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Powering an LED strip with a 12v battery

  1. Jun 10, 2017 #1
    Hi,

    I want to run a cheap 5 meter led strip along the inside of my boat for cool night lighting. It will be powered by a 12v deep cycle battery. I was hoping y'all could double check what I was thinking before I set something on fire...

    Here is the led strip https://www.amazon.com/gp/product/B00IZA2URS/ref=ox_sc_act_title_5?ie=UTF8&psc=1&smid=ATVPDKIKX0DER

    It says it uses 2 amps and 12 volts. One thing I'm curious about is if the led's will be affected by the fact that the 12v battery is actually about 13v when fully charged.

    I was planning on using 20 gauge wire from the positive electrode to a 5 amp fuse, to a switch, to the led strip, and then back to the negative electrode. Another thing I was wondering was if it is ok to have thin wires hooked up straight to the 12v battery.

    This is the switch if it matters. https://www.amazon.com/gp/product/B000MMFIZS/ref=ox_sc_act_title_1?ie=UTF8&psc=1&smid=ATVPDKIKX0DER

    Thanks,
    Terry
     
  2. jcsd
  3. Jun 10, 2017 #2

    berkeman

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    Staff: Mentor

    Sounds good to me so far, unlesss I've missed something. Post pictures of it working!
     
  4. Jun 10, 2017 #3
    Will do! Thank you!
     
  5. Jun 11, 2017 #4
    The circuit sounds fine. However, although 20 AWG easily handles the current, voltage drop and power loss may become a concern if it is through a long wire run. Resistance is for solid, uncoated copper wire at 20°C in this comparison. 20 AWG wire is 10.15 milliohms per foot, and 16 AWG is 4.016 milliohm/foot.

    For a 10 meter (32.8 foot) wire run, 20 AWG wire resistance is 0.33 ohm, drops about 0.69 volts, and dissipates about 1.3 watts for this 12V/2A load.

    If wire size is increased to 16 AWG, wire resistance falls to 0.13 ohm, voltage drop to 0.27 volts, and wire dissipation to 0.53 watts.
     
  6. Jun 11, 2017 #5

    jim hardy

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    2016 Award

    Two things

    1. Keep the run between battery and fuse short. That's so there's small likelihood of it getting pinched and shorting out in an unfused part of it.
    2. Be aware that if it does get short circuited upstream of the fuse it'll get very hot. If this is a fiberglass boat you don't want it to set the hull afire. So choose your routing with physical security of the wire in mind. Avoid the gas tank .

    Is there a fuse panel with a leftover space you can get power ? I'm accustomed to finding these in boats:
    http://www.overtons.com/modperl/pro...ang-Fuse-Block-Sierra-Part-FS40600-1&i=752205
    You might add a fuseblock . Success in adding your first gizmo is likely to inspire more.
     
  7. Jun 13, 2017 #6

    sophiecentaur

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    You really needn't worry. There are thousands (millions?) of LEDs used in cars and boats. Whilst the early Power LEDs may have been a bit sensitive to working conditions, they are pretty much Plug n Play these days. A charging 12V lead acid accumulator can measure 14V and LEDs can cope with that. They also 'work' on a flattish battery, just getting a bit dimmer. The cost of abusing even a deep cycle battery is far greater than what it can do to any of your lights.
    As for choice of wire gauge, reels of wire have a current rating marked on them. Stick to half that value and you are fine on a boat of just a few metres. Of course, thicker wire is stronger, physically and that's an advantage in many practical circs. Thin wires can easily come disconnected when disturbed. Corroded connectors will lose volts for you. Plated wire with solder - tinned ends is recommended by some marine enthusiasts for good connections and there are better connectors available than the ordinary 'chocolate block' styles.
    Any wiring from a battery should have a fuse that's comfortably less than the rated current for the wire. A car battery can melt almost any thickness of wire. There is no significance in connecting a thin wire directly to a battery. It's the total resistance of the current path that governs the current. It is important to locate the fuse close to the battery because the upstream length is not protected. There are so may ways that + and - terminals can get an unintended short circuit between them; a screw from the other side of a bulkhead or a heavy item squashing the pair together.
     
  8. Jun 18, 2017 #7
    1tR9fAjlDd5xx685GESIy1RH-w_01tucXinuhqsYM4zIAmabiMWCKquDpCGzYypLz-2M6dZjg25hmy45qcX-hcKnG8AjZZ4h.jpg
    Thank you everyone for your help. The finished product looks amazing!
     
  9. Jun 19, 2017 #8

    sophiecentaur

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    Very pretty! The only think you need to worry about now is draining the battery as you admire your results all evening with the engine not running. Do you operate the boat with two batteries? That usually takes care of the problem of starting the engine on a flat battery. :smile:
     
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