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LED power usage calculations- am I doing this correctly?

AKCub

Junior Member
#1
Hi,
I am running a electrohub quad with a 3s 2200 mah battery setup. I added strip LED's to the arms for perspective and to play at night. I think I figured the power usage of the LD's correctly but can someone back me up?

The LED's are advertised at 4.8 watts/meter. I have .81 meter (81 cm) so 3.88 watts.

So 3.88 watts divided by 12 volts = 0.323 amps or 323 mA for the LED's

Does 323 mA sound right for 3528 LED lights? Can I take that right out of the useable mA/h rating of the battery (2200-323 mA)? Other than flying the quad (I have and the lights look great) is there a way to predict how much of a hit my flying time will take with lights on?

Thanks,

Scott
 

Cyberdactyl

Misfit Multirotor Monkey
#2
Those numbers can have several variables effect it.

Under normal flying around, I am pretty sure you will not notice the load or the flight time reduction by a standard 1 meter LED strip off a 2200mAh battery. What I'm saying is, one less brief push of the throttle among the few dozen flying around, will negate all the time loss of the lights.
 

AKCub

Junior Member
#3
Thanks,
I kinda figured as much but didn't have any science to back that up.

Scott

Those numbers can have several variables effect it.

Under normal flying around, I am pretty sure you will not notice the load or the flight time reduction by a standard 1 meter LED strip off a 2200mAh battery. What I'm saying is, one less brief push of the throttle among the few dozen flying around, will negate all the time loss of the lights.
 

RichB

Senior Member
#4
Does 323 mA sound right for 3528 LED lights?
Is 3528 a model number or a count? If it's a count, then yeah I guess that's possible if they are small LEDs and they must be to cram that many of them on a .8-meter strip.

With that being said, your math checks out, and it is right about where I would expect for that length of LED strip, which commonly run about 400mA per meter.

Can I take that right out of the useable mA/h rating of the battery (2200-323 mA)?
No, you are mixing up milliamps and milliamp-hours

If you plugged the battery in and let the lights run for one hour before flying the quad, then yes, you could assume that the battery had somewhere around (2200-323) maH remaining when you started flying.

Other than flying the quad (I have and the lights look great) is there a way to predict how much of a hit my flying time will take with lights on?
Assuming that your 2200maH battery lasts you 10 minutes, your motors use approx (2.2 * (60/10)) = 13.2 amps. The lights draw approx 0.3 amps.

There will be almost no noticable change in flight time
 

AKCub

Junior Member
#5
The 3528 is (I think) a designator for the size of the LED's. Another common one is 5050.

Is 3528 a model number or a count? If it's a count, then yeah I guess that's possible if they are small LEDs and they must be to cram that many of them on a .8-meter strip.

With that being said, your math checks out, and it is right about where I would expect for that length of LED strip, which commonly run about 400mA per meter.



No, you are mixing up milliamps and milliamp-hours

If you plugged the battery in and let the lights run for one hour before flying the quad, then yes, you could assume that the battery had somewhere around (2200-323) maH remaining when you started flying.



Assuming that your 2200maH battery lasts you 10 minutes, your motors use approx (2.2 * (60/10)) = 13.2 amps. The lights draw approx 0.3 amps.

There will be almost no noticable change in flight time
Perfect explanation!

Scott