Question about resistors and voltage

[jambo6984]

I want to thank everyone for helping me understand some things about this circuit here is all the information on the bulb im using
Product Name

Best Promotion High Power 1W LED Lights Lamp Bulb Diodes Chip Green Blue Warm White

Specifics
Item Type LED Bulbs
Led Bulb Type Spotlight Bulb
Number of LED Chip other
Brand Name Smuxi
Occasion living room
Beam Angle(°) 120°
Average Life (hrs) other
Color Temperature Warm White (2700-3500K)
Voltage 3.4-3.6V
Power Tolerance Other
Shape Other
Length Other
LED Chip Brand Other
Descriptions


Product Features:
1. High Power LED
2. Saving power ,Very low heat generating
3. Low consumption, high brightness
4. Special for Indoor & outdoor use, home, studio and exhibition lighting, etc.
5. Comfortable light source, harmless for skin and eyes

Specifications:
Forward Voltage: 3.4-3.6V
Color : Blue 20LM 450-460 nw
Green 70-80LM 520-530nw
Warm White 110-120LM 3000-3500K
Output power: 1W
Current:300-350mA
Light Color: Blue/Green/Warm White
View angle: 120-140 degrees
LifeSpan Time:＞100.000 hours



i ended up putting a 10 ohm resistor on the 4.2v 18650 battery my multimeter apparently cant read current so im kinda guessing but it seems like im not getting close to the brightness i could out of it, im working on getting a better multimeter, if anyone has did a similar project and could help me improve the brightness with this information that would be greatly appreciated but as of right now its atleast working and probably no chance of having to much power again i really appreciate everyones help ive read my but off all day trying to understand ohms law and circuits and i do need more hands on experience but have learned more from here than alot of the reading i do on it thanks again

 

[jambo6984]

Also im not using a heatsink should i, it doesnt get very hot as it is but if upgraded to right power im not sure thanks again i forgot to mention that in the last post.

 

[audioguru]

If the LED has a forward voltage at the minimum of 3.4V and the battery is fully charged at 4.2V then your 10 ohm resistor has 0.8V across it and limits the current to 0.8V/10 ohms= 80mA and the power in the LED is 3.4V x 80mA= 0.27W (one-quarter of its maximum power).
If the LED has a forward voltage at the maximum of 3.6V and the battery is fully charged at 4.2V then your 10 ohm resistor has 0.6V across it and limits the current to 0.6V/10 ohms= 60mA and the power in the LED is only 3.6V x 60mA= 0.22W (one-fifth of its maximum power.

For maximum power the current must be 1W/3.4V= 294mA then the resistor must be (4.2V - 3.4V)/294mA= 2.7 ohms, or the current must be 1W/3.6V= 278mA then the resistor must be (4.2V - 3.6V)/278mA= 2.16 ohms.
I think at maximum power the LED will get hot which makes its voltage drop which makes its power and heating higher, which makes more power and more heat, which makes more power and more heat, which makes more power and more heat, which ... blows up the LED (thermal runaway).

 

[KeepItSimpleStupid]

You can read current. It's just the (voltage across the 10 ohm resistor) / 10 ohms.