# What is the greatest number of leds I can wire to a single power source?

What is the greatest number of leds that I can parallel wire to one power source? If I had a 9v battery could I parallel wire 40 leds to that battery? (including resistors and all that). thanks!?

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8 years ago
A typical rechargable PP3 has a capacity of around 200mAH. That means you could draw approximately, for example, 20ma for 10 hours, 50mA for 4 hours, 100mA for 2 hours or 200mA for one hour. If you're running your LEDs at 20mA, divide 10 by the number of LEDs to give you the run-time - Your choice. If you use a rechargable PP9 at 1800mAH, you could multiply those times by 9. If you're running off a mains adaptor then the limit is the maximum current of the adaptor divided by 20mA. If you used low current LEDs (5mA) you could run 5 times more for but they wouldn't be as bright.
Gus4097 years ago
Hi, Check out the calculator from Capt. Howdy. If you parallel the 40 leds @ 20mA each, they will draw 800mA from your battery (the whole thing depends on the current only). Most 9V batteries give 550mAh so it won't be able to last for more than an hour probably not even half. The calculator sets up a 4(leds serial) by 10(parallel branches) matrix reducing the drawn current to only 200mA. I hope this helps, Good luck.
acidbass7 years ago
well you might want to check the wattage or whatever it is called on LED's but check that and see what it is if it is greater than 9 volts your battery wouldnt light it but if it is like 0.5 volts than you could light 18 with your small 9 volt so what i am really trying to say is that check the voltage on you power source and LED's but it really depends on your power source
milsorgen7 years ago
Avg. LED is 20mA, so 20 x 40 = 800mA you'd have to supply.

Only problem is 9v don't have much capacity with a typical alkaline clocking in at 565mAh.
Capt. Howdy8 years ago
Try this calculator. http://led.linear1.org/1led.wiz
lemonie8 years ago
At some point you're placing severe load on the power source. This datasheet gives various information on the performance of a Duracell 9V battery. Compare what AndyGadget has said to this:
Max output graphed is 100mA giving ~2h service life.
Max power graphed is 1000mW

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