The /EOSC bit should be set to 0 so that the internal oscillator remains ‘on’ while on battery power. This should be the default value on first power on. If /EOSC is set to a bit value of 1, then the oscillator will be halted when operating on battery power, which is not what you want.
So keep /EOSC set to 0 at all times. There is no need to ever change this value to 1.