How many LEDs can a 9 volt battery power in parallel?

Basically what the title says 

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PratyushJ9 months ago

One 9V battery will give you somewhere between 120 and 200 hours of illumination with the simplest circuit, a series resistor. With a good switching voltage converter circuit you should be able to get more than 600 hours.

lemonie8 years ago
What sort of LED, which 9V battery?
You could run quite a lot at low current with a good battery.

If only for a short time a 9-volt can put out full amps at completely short circuit.

Agreed - quite a few.

As for how many - it would make a lot of sense to run series strings of 2-4 leds to better utilize the whole 9 volts and put THOSE in parallel with each other.
Zem (author)  frollard8 years ago
I've heard of that before, but I don't exactely understand how to do that? 
frollard Zem8 years ago
Use  this calculator

Each led has a forward voltage.  2 leds in series uses 2 times this voltage...etc.

each led has a CURRENT.  2 leds in PARALLEL use 2 times this current. et al.

9 volts is way more than 1 led needs, and you'd need a resistor to burn off the excess.  If oyu have 3 volt leds, you could put 3 in series and use a VERY small resistor to prevent overcurrenting the leds.
Zem (author)  frollard8 years ago
The link you gave me doesn't work =/ got any others?Okay! Thanks!! 
frollard Zem8 years ago
always works!  

tell it 9 volts source
3 volt leds
20 miliamps each
and total # of leds you wish.
Zem (author)  frollard8 years ago
Awesome! Thanks! 
frollard Zem8 years ago

remove the &nsbp from the end.
Zem (author)  frollard8 years ago
Okay! Thanks!! 
Zem (author)  Zem8 years ago
Zem (author)  lemonie8 years ago
Blue or red LEDs, and a Panasonic 9v. 
frollard Zem8 years ago
red leds are 2-3 volts, blue are 3.5.

Check the exact specifications on the packaging or model number.
Best answers can't be awarded on replies, but you've got it in theory...

Zem (author) 8 years ago
Thanks everyone!