Underwater, battery-powered lights

Discussion in 'General Electronics Chat' started by Andrew Scarborough, Nov 23, 2014.

  1. Andrew Scarborough

    Thread Starter New Member

    Nov 23, 2014
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    I'm interested in using lights and a battery on a stand up paddleboard (SUP) for seeing into the water at night, as opposed to lights for navigation. The lights themselves would be under water and the battery would be strapped to the top of the paddleboard. Not too complicated. My concern though is what happens if the board flips over and the battery is submerged? Would there be a shock? For the sake of this question, let's say I'm using a 12 volt marine battery. In reality I wouldn't want anything that big and heavy, but if that was deemed safe then a 6volt lawn mower battery would be safe too. I like worst case planning.

    It seems like when a car crashes into a river or lake, either the people get out ok or they drown. I don't recall hearing about people being electrocuted, though I guess electrocution could lead to drowning.

    Anyway, my goal is to be safe. Thanks for any help!
     
  2. DNA Robotics

    Member

    Jun 13, 2014
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    I’m not sure much would happen in fresh water, but in salt water, electrolysis will dissolve the positive battery terminal and any exposed wire. I would put the battery in a water proof enclosure and seal where the wires come out with liquid electric tape or silicone glue.
    IF there were any shock hazards, that would eliminate them.
     
  3. Andrew Scarborough

    Thread Starter New Member

    Nov 23, 2014
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    Thanks for the prompt response. I think putting the battery in a waterproof container is a great idea. However I'm reluctant to rely on a waterproof container alone to protect myself and others. I like to always have at least one more layer of protection between myself and disaster.

    I guess the heart of my question was, would a big battery like a 12 volt deep cycle marine battery falling in the water shock any body in the water?
     
  4. profbuxton

    Member

    Feb 21, 2014
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    Chances of being shocked are extremely rare and I believe of minimal risk. Waterproof box is fine,but be aware of possible gases built up from battery on charge and discharge.
     
  5. sdowney717

    Member

    Jul 18, 2012
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    No, it would only conduct through seawater across its own terminals if it went in the water.
    Maybe if your hand was in the electron stream you will feel it!

    You can test with a couple wires, salt water and a guinea pig subject.

    Another test is use a hot dog, salt water and ammeter and see if any current flows through the hot dog. Hot dog would be used as a probe. One bare wire on positive, hot dog on negative. See how close they have to get to see any dangerous current flow. Both wire and probe sitting in salt water.
     
    Last edited: Nov 23, 2014
  6. ErnieM

    AAC Fanatic!

    Apr 24, 2011
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    There is no shock hazard from 12 VDC.

    I would be worried about leaking electrolyte once the battery hits the water. Even if it sinks to the bottom you have a minor environmental disaster lurking there. So a sealed cell (manufactured that way) is a must. Also secure it to the board with the expectation the board will invert.
     
  7. tcmtech

    Well-Known Member

    Nov 4, 2013
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    I would look into buying a divers flashlight or similar uni.

    They are designed to be underwater and typically have superior underwater beam characteristics.
     
  8. sirch2

    Well-Known Member

    Jan 21, 2013
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    I second tcmtech's advice. Salt water is horribly corrosive and generally only things designed for such an environment will last
     
  9. Andrew Scarborough

    Thread Starter New Member

    Nov 23, 2014
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    Wow! Thanks to everyone who took the time to respond. A lot of very useful advice. I came to the right place. Thanks!
     
  10. strantor

    AAC Fanatic!

    Oct 3, 2010
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    I've done plenty of similar experiments in the course of testing the conductivity of water, testing for optimal paramaters for electrolysis/electro-etching, and also a bit of testing directly on-topic: finding the preferred current path through water to determine the possibility of being electrocuted from standing in "energized" water.

    What I found is that trying to predict the magnitude and path of current through water is like trying to predict any woman's reaction to any bad news. Every woman is (slightly) different, and every bad news is different. The same woman's reaction to the same bad news may even vary greatly from one day to the next. If a team of scientists were devoted to developing a model of it, I doubt they would be able to tell us much more than "current flows through water, and the more impurities, the more current, ... usually" but I could be wrong.

    Current through water can do unpredictable things, for example there are confirmed cases of people being electrocuted by walking into flooded basesments where the water level was up to the wall outlets. Tell me why current would flow out from the L side of the plug, out across the room, up through a man's leg, through his heart, and down and out the other leg (or same leg), to ground, when it had a perfectly viable COPPER return path half an inch way.

