A rechargeable power source, which is detachably coupled with a shading device to electrically connect with an electrical arrangement thereof, includes a rechargeable battery unit having a battery terminal arranged to contact with the electrical terminal of the electrical arrangement, and a locking arrangement which contains a releasable locker to detachably couple the rechargeable battery unit with the shading device and to ensure the battery terminal being contact with an electrical terminal of the electrical arrangement so as to electrically connect the rechargeable battery unit with the electrical arrangement. Therefore, the electrical arrangement of the shading device is powered by the rechargeable battery unit to eliminate the power extension to the external power source.