Portable power supply

A portable power supply comprising:

• a housing defining a cavity, the housing including
• an upper portion,
• a lower portion,
• a plurality of air inlets defined in the lower portion, the plurality of air inlets in fluid communication with the cavity, and
• a plurality of air outlets defined in the upper portion, the plurality of air outlets in fluid communication with the cavity;
• at least one battery cell disposed in the cavity;
• a charger electrically coupled with the battery cell;
• an attachment coupled to the upper portion by a plurality of fasteners, the attachment configured to at least partially cover each of the air outlets such that airflow exiting the air outlets travels a circuitous path, the attachment including a first side facing the upper portion and a second side opposite the first side,
• the second side including a coupling interface, the attachment 50 configured to supply power to the coupling interface, the coupling interface is configured to engage a stacking interface of a chargeable structure.