Nodge68
Well-Known Member
Absolutely. I was looking to import LED bars a few years ago, and had many samples sent from various Chinese factories for analysis (I'm a hobbyist electronics engineer). So I pulled apart many light bars, looking for decent quality candidates to sell on. What I found was, all these bars are modular in design, using the same aluminium extrusion, two types of reflectors (focused and diffused) with different length lexon glass, all using LED modules containing 6 LED emitters. Different types of LED emitters fitted, depending on how cheap the factory wanted to make them. The LED emitter boards also contain the LED driver circuit, which is matched with the LED emitters fitted, so to maximise light output.
The best (budget) bars I had sent were fitted with Cree XB-D 2.45mm X 2.45mm emitters. These emitters have a maximum rating of 3 Watts, and a light output of around 400 Lumens, but are normally under-driven to maintain a decent life.
Here's a pretty standard 2,400Lm 18 Watt, 6 X 3 W CREE XB-D LED module, which are used in multiples of to make up many different total wattage bars, simply by adding more modules in longer bars.
Cheaper made bars don't use CREE emitters, but normally low cost off the shelf 3 Watt LEDs (known to the Chinese as beads), which give only moderate lumen numbers (150 to 300Lm per 3W emitter),
Very expensive LED bars use premium LED emitters, often from CREE like the XL-G3 or Luxeon V2 with suitable driver circuits to maximise light output, and generally offering 30 Watts and almost 5000Lm per 6 emitter module. These high powered LED bars are really expensive, but offer the maximum light output in a standard length bar extrusion.
Nodge68
Well-Known Member
A decent 6 emitter light bar could well offer 3,500 Lm.
brianp38dse
Well-Known Member
Can we have some pics of the light bar for comparison .
Si Click
Well-Known Member
Firstly, if you are linking work lamps of over 3000W to your reversing lights they are not going to get anything like enough power to light them. Which is good because putting 250 Amps through your loom would fry it instantly. The cable required to transmit 250 Amps any distance at 12V is basically a copper bar.
Secondly, you said they were 18W which seemed very sensible.
Thirdly, assuming you have a 150 Amp alternator, even with the engine running and the alternator working at max output, at 3500W you would still have close to a 150 Amp drain on the battery. Assuming you have a 100Ah battery on full charge that means even with the engine running, your battery would be completely flat in under 20 minutes.
Of course you may have a multiple battery 24V system in which case you might get over an hour. But it would still be hideously impractical and I would love to see how you are dissipating heat from a 3.5Kw light which is producing more heat than a 3 bar electric fire.
Shimsteriom
Master Procrastinator
I'd rather have a 100Mbyte Internet connection than a 100Mbit connection
I'd be happy with 25mbps symmetricI'd rather have a 100Mbyte Internet connection than a 100Mbit connection
Si Click
Well-Known Member
3500.. lumens, watts?? who cares, its 3500!!! nobody cares what the words say anymore, its all the same anyways
had a similar discussion at work a while back, bits or bytes? 'its all the same and nobody cares, we're int he 21st century now'
He should care. You and I both know he cannot have a 3.5Kw light. Before he does any more electrical work on his LR he needs to realise that his knowledge of 12V electrical systems is minimal and that he needs to improve it or get a specialist to do the work.
I've seen light bars on eBay stating similar values. It's insane, either lies or not fit for use on a road vehicle, like you said. Kettles can be up to 2500w, and they are water cooled!
I'd believe that. 900ms (milli seconds) is about as long as your battery would last
Whittam9090
Member
Hi guys its actual 3,500 lumens the description on ebay says its 3,500lumens I know another lad he had a look and he said its same as his 3,500lumens don't get me wrong there bright as here I get roughly 200m viewing distance in dark so I'm i right guessing there 900w ?
Whittam9090
Member
If this helps its on a 40amp so its ran off the battery with a relay and it has a built in fuse box on the wiring with a 40amp ?? I get a range of 200m viewing on it . Its like daylight when its on
Si Click
Well-Known Member
If it is on a 40 Amp fuse then it is probably rated to 30 Amps which would make it 360W which makes it a very decent light without being a liability in terms of heat and power drain.
For me this thread has been about trying persuade the original poster than he needs to understand 12V electrics a bit better before he starts fiddling with it.
For me this thread has been about trying persuade the original poster than he needs to understand 12V electrics a bit better before he starts fiddling with it.
neilly
Well-Known Member
So I asked before, but you are not answering.
How do you get the cable into the car if you cannot bend it?
Also can you supply a link to the supplier?
Cheers
Nodge68
Well-Known Member
If the output is 3500Lm (which is **** poor by the way) then you won't need anything like a 40 Amp circuit to drive it. I bet it uses 3 Amps tops, because a 3500Lm bar will be rated about 30 Watts.
You can get a rough idea of how many lumens are available from a light bar, simply by multiplying the number of individual LEDs X 300, this will get you in the ballpark.
For example, my 22" light bar has 42, 3 Watt CREE emitters, each emitter making approximately 300Lm. So 42 X 300 =12,600 lumens, which is pretty representative of an off the shelf CREE light bar. This same light bar will have a power rating of 126 Watts, which is about 10 Amps on a 12 V (nominal) vehicle electrical system.
You don't need to worry about voltage drop or anything complicated, as these LED bars use DC to DC converters to drive the LEDs, so providing the power cable can supply the current without melting, it'll light the bar just as bright as a monster thick cable would do.
Last edited:
