Actual power draw of LEDs

[ficklejester]

I'm getting more into learning about the wiring of LEDs with plans to build a panel at some point.. I've read here and elsewhere that LEDs are most efficient when driven lower than their full/rated wattage and understand that concept. So it makes sense that a commercial panel that is, for example, 500W actually only consumes maybe 350W.

I've read of ratios, 1.6 or 1.8, etc to use to calculate the actual power consumption in relation to LED rated wattage, but is there a common ratio here? I'm familiar with Ohms Law so I know it must depend on the current of the driver, but do most commercial panels use a single AC driver or the AC to DC drivers like I see a lot in the DIY threads? Are there any resistors along the circuit? I wouldn't imagine there would be if you're hand picking a very wattage-specific DC driver. TIA for any info.

 

[SupraSPL]

The vast majority of LED lamps are marketed based Wattage numbers that are simply "made up" fantasy numbers which are useless to determine the lamp's output.

To evaluate a lamp we start with actual power draw. Some of that power is then dissipated as heat in the power supplies and fans and that can vary quite a bit from lamp to lamp but I estimate about 15%. So then we look at actual LED dissipation Wattage. Some of the dissipation wattage becomes photons but most becomes heat. In order to figure how much of each, you have to consider the efficiency of the LEDs which depends on their quality, their drive current and their running temperature. 30% efficiency is common among the best commercial lamps. Finally, there are losses due to covers, lenses and scattering and that can vary quite a lot from one design to another but I estimate about 10% lost.

So if you know the dissipation wattage and the LED efficiency, you can arrive at PAR W (actual photons) and then calculate the lenses losses and you get PAR W per sq ft.

Our goal as indoor growers is to get photons to the canopy efficiently and as you can see there are many factors working against that goal. DIYers are raising the bar by using large COBs so we can run them soft without excessive cost (up to 60% efficient in some cases but 40% is a great goal), we run them cool and we can avoid the need for lenses and covers. We can also use fans more efficiently and use very high efficiency drivers.

 

[ElfoodStampo]

From what I've taken apart and repaired the banks of diodes are arranged for the driver. I assume for longevity they're not pushing their respective LED's to their max. I'm interested in what makes you believe that running diodes at less than 100% is better for them. What brought you to that?

 

[ElfoodStampo]

I asked that because when LED's came out there was no dimmables. Now they're available, but originally It was either on or off. With a dimmer you have some sort of resistor, and eventually I would expect that to fail, if your dimming.
I just bought a bunch of Lighthouse 8W dimmables and I'm weary of adjusting because I don't want to wear out the driver.

 

[SupraSPL]

The phenomenon is called current droop. As you increase the current toward max, the efficiency drops. So even if you were able to maintain a very low temperature and plenty of longevity, the LED still suffers from current droop. Here it is demonstrated n a graph. The blue line represents what the output would be if there were no current droop and the black line represents actual performance as current is increased and temperature remains steady (Cree XTE used for example)

 

[SupraSPL]

So based on that graph, I run XTEs at 700mA or lower. 700mA drivers are plentiful and cheap. Dimming drivers on the other hand are scarce and expensive unless you use the high voltage Mean Wells. So if I wanted to run an XTE string even softer I would just use a 450mA or 600mA driver which are a dime a dozen and easy to find.

 

[mc130p]

From what I've taken apart and repaired the banks of diodes are arranged for the driver. I assume for longevity they're not pushing their respective LED's to their max. I'm interested in what makes you believe that running diodes at less than 100% is better for them. What brought you to that?

do you drive your car at redline all the time?

 

[ElfoodStampo]

do you drive your car at redline all the time?

My car no, but other motors, yes, like any kind of dc drive motor. I see what your saying but a car motor has no parallel with a LED. ICE use oil and all sorts of other shit that an electric "motor" doesn't use. A LED is not a bunch of moving parts its a resistor..

 

[ElfoodStampo]

So based on that graph, I run XTEs at 700mA or lower. 700mA drivers are plentiful and cheap. Dimming drivers on the other hand are scarce and expensive unless you use the high voltage Mean Wells. So if I wanted to run an XTE string even softer I would just use a 450mA or 600mA driver which are a dime a dozen and easy to find.

Dude, it sounds like you know what the fuck your doing. Thanks for the info, I had no idea!

 

[SnapsProvolone]

do you drive your car at redline all the time?

Not MY car, but a rental hell yes.

 

[Abiqua]

My car no, but other motors, yes, like any kind of dc drive motor. I see what your saying but a car motor has no parallel with a LED. ICE use oil and all sorts of other shit that an electric "motor" doesn't use. A LED is not a bunch of moving parts its a resistor..

No, but the function is similar.

One motor driven at normal cruising and idling speeds will last for years if not decades and be more "fuel efficient".

Another motor even built up to enhance cooing and horsepower will still burn out quickly at top rated rpm and still is more expensive. They also suffer a "current droop" in the upper bands of rpm....

A soft driven LED with be at its ultimate efficiency in regards to temperature, the lower in current [amperage] you go.

An led driven hard, will need expensive cooling and more power at the expense of very thin slice of the light band [i.e. current droop] and probably not last long if something goes wrong.

 

[mc130p]

Not MY car, but a rental hell yes.

I'd drive rental lights at 100% too, lol.

 

[SnapsProvolone]

I drive all my HID lights at 100%.

 

[SnapsProvolone]

Sometimes overdrive in flower.