Highest Volatge advisable

Discussion in 'OnBoard Electronics & Controls' started by BertKu, Jun 21, 2012.

  1. BertKu
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    BertKu Senior Member

    Hi there,
    What do you feel is the highest Voltage, which one should use on an electric boat.
    36 Volt ?
    If one is half naked and touch the plus 48 Volt. The resistance of the body may be such that the current flow through your heart could be close to the 20 mA and that is a killer.
    What do you suggest.
    Bert
     
  2. gonzo
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    gonzo Senior Member

    If your installation is going to be bare and you operate the boat half naked, 12V is the safest.
     
  3. DCockey
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    DCockey Senior Member

    In the 1990's the auto industry devoted considerable resources to higher voltage electric systems for engine starting, lights and other accesories road vehicles. One of the major considerations in selecting the higher voltage should be was safety if a person while grounded contacted the hot side. The standard which was agreed to was 42 volts, 3 X the current standard. Before someone immediately responds with the current standard is 12 volts and 3 X 12 volts = 36 volts, not 42 volts let me explain. While the system in today's cars is almost universally refered to as a "12 volt" system, it actually operates at around 14 volts. 3 X 14 volts = 42 volts.

    Production electric propulsion systems in cars usually operate at considerably higher voltages, even several hundred volts, which can be hazardous if directly contacted. Such systems have extensive insulation and other features to prevent contact by humans when energized. Similar features would be needed for a boat propulsion system if voltage higher than "42 volts" is used.
     
  4. Submarine Tom

    Submarine Tom Previous Member

    I think Gonzo hit the nail on the head!

    I would use terminal fuses and 48 volts with every other safety measure possible.
     
  5. BertKu
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    BertKu Senior Member

    Agree with you, I have never seen dressed people on a boat, however one could safely have 24 or 36 Volt and convert this to 120 V AC 60 Hz. Possible double seal the terminals at the battery. I don't mind to get 120 AC shock but DC is a killer when too high.
     
  6. BertKu
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    BertKu Senior Member

    True, but it also means that the solar panels have to run at 4 x 15/16 Volt and will be in excess of 60/70 Volt to charge the batteries. That will be very tricky I think. O.K. one could with a very complex system charge each battery per solar panel, but still.
    Listening what you al have said, I stick to 24 Volt and have some thicker copper cables or insulated bars running.
    Thanks for your thoughts on this subject
     
  7. mydauphin
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    mydauphin Senior Member

    I have 96 volts leaving my solar panels. It is not voltage that kills but amperage. A stray 6 volts can kill you if you swin thru it.
     
  8. WestVanHan
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    WestVanHan Not a Senior Member

    Yes.

    I run an electric fence charger-5000 volts-to keep the bears (and anyone else) away from my cabin...I've had a few mishaps with it...still here.

    24 volts max IMO,finding equipment to run off higher voltages is very hard and pricey.
     
  9. MechaNik
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    MechaNik Senior Member

    I agree with West, you really have to have some strong reasoning to exceed 24v as it is not practical.
    As it is a marine environment you are not likely to take advantage of lighter wiring either using higher voltage. Do you want a boat wired with fragile cables that can mechanically fatigue and cant tolerate any corrosion before failing. I have big fingers and hate working with tiny things.
     
  10. CDK
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    CDK retired engineer

    Bert, where most boat owners have a sign to take your shoes off, you should have one that says "High Voltage! Wear Rubber Boots! Admittance only when fully dressed".
     
  11. BertKu
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    BertKu Senior Member

    You better don't touch the 96 Volt when the sun is shining and with your bare feet and hands. Your solarpanel is capable of supplying most likely more than 2 Ampere and that means sufficient current to flow through your body as parallel resistance to the terminal and to ship you to the graveyard. DC is nasty, as it makes your hand contract and you cannot let loose and the probability of getting more than 20 milliAmpere through your heart is great. You heart will not survive. I agree with you that even with 6 volt under certain circumstances could possible fatal.
    The reason why I ask this question in this thread, let say we have 20 KWh energy in the batteries, and for whatever reason I collect seawater, I have to protect myself. By 24 Volt, I should survive, I will measure my body resistance with bare feet in seawater and make my hands wet with seawater. Will let you know how may Ohms I have.
    Bert
     
  12. BertKu
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    BertKu Senior Member

    Except for the girls ...grin.
     
  13. BertKu
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    BertKu Senior Member

    Hi, you see, most brushless motors need 48 Volt to supply 8,5 KW. By 24 Volt I will archieve only 2 Kw, i.e. 400 N , this maybe not enough when doubled up with 2 motors to push the boat in the sea with waves and wind.
    Bert
     
  14. gonzo
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    gonzo Senior Member

    As an experiment, lick a 9V battery terminals.
     

  15. MechaNik
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    MechaNik Senior Member

    Sure you can do one circuit and isolate positive and negative supplys nicely. Even place the conductors in nice isolation trays and use high voltage insulated terminals in watertight boxes to minimize exposure etc. But the rest of it including the propulsion's control circuits are best kept to a more reasonable voltage.
     
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