Max volts for a 3w IR LED question

southport

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Advertised on a well know auction website as 'China Made 3W IR Infrared CREE LED'

OK so I bought one to drop into the torch that was has/had a UV LED set up, running of three standard AAA's

This IR LED states required voltage as 3v - 8.4v, yet I have seen on t'interweb the same one upto 9v and I think a 12v version, and I assume they are all the same IR bulb (can you call them bulbs?)

Obviously to get the best out of it, I need the max voltage, so instead of using 3 x AAA (4.5v) I am using 2 x Surefire 3.7v and a dummy AAA, giving me a theoretical 7.4v or I guess 8.4 when newly charged.


Has anybody tried these 3w IR things and on what voltage, I am thinking of taking out the dummy and popping in a 3rd 3.7v cell, giving me approx 11.1v - or will that blow the IR ?
 

Robin24k

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Maximum voltage for the LED is definately not in the range of 3V+, I would expect it to be around 1.5-2.0V. It's probably referring to maximum battery voltage that the driver can handle, and that should not be exceeded or you will fry the electronics.

You should be getting the same performance with 4.5V or 8.4V, so I would just stick with AAA's.
 

Gunner12

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LEDs often come with a driver, or a circuit that controls the voltage and current to the LED. A LED can be hooked up to multiple different drivers of different specs, so one might be 0.9-4.2, another might be 3.7-7.4v, but both can have the same LED at the same brightness.

I'd stay within the limits of the driver. A god driver will keep the power to the LED constant (or close to that, not always possible) withing it's voltage limits, so you should get the same output with different voltages. If you want more output, you'll need a more efficient LED, driver, or a different driver.
 

southport

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Interesting technical facts, thanks for the help.

I assume then, that the 36 LED drop-in upgrade I have for my 2 x D MagLite will not burn any brighter if I increase the volts from 3v (2 x D cells) to say 9v by using a 6 X AA to 2 x D adapter, it'll be no brighter than on 3v but shine for longer ?
 

Gunner12

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Runtime depends on battery capacity, not voltage. A tiny A23 battery has 12v, just a like a car battery, but the car battery will last substantially longer then the small battery. A D-cell has 10-20 Wh (Watt Hours) depending on factors (chemistry, brand, etc), a 9v battery has 2.4-5.7 Wh depending on some factors, a AA battery has 2.5-3.5 Wh. So, 6 AA batteries will give you 15-21 Wh, less capacity then two decent D cells. Assuming the drop-in can take the voltage, you probably won't see better runtimes.
 

southport

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Runtime depends on battery capacity, not voltage. A tiny A23 battery has 12v, just a like a car battery, but the car battery will last substantially longer then the small battery. A D-cell has 10-20 Wh (Watt Hours) depending on factors (chemistry, brand, etc), a 9v battery has 2.4-5.7 Wh depending on some factors, a AA battery has 2.5-3.5 Wh. So, 6 AA batteries will give you 15-21 Wh, less capacity then two decent D cells. Assuming the drop-in can take the voltage, you probably won't see better runtimes.

. ....again, great technical info for my learning curve, but it doesn't answer my question - which was :

Would increasing the volts supplied to my 36 LED drop in for a 2 x D cell Maglite running on 3v, would it burn brighter on 7.2v supplied by a 6 X AA to 2 x D adapter (which is what brought me to these forums)

Its a nice drop in, and for me is very bright on 2 D cells, but the same drop in is supplied for bigger Maglites upto 6 D cells .

Also, I have a lot of AA Eneloops, using an adapter I can use 6 x AA giving 7.2v nominal- but would I get a brighter light ?

If not I can get a couple of cheapy 2 x AA to 1 D cell holders, wired in parallel to give 1.2v (for rechargeables), using 2 gives me almost the same as 2 standard D cells
 

Gunner12

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I have no idea. Without seeing the actual circuit, I don't know how it will perform at different voltages. Even if I did see it, it'll take me some time to figure it out (not an electrical engineer).

If the drop-in is rated to 7.2v or more, then you could just try it and see if it is brighter. If it is not, then I'm not sure.
 
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