this is specification of one Integrated Solar Panel Street Led (all in one )

how i know watt of LED instead of LED lumens ? and is 3.7v good?? or 12v is better ?

http://www7.0zz0.com/2016/09/30/11/326553627.jpg

 

Watts is not a photometric measure of light output.

The battery voltage is irrelevant.

Lumens is what is important, it's how you actually measure a lamps optical output power.

 

This table from Wikipedia gives an approximation based on minimum assumed efficiencies. As mentioned, converting watts to lumens includes an efficiency term for light fixtures.



John