Hello Slavixs
I've tried to change battery. I don't know if the technical service I contact was lack of knowledge regarding this device, but battery was removed and changed with no result. The technician said there is a problem with this microcircuit that can not be replaced so now I have a useless device what is a real pity because there is no support after all.
My suggestion is to be extremely careful with this device, if you change the battery and there is no result (by the way you can use any cellphone battery) it is supposed there is a problem with circuit.
Kind regards.