How many watts / amps for LED light bar?

Timmer92 · Dec 13, 2019

Hi all,

I take delivery of my Kubota L3901 next week. I have a project I want to tackle immediately, and would like to have all the parts here ready to go. I want to add a 12-20" light bar to my ROPS. I am aware there is a prewired worklight connection. Based on my research, that is connected to a 10 amp fuse. I can find LED lights in the 75-125w range, which by my calculation would be up to 10 amps, and therefore would work on that connection. At the same time, there are many units out there in the 150-350w range or even bigger. I am guessing if I'm going to go through the trouble of adding a light, I don't want one that is under powered. I obviously can go with a bigger one and connect it directly to the battery with the appropriate fuse. Given that very few have specs for lumens, watts is pretty much the only measure I have. Any advice on whether I should go with a bigger wattage unit?

Just this fall I was planing rye with the provided headlights on the Kubota I just traded and I think I would have had more luck with flashlight! I would like to do it right.

Thanks!

PROFarms · Dec 13, 2019

I would think that the 75W LED would be plenty enough! We only have one 50W that lights up our yard and that’s very bright. We have 20W in our cattle shed and it’s like daylight in there nearly. I certainly wouldn’t worry about going any higher

Roadworthy · Dec 13, 2019

Watts for an LED is an indicator of power used or required power supply. For your tractor you can divide that by twelve to get the current rating (watts=volts X amps). Since LED lighting uses power more efficiently than incandescent lighting a watt of power feeding an LED will generally give you far more illumination than a watt of power feeding an incandescent. I would not expect to power a device requiring ten amps from a ten amp fuse. That leaves nothing for initial surge current. Either power a relay from that fuse or figure on powering about five amps of lighting.

WranglerX · Dec 13, 2019

Maybe you need to know actual current (amp) values instead of going by watts... As a example this 100 watt, 20 inch light bar puts out 9,600 lumens and only draws 7.33 amps as stated in its specification sheet...

2" Curved Off-Road LED Light Bar - 1W - 9,6 Lumens | Super Bright LEDs

You really need to find amperage draw if you are limited by existing fuse size.... The watt values of light bars and leds can be misleading...

Dale

s219 · Dec 13, 2019

A light bar may be overkill. I have a single round LED lamp forward-facing on my ROPS and it's enough to light up the area like daytime. I have a second light facing rearward. I put them on separate switches, both tied into the work light wiring under the left fender. Each light draws 1.4 amps at 12V.

My tractor LEDs are from 2011, and newer LEDS will be more capable. I put two Rigid SR-M lights on my boat t-top and they are ~2400 lumens and 2A (per light). They are great for coming into my creek at night. I think they would be too bright for my tractor, but it gives you a good idea of the lumens and amperage ballpark. I'd say you should have more than enough light out of 2000-5000 lumens and 2-4A.

Threepoint · Dec 13, 2019

Roadworthy said:
Watts for an LED is an indicator of power used or required power supply. For your tractor you can divide that by twelve to get the current rating (watts=volts X amps). Since LED lighting uses power more efficiently than incandescent lighting a watt of power feeding an LED will generally give you far more illumination than a watt of power feeding an incandescent. I would not expect to power a device requiring ten amps from a ten amp fuse. That leaves nothing for initial surge current. Either power a relay from that fuse or figure on powering about five amps of lighting.

Timmer92, welcome to TBN!

+1 on most of Roadworthy's comments, except that I'm sure you'd be fine with 90w of LED, drawing 7.5A on the existing 10A circuit. Rather than a single light bar, if that is what you have in mind, consider adding two 45w LED floods, one on each side of your ROPS. That will give you more flexibility in aiming the beams. And more than enough light for most any work in front of the tractor after dark.

k0ua · Apr 26, 2021

huddlewalt said:
I am not a fan of such lighting, I prefer environmental energy.

Lightning bugs in a mason jar?

FastEddieR · Apr 26, 2021

Lightning bugs in a mason jar?
_______________________________
I wanted to make a smartass reply too, but restrained myself. Good thing, cuz your reply was way better than mine would have been!

