both.

    When a solar panel in on the camper, the NASA will show the input to the batteries, even say in the winter when the panels are offering just a few milliamps. The trouble is the unit then ignores any discharge.

    This has the effect that once the sun goes down, the unit "catches" up and the display reflects this, making the user think that there has been a sudden discharge.

    This in itself is not a problem, once we realised that there was a conflict with solar we spoke to NASA Marine and we dissapointed that they knew about the problem, but didn't care enough to try to work out a resolution so we stopped selling them.

    There are loads of digital ampmeters available with shunts for a lot less than the NASA and loads a lot more expensive

    Eddie
     
  9. Gromett

    Gromett Funster

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    Damn, thats a major flaw for me.:-(
    The ones I have discovered so far such as the too accurate % tracking.
    And the 104% problem which they say just means it is fully charged.
    And the way the time left to dis/charge display goes whacky when it is working its way from 104% -> 100%
     
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