It is really sad if you are covering special events like a wedding, and then suddenly, your camera’s external flash would run out of battery. When you don’t have extra battery to use, it is better invest in a chargeable battery than to be in a position like this. If there’s an available eneloops from thomasdistributing then the better. According to my husband, using eneloops during my sister’s wedding celebration enabled usage of more than 300 shoots without a miss.