Led lighting question

[Justasquid]

So realizing the factory cab lights do not shine where I want them, I have ordered a set of led replacements. I‘ve used quite a few different pods and bars on sidexsides and boats over the past few years. But this is the first time using them for a tractor and discovered something a little odd. most of the pods I’ve used have been 18-30 watts, so amp draw was never a concern. However, these are stated as 120 watt each. I’ve tested them and they are plenty bright and the pattern is great with the flood/spot combination. But measuring the actual amp draw, they are only pulling 3 amps at 12 volts. If they were in fact 120 watt, they should be 10 amp draw. I’m not disappointed, in fact I’m pretty happy the power draw is less which means I can actually use the factory wiring and switch with them instead of having to use a new wiring harness with switch and relay like I originally planned.

I guess my question is, are most led bars rated at actual power consumption or are they under driven so they get more hours of use and are actually far less than advertised? Each light has a 3 watt led with each light containing 40 leds. These are the cheaper eBay/Amazon 7 inch spot/flood combustion lights. ive had good luck with them in past, so I am not concerned with the quality, but I have never had the need to actually measure the amp draw. they do list them as 120 watt, not 120 watt equivalent. Even stating 12000 lumens of light. Again, not disappointed in the performance as they are super bright and have a really wide pattern. Just curious as to others experiences.

 

[Roadworthy]

I don't know about most LED light bars, only mine. It was advertised as 240 watts. That calculates put to 20 amps so I started thinking how to supply them. I measured the current draw at 5 amps. My mental calculations puts that at 60 watts not 240. That caused me to conclude they were rated for brightness equivalent to a 240 watt incandescent light. That suited me just fine. They're plenty bright.

 

[mikester]

You need to go by Lumens to compare light brightness and Watts for power consumption.

Don't trust the "watts equivalent" or any other such measures because they mean nothing and are marketing clap trap.

I always look at lumens output first then the power consumption. Lumens is what you see, power consumption is what you pay to operate the lights. I look for high lumens low watts.

 

[GreensvilleJay]

As M says ..look at the 'lumen' rating..
watts for LEDs is like watts for stereos... a misused, puffed up number, virtually meaningless.
Ie. there's NO way you can get 100w stero out of a USB powered computer speakers.....

you do NEED to measure what current they do use though, so that you can add the correct fuse inline.

Another factor to consider is the 'colour' of the LEDs. The rating is in Kelvins ( *K). The higher the number the 'whiter' it is. You can have 2 LEDS, same lumen rating and one wil look brighter.....

 

[je1279]

I agree with using lumens for brightness as well but be aware that most Amazon/eBay vendors exaggerate the actual lumen output. Some by a laughable amount.

 

[dochsml]

Just to take a stab at answering your question. LED's are actually diodes (essentially check valves for electricity). LED's have a voltage drop across them, but not a resistance measurement. LED's also have a current rating that they can handle. If you know the voltage (12VDC, 13.8VDC, 14.4VDC), you can translate that current into a wattage. Here is where I'm guessing.... LED light bars come with additional circuitry. In this circuitry, whatever resistance would be part of it. So, it could very well be that the LED itself can handle 10 amps, but the circuitry runs it at 3 amps. Just like with your car. It may redline @ 7000 RPM, but you wouldn't want to drive it that way all the time. Also, you have to be careful of wattage measurements as others have already said. Wattage means you know the voltage. What voltage did they use to get that 120W? I used to buy 100W bulbs rated for 130V. When I switched on 120V, I didn't get 100W. But, I did get a bulb that lasted longer.

 

[GreensvilleJay]

LEDs are actually prefer to run in 'constant current' ( nature of the beast) so, as long as you supply a voltage greater than 3.2 for a white LED, it comes on.... greater current ,,,the brighter it gets.
MFRs cheap out and some use a simple inline resistor to limit current. I prefer 'old skool', do it right, power them from adjustable constant current source.

 

[Justasquid]

Thank you for the replys.

While I am completely satisfied with the light output, my only real concern is if I didn't measure the actual amp draw, I would have used the information given from the light manufacturer. So if I fused the system for the calculated 10 amp per light and had 4 lights in a system, I would fuse the system for a minimum of 40 amp draw, but my actual light draw is only 12 amps for 4 lights. I guess I wonder how "protected" my lights would be if my fuse size was that much higher than it needed to be. It seems at some point, there could be an issue with a fuse that would be too large.

 

[dochsml]

Thank you for the replys.

While I am completely satisfied with the light output, my only real concern is if I didn't measure the actual amp draw, I would have used the information given from the light manufacturer. So if I fused the system for the calculated 10 amp per light and had 4 lights in a system, I would fuse the system for a minimum of 40 amp draw, but my actual light draw is only 12 amps for 4 lights. I guess I wonder how "protected" my lights would be if my fuse size was that much higher than it needed to be. It seems at some point, there could be an issue with a fuse that would be too large.

There are two basic reasons to fuse something. One is to provide short circuit protection (keep the wire from getting so hot it catches fire) and the other is to protect the device (your lights). Most of the time, short circuit protection is what is trying to be achieved with fusing. This is a function of the size of the wire being used (14 AWG is good for 15 amps). Protecting the lights themselves is a little trickier. Do the lights not have some sort of internal fuse already? If so, I'd stick with short circuit protection fuse near the battery.

 

[je1279]

As dochsml said, you should fuse based on the wire gauge that you are using. Choose a wire gauge that will support the actual amperage draw of your lights then select the fuse based on the wire gauge.

