 | Home > In Car Electronics > Confirming current draw for light bars. |
 
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| Iain Member Since: 09 Nov 2014 Location: Aberdeenshire Posts: 79   
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Please could I ask for some help before I make up more of my loom for my roof rack light bars, beacon and work light?
I have 2 x 10 Duplex LED bars from Wilderness lighting being supplied from my standard 12v system on my MY2015 Defender via a blue sea aux fuse box. From wilderness website: "10 inch Duplex double row light bar, 20 x 5 watt OSLON white LED chips - 100 watts, Massive 5,600 LM of light produced while drawing only 4.1 Amps." They are wired in series so should be 200w of light coming from the single circuit which P=IV suggests would be 16.6A. I know I should have phoned them, but its now late on a Friday night and doubt I'll get a response until Monday. But yes I have gone and made up a loom for the 8.2A of the pair, with a significant safety factor thankfully. I test fired them this evening and they work brilliantly with the supply coming through a 10A blade fuse. (before I thought of this) Am I missing something, or has my safety factor in the wiring just been eaten up? How can they claim 4.1A draw, unless its in reference to an industrial 24v circuit? No fancy LED beats P=IV, does it? Thanks for any help so I can use the weekend to either continue or consider tearing it apart and replacing those wires? COTAG 4x4 Response 2015 XS USW Corris Grey on DF MTR's |
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7th Aug 2015 11:36pm |
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| munch90 Member Since: 26 Oct 2013 Location: guildford Posts: 3558 
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Might be worth buying a amp meter to check before fitting
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8th Aug 2015 5:19am |
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| LR90XS2011 Member Since: 05 Apr 2011 Location: bickenhill Posts: 3645 
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I expect you are correct and they are quoting the 24v current draw and as Munch says best to measure the current to be sure. Noted you said wired in series should they not be wired in Parallel rather than series? DEFENDER 90 TDCI XS,
I hope everyone is well and your land rovers make you happy |
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8th Aug 2015 5:25am |
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| K9F Member Since: 12 Nov 2009 Location: Bournemouth Posts: 9610 
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What you need to consider is the resistive load of the circuit: For example R=V/I and then factor that and compare to your formula of P=VI once you have figured out the current from the resistance value.
Your two lightbars are wired in series nevertheless how are the LEDs wired internally in each light bar? I suspect for the confusion that exists one explanation may be that the LEDs may themselves be individually wired in series which will increase the resistive value of the total circuit thereby reducing current draw. The drawback of this is that if one LED fails they may all fail? Bit like certain Christmas tree lights. Or as stated the current draw for a single light is based on a 24 volt configuration and your sums are correct and you will indeed be pulling 16 amps after all. If so replicate the loom you have made and wire each up individually to a common switch. As Munch states either a clamp meter, or a multimeter in series set to amps (you can do this across the removed fuse terminals if the multimeter is fused itself) this will tell you straight away what the current draw actually is or simply measure the resitance of each lightbar to be sure and use I=V/R.  If you go through life with your head in the sand....all people will see is an ar5e!!
Treat every day as if it is your last....one day you will be right!! |
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8th Aug 2015 5:33am |
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| Iain Member Since: 09 Nov 2014 Location: Aberdeenshire Posts: 79
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Thank you folks. Will check the actual draw today.
Also, the bars are in parallel, my late night error. Just the loom splits on the rack, hence majority of wire carrying load for both lights. COTAG 4x4 Response 2015 XS USW Corris Grey on DF MTR's |
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8th Aug 2015 7:33am |
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| Iain Member Since: 09 Nov 2014 Location: Aberdeenshire Posts: 79
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Just incase the info is of any use to others.
My elcheapo multi meter wouldn't give me a reading on Resistance or Amps in use. Got in touch with wilderness lighting who assured me verbally and in writing that regardless of voltage supply each light would draw only 4.1 amps, as per the website info. 9-36v supplies, all draw 4.1 amps. The physics of how, I don't know. My wiring is 17.5A rated, the weak link being the superseal connector with a 14A limit on each of the blade connectors. 10A blade fuse for the circuit. Thanks again to a great forum and its contributors. COTAG 4x4 Response 2015 XS USW Corris Grey on DF MTR's |
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11th Aug 2015 7:57pm |
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| K9F Member Since: 12 Nov 2009 Location: Bournemouth Posts: 9610
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It must be voltage regulation ensuring irrespective of varying input voltage supply to the leds remains the same.
If you go through life with your head in the sand....all people will see is an ar5e!!
Treat every day as if it is your last....one day you will be right!! |
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11th Aug 2015 8:16pm |
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