SmallChange · Apr 28, 2021

Perhaps there is an issue here translating between actual watts of electrical power and some sort of equivalent brightness comparing to incandescent bulbs, as huddlewalt mentioned. I kinda think an LED assembly that actually takes 350 watts of electrical power, or even more, will create all kinds of additional problems, such as igniting your neighbor's siding, disrupting local air traffic, and changing local weather.

FTG-05 · Apr 28, 2021

JethroB · Apr 28, 2021

A poster once mentioned the great quantity of bugs a ROPs mounted light bar attracted. That would be a concern if I ever considered them. Any others with that issue?

WranglerX · Apr 29, 2021

Keep in mind Ohms Law..

Volts time Amps equal Watts....Or V x A = W

Or

Watts divided by Volts equals Amps... Or W / V = A

Voltage will always be a constant in calculation whether a 12 or 24 volt vehicle system or 120 volt shop lighting system...

Any lamp source that does not state actually electrical draw is not much help.... The "equivalent watts" or stated "lumens" as a relative description to light output, and may not have any actual relevancy for actually electrical draw....

Ohms Law Calculator

This free Ohm's Law calculator solves for any of the variables in the Ohm's Law equation using various units of measurement and gives out the solving steps.

www.calculator.net

CoyPatton · Apr 29, 2021

One note here that I believe is worth pointing out is that watts, amps and voltage are all electrical terms. They really do not describe brightness.
That is mot to dismiss the need to understand the importance of these electrical terms to the health of your tractors electrical system.
While watts of an incandesce bulb had a bearing on brightness back it the day, as florescent light became popular, the color of the bulb had more influence on thus than wattage.
Now with LED’s wattage has to fo with the start up power required and nothing to do with brightness.
Brightness is now discussed in terms of lumens. And is a more comparable measurement.
Hope this helps.

ededic · Apr 29, 2021

I just wired my refurbished curtis cab with LED lights and the factory cab lights, I used relays and switches as it would be done in the factory. I have used 10 amp fuses for any of the LED lights. I use 20 amp fuses on the wipers and original cab lights. The lights I have are SMD3030 chips emitting 6500K bright light and 3000K super yellow light, providing 120w and 12000lumen.

One thing I would think about is the new LEDs that offer not just the white but the amber light. My light bar that I had installed on the ROPS before the cab was so bright, no one could work in front or in the rear of the tractor without being blinded. I now replaced them with the multi mode LEDs that have Bright white, Amber, Bright white with Amber, White Flash, Amber Flash and Bright White/Amber Alternating Flash. I hooked up a momentary switch to the yellow wire on the lights and change them with a simple bump. The amber light is a nice bright soft yellow the illuminates and does not blind anyone great for working at night with people around the bucket and the back hooking stuff up.

Just a thought.

327 JD 2210 Curtis Cab Dash Installed.png

WranglerX · Apr 30, 2021

ededic said:
I just wired my refurbished curtis cab with LED lights and the factory cab lights, I used relays and switches as it would be done in the factory. I have used 10 amp fuses for any of the LED lights. I use 20 amp fuses on the wipers and original cab lights. The lights I have are SMD3030 chips emitting 6500K bright light and 3000K super yellow light, providing 120w and 12000lumen.

One thing I would think about is the new LEDs that offer not just the white but the amber light. My light bar that I had installed on the ROPS before the cab was so bright, no one could work in front or in the rear of the tractor without being blinded. I now replaced them with the multi mode LEDs that have Bright white, Amber, Bright white with Amber, White Flash, Amber Flash and Bright White/Amber Alternating Flash. I hooked up a momentary switch to the yellow wire on the lights and change them with a simple bump. The amber light is a nice bright soft yellow the illuminates and does not blind anyone great for working at night with people around the bucket and the back hooking stuff up.

Just a thought.

View attachment 696673

A sort of yes, here.... A lot of LED come in different color temperatures expressed in kelvin and I believe 5500/6000 k. is equivalent to sunlight... Anything with larger number tend to be into the bright blue spectrum, where lesser numbers tend to be on the softer brown tones.... The brighter blue spectrum as actually harder on the eyes than the softer shades of brown...

CobyRupert · Apr 30, 2021

Do we know if wattage stated is the actual consumed wattage (Wattage= Volt x Amps) of the lamp, or a measure of its light (lumen) output when compared to an incandescent lamp (of that wattage)?

