We recommend using a rechargeable 12 Volt battery. Amp hours (Ah) should be 4.5 or more. In our own complete feeders we use a marine/leisure battery of 75 Ah connected to FeedCon.
The NG CF 250 liter feeder can accommodate a battery up to 41 x 19 x 22 cm (WxDxH)
The NG CF 500/1000 liter feeder can accommodate a battery up to 27 x 28 x 25 cm (WxDxH)