 

[RCW]

I remember a similar discussion regarding lumens and amp draw a few years ago.

Long story short, there were a couple folks that said amperage draws were pretty small compared to that one would expect. They were much more savvy in the subject than I was.

This thread reinforces that.

 

[mikester]

Thank you for the replys.

While I am completely satisfied with the light output, my only real concern is if I didn't measure the actual amp draw, I would have used the information given from the light manufacturer. So if I fused the system for the calculated 10 amp per light and had 4 lights in a system, I would fuse the system for a minimum of 40 amp draw, but my actual light draw is only 12 amps for 4 lights. I guess I wonder how "protected" my lights would be if my fuse size was that much higher than it needed to be. It seems at some point, there could be an issue with a fuse that would be too large.

If you are using an OEM wiring harness the LEDs will draw a lot less current than OEM halogen bulbs. I would be careful running a 40A fuse on an existing wiring circuit made to handle 10A.

 

[chim]

My practice is to run a wire large enough so the voltage drop isn't a concern and fuse the circuit at a value that protects that wire. Fusing to protect a light doesn't make sense. If the light draws too much current, it's because it has already taken a crap.

There are some circumstances in building wiring where individual fixtures are fused. They generally have circuits feeding them that could provide current far in excess of what it would take to burn off the teensy wires in them.

 

[GreensvilleJay]

re: only 12 amps for 4 lights. I guess I wonder how "protected" my lights would be

Since LEDS don't have he huge inrush current that incandescent lights do ,I'd use a 15 amp fuse. That'll protect the wiring to the LEDS.
Actual LED 'protection' is a different story. These units are so cheap I doubt they have any real protection but you'd have to open them up to see what's 'inside'. White LEDS need 3.4 volts so typically mfrs run 3 in series ,then a current limiting resistor to drop the +12 down a bit. That is the minimum circuit. To protect from overvoltage, you need to add a zener diode and perhaps a MOV, TVS. Some EMI protection would be nice, heck ad a micro to properly control the LED as well. All this 'stuff' costs money,both in R&D and product making. Can you 'protect' and LED, sure....it'll just cost a LOT more. I've got LEDs that can and have withstand nearby lightning strikes, so I know .

 

[GeoHorn]

It is defective logic to believe the purpose of a fuse is to protect the appliance. It is not.
The purpose of a fuse is to protect the circuit that serves the appliance.
If the appliance draws X-number of Amps at a certain voltage (I.E. Watts) then it should be served with the appropriate gauge wire in the circuit so the proper voltage/Amps reach the appliance. If a wire is rated at X-Amps then it should be served via a fuse or C.B. which will “blow” at amperage above the safe rated. (Some circuits allow a slight overage for “surge”, but generally speaking this is true.)

The fuse does NOT protect your L.E.D.s or your radio or toaster or whatever. It protects the wire so that if a short should occcur...the wire will not become incandescent and start a fire. That’s all.

 

[Justasquid]

For anyone following, I have the led lights installed and they are flat out amazing. They have a very wide pattern and shine much further than the factory cab lights. Being the spot/flood combination, they work really well for my applications. These ended up pulling 36 watts each (3 amps) @ 12 volts, instead of the listed 120 watts, so I was able to use the factory wiring, switch and fuse. they don't fit quite as nice as the factory ones , but they look decent and I am very pleased with the light output. For $30.00 on Ebay, I am very pleased. I will probably add a set to the rear, but probably only flood for the rear.

 

[SidecarFlip]

the wire will not become incandescent and start a fire. That’s all.

Actually, before it glows, it stinks.....

 

[SidecarFlip]

On both m y M's I have 4 facing forward and 2 rearward and my only prerequisite for any SMD light is, it has to fry your eyeballs if you look into it from 20 feet away and mine do, in spades. With my fronts on, I can see clearly for about 1/4 mile. I'm good with that. Rears, not quite as far but they still are eyeball fryers. OEM Kubota lights basically suck and so do the headlights. Replaced them with SMD's as well. In fact every bulb is an LED on both tractors now.

Kubota has to have the weakest headlights known to man. Light output is equal to a flashlight with shot batteries.

I run after sunset a lot on the road, I require good lights, coming and going.

 

[GreensvilleJay]

possible reason why the watts are lower....
Most LED lights soldwork from xx to yy volts ( say 12-24). If they're run in constant current mode( how they work..) then at 3 amps draw....running them off 12 volts, makes them 36 watts, run off 24 and they're 72 watts...NO change in Lumens( brightness).

 

[Justasquid]

possible reason why the watts are lower....
Most LED lights soldwork from xx to yy volts ( say 12-24). If they're run in constant current mode( how they work..) then at 3 amps draw....running them off 12 volts, makes them 36 watts, run off 24 and they're 72 watts...NO change in Lumens( brightness).

Thank you for your input.

I had thought about this as well, being these leds are rated from 9-30 volts. But, I assumed there were resistors built into the leds that would compensate for different input and not allow greater wattage. I assumed the actual leds received the same amount power between that range, and figured they had some sort of resistor. I tested them at various voltages, and noted the amperage change. I would see a 3 amp draw at 12 volts, but a 2.5 amp draw at 14 volts. This points me to thinking the lights are only 36 watts no matter what the input voltage is.

I was just a bit surprised at how much less consumption there is than I originally planned for. I will just be sure to get the lights and test them prior to purchasing wiring and fuse blocks in the future.