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What battery do I need for these LED bulbs?

Discussion in 'LEDs and Optoelectronics' started by Matt Christensen, Mar 22, 2017.

  1. Matt Christensen

    Matt Christensen

    2
    0
    Mar 22, 2017
    Hi everyone,

    This is my first post, and I come to you all with a question about LEDs.

    I recently got some (10 pink, 10 red, 10 blue, 10 orange) from eBay, and I'm having trouble getting them to work. I'm wondering if I'm using too little voltage.

    The description said 9v-12v DC. So, I tried using a 9v battery, with some 9v battery connecters I got off of Amazon. I stripped the red and black on both the connector and lights (they were pre-wired), and connected everything, and got nothing.

    I went back to the listing page and found the chart that I've attached to this message. Does the chart mean I need to use a 12v power source instead?

    If that's the case, where can I go about getting one? I see Amazon has these A23 12v batteries - will those work? Or, do I need, like, a car battery or something? Are connectors available for A23 batteries as well? I didn't find anything after a quick search on Amazon.

    These LEDs are for a photoshoot on Saturday. So, I'm hoping to have a solution before then. If anyone knows more about this than me, and would be so kind as to reply, I would truly appreciate it.

    Hoping to hear from all of you!

    Thanks!
    -matt

    PS: Here is a link to the chart in case it didn't attach - https://app.box.com/s/nsp4e8pydhh8kxtj0tgyov2lmpx73fuh
     

    Attached Files:

  2. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    25,214
    2,695
    Jan 21, 2010
    It sounds like those are LEDs with a resistor wired in series with them so they will operate at between 9 and 12V at their nominal brightness (a very wide range by the way -- it suggests they are sticking any of resistor near the right value in there).

    The problem is that a reverse voltage as low as 7V can destroy a LED.

    The best test voltage is 5V. They should light up (perhaps dimly) if the correct polarity is applied, and not be damaged if the incorrect polarity is applied.

    If you go to our resource section the is a resource section on LEDs. The are a couple of ways to determine the correct polarity besides trial and error. Normally, looking for the longer lead is the easiest, but these likely have the legs clipped where the wires are connected, so the flattening on one side is probably the best option.

    If none of this helps then perhaps you could supply a photo of one of these parts so we don't have to guess what they look like.
     
  3. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    25,214
    2,695
    Jan 21, 2010
    And obviously one would normally expect red to be positive and black negative.

    And I assume you're checking one at a time, not dirt chasing them together (which won't work)
     
  4. Matt Christensen

    Matt Christensen

    2
    0
    Mar 22, 2017
    Hey,

    Thanks for the reply! I actually figured out a solution that should work, given that these lights will only be on for a matter of 10 minutes. I got some of the A23 batteries and just attached the wired leads to each of the poles with electrical tape. The lights (all four colors) lit right up. Since I'm not looking to build anything permanent, I think a Frankenstein-type setup like that will work great.

    Thank you again for your help! I'll definitely be back in the future if I have any more questions.

    Take care!

    -matt
     
  5. Audioguru

    Audioguru

    2,618
    593
    Sep 24, 2016
    The datasheet for an Energizer A23 alkaline battery shows that its duration is only a few minutes if you try to power 4 of those LEDs at the same time. Most of the battery power is heating the resistors attached to each one. You might even see the light slowly dimming.

    The A23 battery has eight tiny button cells in series. If you make your own battery with eight AAA or AA cells then it will last much longer.
     
  6. Herschel Peeler

    Herschel Peeler

    401
    65
    Feb 21, 2016
    It sounds like the 9 V battery could not supply enough current to drive the LED/ Tell us more about the LEDs.
    The chart may not apply to your LEDs.
    9 to 12 V? How much current?
     
  7. Audioguru

    Audioguru

    2,618
    593
    Sep 24, 2016
    An LED is a diode. It must be connected with a current-limiting device (usually a properly calculated resistor) and with the correct polarity.
    Maybe the LEDs from ebay are cheap Chinese fakes but a few of them might work.
    Please post a schematic of your test showing:
    1) Battery voltage, size and polarity
    2) LED color and polarity
    3) Current-limiting resistor value

    EDIT: Since the minimum voltage for the pre-wired LEDs is 9V then they must already have a current-limiting resistor or a few LEDs are connected in series so that they begin to light with 9V and are very bright with 12V. Did you measure the voltage from your battery, it might be lower than you think.
     
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