Hi ive just bought a brand new green laser pointer from China three days ago and it costs roughly about USD$25 and i have just used it today , i tried placing my previously bought 4.2V Ultrafire Li-ion batteries and no light came out of the laser. But it was working fine before changed the batteries. But however when i put my Ultrafire 3.7V(came with the laser) , the laser suddenly does not work. My surrounding temperature is around 30degrees celsius . May i know if the problem is caused by my batteries or wasi just unlucky to buy a faulty laser? By the way it says 200mW on the sticker, not sure if its real. Would appreciate some advice.