# Drive a 3w led with a 18650 li-on battery

I'm getting crazy trying to figure out if there is any easy way to power up a SINGLE 3w led
3w - Forward Voltage: DC 3.2-3.4V - Forward Current: 500-700mA

with a single 18650 li-on battery

Minimum Capacity: 2250mAh (0.54A discharge at 20°C)
Typical Capacity: 2100mAh (0.54A discharge at 20°C)
Nominal Voltage: 3.6V
Discharge End Voltage: 2.5V
Standard Charging Current: 1.1A
Charging Voltage: 4.20±0.03V
Standard Charging Time: 4.0hours
Max. Continuous Discharging Current: 2.2A
Internal Resistance: less than 35mΩ
Weight: less than 47.0g


Is there anyway to do it without using a dc-dc buck converter? I'm trying to change a led on a torch, so I have not so much space to work in.

Thanks

• can you make a heatsink? – Sunnyskyguy EE75 Jan 4 at 18:51
• Is it a single led or a string? – Satish Singupuram Jan 4 at 18:54
• It's a single 3w led, and I have already a small heatsink on the torch, and one pcb heatsink on the led – mosfettis Jan 4 at 19:00
• You can achieve that by using a simple current limit resistor of require wattage between battery and led, but the brightness of the led will decay with the voltage of battery and you cannot use the battery to its maximum capacity... is it ok? – Satish Singupuram Jan 4 at 19:03
• I already tried with 1ohm, 1,2 ohm, but the led is not powering up. Am I doing wrong calculations? – mosfettis Jan 4 at 19:06