ok ok....Nigel is right, it depend, if you want to feel it, take out your shoes and touch it..., Lord loh is right too, current over 10 mili amps is dangerous thru your body, most over 30 miliamps is serius and can kill a person...I been working in wet locations and 12volts batteries make me feel that flavor in the mouth that some miliamps are finding the way to ground thru me...but under high humidity...over dry conditions, 40 volts dc, will not hurt you, try not to touch negative and positive at the same time....and trust me, dc is a way more dangerous than ac power...try your finger first, but the nail side , so if you get zap your muscle will retract and you get disconected automaticly....