I already connected 14 LEDs, but I don’t inow how many would work for at least 10 min.
Video where I connected 14 in parallel:
We know that each led consumes 20mA, but only for 1/12th of the time because it is flashing. We don't know what current will be consumed when the led is off, but I expect that will be small, so let's assume we can ignore it. So the average current for each led is 20/12 = 1.7mA.
Your battery has capacity of 3350mAh and you need it to last for 10 minutes or 1/6th of an hour. So if your battery can output 3350 x 6 = 20000mA (20A), it would last for 10 minutes. Can your battery output 20A? I do not think so. It might catch fire if you try that.
If we assume your battery can output 20000mA, with each led consuming 1.7mA, you could drive 12000 LEDs.
So it don't think the battery capacity is the limiting factor in your question. It is the maximum current output it can provide which will tell you how many LEDs can be lit.
Thank you @PaulRB . I found that Max. continuous discharge current of my battery is: 4.875A
Am I able to lit 40 LED's for 10 min. with this without catching fire?
If I do 487,5 mA / 20 mA (LED forward current) = 24
That means I can safely lit 24 LEDs with one battery? Is that correct?
I assume you mean 487.5mA?
I posted values like "20000" and "12000" instead of "20,000" and "12,000". Normally I would do that but I saw that you use "," where I would use "." so I did not want to cause any confusion.
Why that value: 487.5mA?
@PaulRB The calculator app on Mac uses , instead of . that's why I used that. I converted the battery discharge current from A to mA 4.875A and I got 487.5 mA and then divided that value by the LED consumption (20mA) and I got 24.375 that means I can lid 24 LED's with this battery safely before catching fire?
Yes, I know how you got that value. I was hoping you would realise your mistake when I asked you about it.
Yes @PaulRB , but is my logic right? The maximum no of LEDs is 24? Because I don't want my battery to explode since I use this close to my face.
No.
4.875A is 4875mA, not 487.5 mA.
The LEDs are not truly 20mA each, they average 1.7mA. Only if every led in the circuit flashed perfectly in step would the 20mA number be important. I don't think that will happen.
Thank you @PaulRB so what is the maximum no. of LEDs I can use?
I don't actually see a maximum mA rating... But since it's rated at 3200mAh I wouldn't push it past 3200mA.
The 3200 mAh rating is milliamp hours which means you can get about 3200 hours at 1mA or 1 hour at 3200mA etc. This is an energy rating or battery life rating.
Both of those calculations are probably optimistic and you are more-likely to get the full-rated mAh at around 100mA, which would be 32 hours.
3200/20 = 160 so it should be able to power 160 LEDs for about an hour. Of course the battery will be partially discharged so the LEDs will be dimmer after an hour.
If you calculate the resistors for 10mA you can get twice the battery life or you can power twice as many LEDs.
The LEDs should be connected in parallel with a resistor for each LED.
I'm not sure exactly how LEDs with built-in flashing circuits work. Will they operate correctly with a resistor in series? The voltage dropped by an external resistor, and so the supply voltage to the built-in circuit, will be different when the led is on compared to when it is off.
I'm also thinking that a series led is not mandatory. The data sheet linked above (which may not be the correct one) indicates, confusingly, a forward voltage which is the same, regardless of the led colour. I suspect the built-in circuit contains a constant current driver which compensates for the different forward voltages of different colour LEDs.
Those LEDs are not blinking with a 1/12 duty cycle mentioned in the data sheet you posted. They look more like a 1/2 duty cycle to me. A 1/12 duty cycle would appear as very short blinks. The data sheet also mentions a 2.4Hz frequency, but the leds in the video have a lower frequency I think, perhaps 0.5~1Hz.
I am trying to encourage you to learn how to calculate this kind of thing for yourself, so you do not rely on others each time you have a similar question. The mathematics is not difficult. But having the correct data sheet for the components you are using is very important. I don't think we have the correct data sheet in this case because the blink duty cycle does not match.
Thank you @DVDdoug , I already connected 24 LEDs in parallel without a resistor (like in the video) and it works because the LEDs need maximum 5v and the battery can provide maximum 4.2v when it’s full. Do you think I would still need a resistor fo every LED? And if yes, what resistor would be best to use?
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