Amperage inflation mystery

[the paws]

I bought some Nite Light led lights advertised at 60 watts each. Putting two of these on a 10 A AUX switch worried me. Using conventional calculations (60 watts divided by 12 volts equals 5 amps each, times 2 lights equals 10 amps, or on the verge of blowing the 10 A fuse). So, I thought I’d measure the actual amperage draw.

With a 30A gage, I connected a 12 volt li-ion battery (actually at 13.5 V) up to one of the lights. I expected The gage to read at least 5A. With the light burning bright, the needle barely moved. I thought the gage was bad. So I hooked the battery up to a 2 ohm power resistor. Wala, the gage reads about 6A. Using V= A x R, it checked out. And using watts = V x R, the power usage was 72 watts.

I flunked the new math, so I thought I’d check another way. I replaced the power resistor with the light and in-line fuses, starting at 5A. I got all the way down to a 1/2A fuse before it started to glow, but did not burn out. So, here’s a lesson in new math.

P (watts) for LEDS is V x A x 10. So if a vendor is selling a LED rated at 600 watts, then the current draw will be 5A at 12v. So, your 10A Aux switches should handle a LED light rated by the manufacturer at 1200 watts.

Sounds like watt inflation to me. Or new math,. Or magic LEDS. Comments.?

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[Tmkimler]

Really, it’s probably the supplier rating it higher to protect their component for the user and warranty sake. Nothing wrong with having a safety factor, even if it’s 20x

 

[MileHighCitizen]

What is this "new math" you're on about?

Watts = Volts x Amps. What is this multiply by 10 you are doing?

Also, it's voila not "Wala."

 

[Techun]

What is this "new math" you're on about?

Watts = Volts x Amps. What is this multiply by 10 you are doing?

Also, it's voila not "Wala."

Calm down gramps

 

[toymaster]

What we have here is a "failure to communicate", that happens when advertisers lie. Noticed the chinese companies play it fast and loose with the facts.

Let me do a little explaining and I have also supplied a link for some light reading...see what I did there

There is a reason LED's are not measured in "watts". Also, the voltage of those lights are 9-30 vdc. You are using a nominal 12V for our calculations. I'm sure if you pumped in ~30V into them you could get close to 60W of power usage. Read the article below and let us know if you need some more splain'n

1-Watt, 3-Watt & High Wattage LEDs Explained (ledsupply.com)

 

[Billnchristy]

Probably because there is no effin way they are 60w.

 

[Djstang2011]

LED Lights advertised at "X" watts usually means brightness, not actual power consumption.

 

[MileHighCitizen]

Calm down gramps

 

[KABQ]

LED Lights advertised at "X" watts usually means brightness, not actual power consumption.

This is absolutely correct. LED bulbs for your house are listed as a wattage equivalent. For example a 120W LED bulb may only draw 10W of power but the brightness is similar to a 120W incandescent bulb, making it easier for consumers who are unfamiliar with LEDs.

 

[the paws]

Thx Toymaster. The article was interesting. But, still, at 13.5 volts actually drew less than a 1/2 amp. So, it’s still a mystery. Maybe the forward voltage os actually 120 volts times 1/2 amp equals 60 watts. In any event, before connecting something to your Aux circuits, some checking would be in order. In my case, it looks like a 10A circuit could handle 20 of the “60 watt” lights. Hummm.

BTW “wala” is an advanced engineering word. Voila is a bastardized French word. So there! LOL. Voila is pronounced wała. So there!

 

[the paws]

Well, as it Turns out Led watt ratings have nothing to do with volts and amps. Its Lumens divided by the led’s efficacy. So, you need a lumenometer and an assumed efficacy to determine a lights “wattage.” Isn’t that special? https://www.rapidtables.com/calc/light/lumen-to-watt-calculator.html

 

[dgorsett]

So, I'm not crazy, well maybe I am but not for this. I've never understood the wild wattage ratings some were claiming for their LEDs. I've installed cheapo LED lighting kits with the included relays, and I've wired bare lights in direct with no issues, this 'splains it.

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