the current market for solar lamps is very chaotic, power exaggerated seriously, Some are dozens or even hundreds of false markers, In fact, the user is ultimately concerned about whether the lamps are bright enough, Is it lighting time long enough, The most direct parameter is the power of the LED chips, the power of LED chips P=I( current)* V( voltage); if the power of the LED light source is 30W, assume 4 strings of 32650 lithium batteries used, the voltage of battery is 12.8V, The current of LED light source is 30÷12.8≈2.34 A, suppose it Lights up 8 hours per day, and It is sunny every day (no rainy days) always, The lamp efficiency colligating the controller, wire loss and battery discharge depth etc. is less than 0.8, so the minimum required capacity of the battery is :2.34÷0.8=23.4 AH, If you want to make sure the lamp is still work after a rainy day, The capacity must be double, says 46.8 AH, or Simply understanding we need 32 pieces A grade 32650(6AH/3.2V) lithium batteries;