I have a problem with bios backup (power status inadeqate)

I try to make bios backup with usb disc but always when I try this i see bios backup site  with information power status inadeqate I exchange battery and have oryginal charger maybe this error will be for low power od cmos battery because I check voltage and in oryginal  battery could have voltage 3V but when I check battery has only 2V.At first laptop lights inform 3 times amber and 3 times white and after this 4 times fast amber and one white.Battery won't be charge when I use charger.