Battery holder and mobile illumination device using same

A cell holder with a compartment for accommodating a button cell, wherein:

• the compartment is a casing including four lateral sides, an upper side, and a lower side,
• the four lateral sides includes:
• a first lateral side having an opening side through which the button cell is loaded or ejected from a side surface of the button cell,
• a second lateral side opposite to the first lateral side, and
• third and fourth lateral sides perpendicular to the first and second lateral sides,
• the compartment includes an elastic piece for biasing at least one of flat surfaces or the side surface of the button cell,
• a slit is disposed on at least one of the upper side and the lower side,
• the slit extends from the second lateral side toward the first lateral side, and extends to a part of the button cell,
• the slit includes an end positioned closer to the first lateral side, and has a long narrow rectangular shape in plan view, and the slit has a width of less than 5.6 mm, and
• the end of the slit is positioned closer to the second lateral side than the biasing portion where the elastic piece biases the button cell.