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Led light Answered

I'm struggling understanding what im really needing and could use some guidance... I'm tring to build a underwater fishing light that has 36 3watt green leds.  I'm going to only be powering them when the engine is off and the batteries aren't being charges... it will run off a standard 12volt marine battery... the led specs are ' green (510-530nm):DC Forward Voltage:3.4V~3.8V Forward Current: 700mA'.  what would be the best way to power these leds... im assuming that I need to power in series groups of 3. but with such a wide voltage of 3.4 to 3.8... do I just shoot for the middle? do I use 12v in my calculation or do u use like a 12.5 or 13 like it sometimes checks.... Can I get by powering it with just resistors or do I need a led driver? I have entered my data in some of the calculaters online and it says I need a 2.2 resister but gives warnings... and doesn't say what watt resistor... does it matter... first project ... confussed to say the least



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4 years ago

IMHO your best option would be to simply buy an underwater light....
Running LED's in series only works good if the single LED have identical electrical characteristics - otherwise they love to fail premature.
3W LED's always need a suitable driver and not just a resistor.
Wether you can run 3 each in series or not depends on the voltage and specifications of the LED's driver.
In any case your battery will be empty fast.