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Old 12-31-2013, 06:09 AM   #1
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LED help


im making a 60 LED IR panel

but i need some battery help

its for my night vision camera

here is the diagram i found for my build
look at the last one on the page

http://led.linear1.org/led.wiz
^simple build

and im using these batteries
http://www.amazon.com/4pcs-Panasonic.../dp/B00C26OWGS

so 4 of them makes

13,000mAh
and 14.4 volts

my question is will these batteries work and if so what kind of run time am i looking at?

thank you

-Brennan

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Old 12-31-2013, 07:27 AM   #2
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LED help


each 100 ohm resistor dissipates 360 mW
  • the wizard says the color code for 100 is brown black brown
  • the wizard thinks 1W resistors are needed for your application
  • together, all resistors dissipate 3600 mW
  • together, the diodes dissipate 5400 mW
  • total power dissipated by the array is 9000 mW
  • the array draws current of 600 mA from the source.

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Old 12-31-2013, 09:50 AM   #3
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When you put batteries in series, you don't add up the mAh capacities. You will have 3600mAh @ 14.4v. If your array draws 600mA, then you will get a theoretical 6 hours of use. Practically, probably more like 5 hours.
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Old 12-31-2013, 12:17 PM   #4
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oh sweet!

thank you!
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Old 12-31-2013, 01:13 PM   #5
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Be aware that those lithium cells MUST have over-discharge protection. If you just let them run down all the way, they will be destroyed.
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Old 12-31-2013, 04:42 PM   #6
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they have a cut off at 3.0 volts if thats what ya mean,
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Old 12-31-2013, 05:12 PM   #7
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You can add the voltage or you can add the current not both. If you run them in series you get 14.4 volts but the capacity is still 3400 mAh. A single LED typically draws about. 15 ma. High output ones will draw more. So 60 will be about 900 ma. 3400 divided by 900 gives a run time of about 3.7 hrs.

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Old 12-31-2013, 05:27 PM   #8
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^ thank you!
im new to this type of things

i built it and it works pretty damn well!


but they sent me 4500mAh batteries

so to get the run time i take the

mAh batteries
devided by
the draw from device?

knowing that would solve a lot of my questions

and i have a standers rocker on/off switch

is it possible to add a potentiometer that when turned all the way down it clicks off? it would be nice to adjust brightness because indoors its too damn bright and would be nice to have a adjustment know on it

thanks everyone who chimed in to help

Last edited by k20crx; 12-31-2013 at 05:31 PM.
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Old 12-31-2013, 05:32 PM   #9
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sorry for the "noob" questions lol
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Old 12-31-2013, 05:50 PM   #10
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Yes, divide the total mAh by the current draw to get the run time in hours. What are the specs on the LEDs you're using? Just curious.

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Old 12-31-2013, 06:02 PM   #11
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Quote:
Originally Posted by k20crx View Post
^ thank you!
im new to this type of things

i built it and it works pretty damn well!


but they sent me 4500mAh batteries

so to get the run time i take the

mAh batteries
devided by
the draw from device?

knowing that would solve a lot of my questions

and i have a standers rocker on/off switch

is it possible to add a potentiometer that when turned all the way down it clicks off? it would be nice to adjust brightness because indoors its too damn bright and would be nice to have a adjustment know on it

thanks everyone who chimed in to help
mAh = milliamp-hours = milliamps multipled by hours. 4500mAh = 4.5 amps for one hour, 450 milliamps for ten hours, or 45mA for 100 hours. As long as the discharge rate isn't too fast, this rule is true. You lose capacity with fast discharge, so if the batteries are being drained in less than a couple hours you'll have reduced capacity available. The capacity is measured from fully charged to fully discharged, where "fully discharged" means the cutoff at about 3.0V, maybe 2.75. In practice, you do not want a cutoff voltage that low. 3.0V is as low as you can go, and 3.2V is better for cell life.

A plain potentiometer cannot be used to dim this kind of load. It will burn up. You could use a big hefty power rheostat, but it's extremely inefficient. Dimming a load like this really needs to be done using an electronic PWM dimmer. They are out there and can be bought pretty cheap.
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Old 12-31-2013, 07:19 PM   #12
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Quote:
Originally Posted by mpoulton View Post
mAh = milliamp-hours = milliamps multipled by hours. 4500mAh = 4.5 amps for one hour, 450 milliamps for ten hours, or 45mA for 100 hours. As long as the discharge rate isn't too fast, this rule is true. You lose capacity with fast discharge, so if the batteries are being drained in less than a couple hours you'll have reduced capacity available. The capacity is measured from fully charged to fully discharged, where "fully discharged" means the cutoff at about 3.0V, maybe 2.75. In practice, you do not want a cutoff voltage that low. 3.0V is as low as you can go, and 3.2V is better for cell life.

A plain potentiometer cannot be used to dim this kind of load. It will burn up. You could use a big hefty power rheostat, but it's extremely inefficient. Dimming a load like this really needs to be done using an electronic PWM dimmer. They are out there and can be bought pretty cheap.

ohh okay i wasnt sure, i will just use it at full power!
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Old 12-31-2013, 07:22 PM   #13
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  • Diameter: 5mm
  • Color: Water clear
  • Voltage: 1.3-1.6VDC
  • FC:50-65mA
  • Wavelength: 850nm
  • Angle: 60 degree

heres the specs
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Old 12-31-2013, 08:44 PM   #14
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Ok. I didn't play with the web based calculator but it looks like they draw more current then I guessed. If each one draws the minimum of 50 ma, then 60 LEDs will draw 3000 ma. I don't think those batteries will power it for much more than an hour. Can you get a power supply to run them?

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Old 12-31-2013, 11:24 PM   #15
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Well I played with the LED wizard and set the voltage to 7.2 volts. A 60 LED array can be built with 4.7 ohm resistors and only draw 600 ma. Much better than I thought. Good luck!

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