Always getting 42% battery after replacing battery

I'm getting 42% battery always. I've changed the battery and it shows still the same. After looking another source codes, they seems to read the first byte of data for this, now I get 98% after changing the pack that for it, battery, firmware = unpack('<xB5s', data) to battery, firmware = unpack('<Bx5s', data) - but I cannot ensure its ok. Time will show if it is. Firmware version: 3.2.1