Why does the red light flash when Sony camera is charging?

"The red light on the charger is flashing all the time" is a hint: the battery is in poor contact with the charger. Metal points in the charger box that are in contact with the battery and metal points on the battery may be oxidized in the air. Just scrape it with a tool and polish it. In addition, my personal experience is to put a thick piece of paper on one end of the battery to make the contact end of the battery and charger closer. When the discharger enters the charger, try several more positions. Whether the red light flashes or not indicates normal charging.