The voltage of the system might vary between 12.0-14.6V.

Incandescents are like heater elements that glow. LED’s are non-linear devices. Meaning their impedance (resistance) depends on the voltage it’s being measured at, or said another way: the voltage across it. (Sidebar: Most materials act like heater elements when it comes to conducting electricity (unless you coil them or make electrostatic plates). Using ohms law you can determine a materials resistance. Once measured, it’s close to being set like stone. Doesn’t matter what voltage you used to measure. Comparable to a pipe you’re conducting water through. Changing the pressure doesn’t change the physical characteristics of the pipe. It’s still a 1” pipe! LED’s are more like a flexi-hose than a pipe. Mankind has really been able to exploit the non-linear characteristics of LED’s, diode’s (transistors), etc..
..I digress)

“Efficacy” is the measure on how efficiently a lamp produces light from the energy supplied. It is usually measured in lumens/Watt. Incandescents are really poor at this. LED’s are really good.

Light bar vs. floodlight: If they produce the same lumens, then it’s just a matter of how the light is distributed. (Wide, narrow, up, down, etc..)

Remember nothing is free: Just as lighting makes some areas brighter, it makes other areas darker. Lighting is sometimes more about perception than illumination.

SmallChange · May 7, 2021

CobyRupert said:
Do we know if wattage stated is the actual consumed wattage (Wattage= Volt x Amps) of the lamp, or a measure of its light (lumen) output when compared to an incandescent lamp (of that wattage)?

The voltage of the system might vary between 12.0-14.6V.

Incandescents are like heater elements that glow. LED’s are non-linear devices. Meaning their impedance (resistance) depends on the voltage it’s being measured at, or said another way: the voltage across it. (Sidebar: Most materials act like heater elements when it comes to conducting electricity (unless you coil them or make electrostatic plates).

Yes, the question about whether it's actual consumed wattage is a good one! I just finally ordered some small light bars, but it was actually a bit challenging to get this question clear on many of the products I was choosing between. The old incandescent bulbs were convenient to choose based on wattage when you really were interested in choosing the brightness, but newer more efficient lights throw this not-very-correct method of picking them way off.

About lights being like heater elements that glow: there's one very big difference, that impacts electrical resistance and power supply issues. Heater elements are almost always made with an alloy like Nicrome that was designed to have a nearly constant electrical resistivity over all temperatures. But incandescent light bulbs are not, because they operate too hot. Instead, they use elemental metals, almost always tungsten. A single element metal generally has a resistance that is proportional to the absolute temperature, which means its resistance when running is 10X higher than it is when off. If you measure the cold resistance, you'll predict ten times more current draw than it will actually use when it is on -- except during the fraction of a second when you first turn it on before it comes up to temperature. In fact, you need special circuit breakers to handle this very short term inrush of current. That's what they mean by "tungsten rated" on a breaker.

And about LEDs being non-linear devices: the literal LED device itself is very nonlinear, yes. If you buy an LED component from an electronic parts wholesaler you must deal with this. But the products we buy in lamp assemblies have power conditioning circuits to manage this. In fact, if you look on Amazon for 12 V LED light bulbs, you will see even the little bulbs have tiny circuit boards visible inside them, which take care of all that. It may be hard to guess what such an assembly looks like when you measure voltages and currents for it.

Pete O · Apr 3, 2022

I'd be having a long hard think about what you want the lights for; i.e. what you need to illuminate. Lighting up the working envelope of a FEL, for instance, is very different to needing to avoid wildlife on an outback road when travelling at 120km/hr (here it's kangaroos and emus, for you maybe black bear?!). The LED lightbars I use on my vehicle for that purpose are fantastic but would cause a public nuisance and a traffic hazard if I was using them on my tractor around my small property. Anyone working with you, be they on the ground or on other machines (like when harvesting into a towed bin), will be looking into your lights at least some of the time. A few well-placed LED work lamps of modest output would probably more suited to the purpose, and well within the 10a draw.

Helogabals · Apr 4, 2022

I have recently gone trough that
At the end bought this osram

1. it's "combo" beam
2. 30 W = 2... 3 A
3. 1 Lx = 360 m
4. not so big, really tough body. on my ROPS already was holes, this ledbar fit there without drilling anything