Sales of portable power supply devices that can charge smartphones and home appliances are surging as consumer awareness of disaster preparedness rises, following warnings of a possible Nankai Trough mega-quake in August and the recent landfall of Typhoon Shanshan.

Manufacturers are rushing to increase production, but some products are out of stock in stores.

Jackery, a U.S.-based major portable power supply solution firm, saw a sharp climb in sales in Japan after an alert was issued for a possible Nankai Trough quake on Aug. 8. Sales also soared after the Noto Peninsula earthquake in January, but the pace of the sales has been twofold compared to that time, according to a company spokesperson. Some popular products were temporarily out of stock at online stores and electronics retailers.