Not true. They have an internal battery which holds TC for at least 10 minutes. Rado, you must have been on the wrong battery chemistry in the SYS menu setting. Also, their battery telemetry is extremely accurate. I monitor all the slates and lockits via the Tonmeister App connected to my Master Lockit. You can choose the battery chemistry (Alkaline, Lithium, or NiMH) and all are amazingly precise. The slates stay on for about 10-20 minutes past the 0% indicator, which I find very helpful. Full use of the battery scale makes the entire scale more accurate and meaningful. I can only imagine having slates that are exactly frame accurate all day, from start to finish, is a huge asset to our telecine (Dailies) technicians. So far the feedback is "It works!". As Eric stated, NiMH rechargeables easily last a long day. After 14 hours, the slates typically indicate 30% charge or better. Last few days in the Georgian summer heat, the NiMH have reported better than advertised voltage. The slates therefore indicate Ext Power or periodically fluctuate 40% up or down. I blame the heat index of 112, and an uncharacteristically high voltage from the cells. And the display rotating to the correct orientation when they hit tailsticks is super cool.