    In any case, my point is that I dont think cute experiments with a hot dog in a glass of water are going to tell us much, if anything. At least not anything repeatable. That being said, in the case of a 12v battery, my gut instinct is that swimming with a 12v battery poses little threat - enough faith that if payed a handsome sum to do so, I would hesitate only slightly to carry one into the surf pressed against my chest. But in any other scenario I would take great care to insulate a battery from the water. I have seen a 12V battery pass upwards of an amp through salted tap water; more than enough to be lethal, but that is the sum of all parallel current paths in 3D space - not likely that all 200mA would go though your heart if you were between the probes.
     
  11. WBahn

    Moderator

    Mar 31, 2012
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    Consider that you can put your hands directly across the terminals of a 12V battery and, provided you don't have any cuts to pierce the skin resistance, you will feel nothing even if you press hard and your skin is damp. Putting everything into water is not going to increase the current flowing through you above that.
     
  12. BR-549

    Well-Known Member

    Sep 22, 2013
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    Low voltage battery lights should pose no danger......seal battery to protect water.

    Not to prove my point, but to example strantor's point..........

    About 20 years ago I went to work and the basement pump room was flooded a little over waist deep. I needed to open a gate valve in that room and was told the power had be cut. This was in the south and he water was warm so I waded across the room to open valve.

    As I was opening the valve....two submerged 480 motors kicked on. Thankfully the straight hair on my neck was due to fear, not charge.

    Since then I have seen many 480 motors run underwater.

    I chalk it up to good motor connection box handy work. And good wire insulation.

    However....I do not recommend this practice.
     
  13. strantor

    AAC Fanatic!

    Oct 3, 2010
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    Ok when summer comes back around, go outside and work yourself up a good dripping sweat and then go lay your arm across your car's battery terminals and rest your weight on it; like you would do if you were reaching far back to the rear of the engine compartment, and see if you feel something then. I agree, I've never been shocked by 12v between the hands, but the resistance of the palm skin is higher than elsewhere. I have never tried the above, but I recall reading on this forum others who said that they have, and did experience a shock. Would not be surprised either way if a shock resulted or did not, or if 100 people did the same test and some got a shock and some didn't.

    But if you were/had been swimming for a bit, and your skin was nice and saturated with salt water, I think there is a real possibility that you could be conductive enough to get a discernable shock; probably (probably) not an electrocution, but at least a shock.
     
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  14. sdowney717

    Member

    Jul 18, 2012
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    That is true
    If though you cut yourself in two places, and put a wire in each cut and attached to the 12v battery posts, then you would be shocked, maybe fried.
    Skin though is a good barrier. I have felt 12v tingles. And it is penetrating but very small burn like sensation constant not like AC. I forget but hands were wet with salt water and I may have had cuts- sore spot where the skin resistance broken down, and I was doing something with the battery posts.
     
  15. Geowizard

    New Member

    Nov 30, 2014
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    I can't recall having ever heard of anyone getting electrocuted by a 12 volt battery. :)

    There are other safety issues with an installation that may be prone to "upset" and possible short circuiting.

    1. The battery should be a sealed, gel-cell type and depending on the load, should be sized accordingly.

    2. A tilt switch should be incorporated that shuts down (removes the load) if an upset occurs.

    3. Standard marine spec. insulated terminals, connectors, fuse protection, wiring should be used.

    Batteries on this scale have been used in marine applications for years. It's a "mature science".

    Good luck!
     
  16. BR-549

    Well-Known Member

    Sep 22, 2013
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    What about all those Rambo movies?
    You know, where they got the hero strapped to a vertical bed springs?
    And they got the jumper cables with the car battery?
    And they always spark the cables before they connect them?

    And since then........all the other shows............I think I've seen Jack Bower more than once with jumper cables.
     
  17. Brownout

    Well-Known Member

    Jan 10, 2012
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    I sometimes use a 12v deep cycle battery in my canoe. There is no shock hazzard, but your battery might not survive. In most places, it's against the law to not have the battery strapped down so that it stays with the vessel. Waterproofing is a great idea.
     
  18. WBahn

    Moderator

    Mar 31, 2012
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    Oh, well since it was in a movie it must be true.
     
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