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You cite the voltage drop across the LEDs as 3v. This would limit you to running 2 of them from a 9v battery (as a rule of thumb, you don't want the total voltage drop to exceed 2/3 of your supply voltage), unless you include a voltage booster circuit.

Also, speaking generally, you may want to consider a current-limiting resistor (unless the ones you're using have one built in -- most LEDs don't). The formula to determine the value of it in ohms is (Vs - Vf) / I, where Vs is the supply voltage, Vf is the voltage drop (summed if you wire them in series, but your image shows 4 in parallel -- and are those 4 banks wired in series? If so, then you're looking at about 9Vf), and I is the maximum current the LED bank can handle (in amps). If you're wiring all 4 banks, I'd probably include a limiting resister for each bank, and it would be the sum of the max current each LED can handle, which would be 80mA per bank).

For example, for a single 3v, 20ma LED running from a 9V battery, the resistor needed would be (9-3)/0.02, or 300 ohms.

You cite the voltage drop across the LEDs as 3v. This would limit you to running 2 of them from a 9v battery (as a rule of thumb, you don't want the total voltage drop to exceed 2/3 of your supply voltage), unless you include a voltage booster circuit.

Also, speaking generally, you may want to consider a current-limiting resistor (unless the ones you're using have one built in -- most LEDs don't). The formula to determine the value of it in ohms is (Vs - Vf) / I, where Vs is the supply voltage, Vf is the voltage drop (summed if you wire them in series, but your image shows 4 in parallel -- and are those 4 banks wired in series? If so, then you're looking at about 9Vf), and I is the maximum current the LED bank can handle (in amps). If you're wiring all 4 banks, I'd probably include a limiting resister for each bank, and it would be the sum of the max current each LED can handle, which would be 80mA per bank).

For example, for a single 3v, 20ma LED running from a 9V battery, the resistor needed would be (9-3)/0.02, or 300 ohms.