The Range module provides a destination handler which exposes range fields for mapping.

Range field requires both FROM and TO values, so it doesn't make sense to use the primary value, i.e. map to field itself.
In order to use it, please map values to the subfields (mapping to the field won't work)

Fields

from - Range field FROM value
to - Range field TO value
language - Range field value language

Example

// Correct way: map to subfields.
$this->addFieldMapping('field_range:from', 'range_from');
$this->addFieldMapping('field_range:to', 'range_to');

// Incorrect way: map to the field itself.
$this->addFieldMapping('field_range', 'range');