20V Battery Powered LED Bar?

Discussion in 'Power Electronics' started by TL400EX, Sep 15, 2016.

  1. TL400EX

    Thread Starter New Member

    Sep 15, 2016
    3
    0
    Hey Guys,

    Obviously i am not an engineer... just a simple thinker. I would like to hook up a light bar to a walk behind leaf blower. It gets dark before i can get home and need maybe 30 minutes of light to work. I currently have Kobalt 20V cordless tools.... and thought it would be nice to use the cordless batteries to power the light, instead of having to hook up a normal battery. I currently have a work light, and with my 4ah 20V battery, it will last for hours. I know the led bar will drain it a lot quicker...

    I was thinking of buying the work light pictured below... taking off the current light and hooking up the wires to the led light bar. It would be an easy plug in for the battery and have an on/off switch. It sounds simple... but I'm sure its not. I don't know the specs on the work light. Here are the specs on the led bar. LED POWER:120W 12000LM(40pcs * 3W high intensity LEDs), Operating Voltage: 10-30 DC

    What will be my pitfalls? Thanks so much for your help, just trying to save time and money if it won't work.

    [​IMG]


    [​IMG]
     
  2. wayneh

    Expert

    Sep 9, 2010
    12,123
    3,047
    Well that sounds promising, that the LED bar can accept a range of input voltages. That means it has internal circuitry to provide a constant current to the LEDs as long as there is adequate input power.

    If it uses 120W, that means your battery (4Ah at 20V = 80Wh) will last only about 30 minutes. The amp-hour rating assumes a longer discharge time, maybe over 20 hours, and will be quite a bit lower at such a high current draw. That's an awfully fast discharge and may not be so good for the battery. Your photo shows a 2.0Ah battery.

    I'm not sure what your battery pack might have in the way of regulation. It's probably not just a battery with two wires. It might have a thermistor for temperature monitoring and it might have wires for balancing the individual cells during charging. It might take some research to figure out where the power leads are.
     
  3. Threeneurons

    New Member

    Jul 12, 2016
    19
    10
    Can you give us a link to the light bar in the lower photo ?

    The quick solution is to duct tape that light, in the upper photo, to your leaf blower, and the job is done. That's what Red Green would do, and I'm a big fan of Red Green :)

    I don't have any Kobalt tools, but I do have a new cordless drill, from its orange apron competitor. What I noticed about lithium ion powered tools, is when the power gets low, it just doesn't gradually weaken. Instead, it just stops. Full power for the duration, then dead off. I noticed this both with Ryobi, and when borrowing some fancier tools, from Makita and Porter Cable. If its lithium ion, its full power, then when its time for a recharge, they just shut off, abruptly. This is to protect the lithium ion batteries. There is protection circuitry added to the product to keep you from damaging the battery. Now, what I don't know, is if that circuitry is in the battery module, itself, or in the tool body. If its in the battery, then what you want to do is fine. If its in the tools, then I strongly recommend against it. Lithium ion batteries are nothing to screw with. If mishandled fire and explosions, are real possibilities.
     
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  4. TL400EX

    Thread Starter New Member

    Sep 15, 2016
    3
    0
    Well i decided to downsize on the LED since it would draw the battery so quick, i do have a 4ah battery (not shown)... here is the new led bar i found:

    https://www.amazon.com/gp/product/B01CV4AOOO/ref=ox_sc_act_title_1?ie=UTF8&psc=1&smid=A20J5QSSA04U8T

    LED power: 72W; 24pcs×3W high intensity CREE LED
    Voltage: 9-32 V
    Lumen : 7500LM

    I like that it already has the wires coming out of it... hopefully i could unhook the led panel that is currently on the work light, and just splice the led bar into the work light??
     
  5. wayneh

    Expert

    Sep 9, 2010
    12,123
    3,047
    I think so, but the devil is in the details. Does the current light connect with just two wires?
     
  6. TL400EX

    Thread Starter New Member

    Sep 15, 2016
    3
    0
    I took the top portion of the work light apart, the led panel is just a 2 wire hook up (blue + orange). Which one would be the positive?
     
  7. wayneh

    Expert

    Sep 9, 2010
    12,123
    3,047
    Do you have a multimeter? If not, consider a trip to Harbor Freight to get one free with a coupon. Use it to identify the proper polarity.

    Do you have a loose LED, a diode and a resistor handy? You'll want a resistor of least 1KΩ and a 10K would be better. If you have the parts, I can tell you how to use them to identify the polarity.

    It's possible you could identify the polarity by the reaction they have on your tongue. That's sort of a last resort approach. I suppose you could use an incandescent lightbulb and a compass also. I'd have to think about that one. And by think, I mean Google it.
     
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