thank you all for your answers, but I think you did not understand me, let me explain, I have a lighting lamp that works, and I want to extend the lighting time each time the battery is recharged , example if the current lighting duration of my lamp is 6 hours, how can I increase it

measure  signal to lamp with scope, then look for filter to flatten and widen spike

You might try a suitable PWM controller.

thank you all for your answers, can someone help me to work on this project
best regards STI

I thought you already had build a joule thief 
start here and replicate the minimalist fleet joule thief https://www.researchgate.net/publication/358710193_Practical_Guide_to_%27Free-Energy%27_Devices_Version_348