Good night everybody. I´m using the audiomoths for recording bats and I need more work time, because with only 3 AA batery is not enought. Well, i read that the device can work betwen 3.4 and 20v (DC). I put four 18650 batery, whit an initial voltage around the 16.4v. (the teorical voltage is 3.3v x 4, but the real voltage is biger than this voltage) Well, the device works, but i feel some heat in the power input, so i think if it spend some energy in heat, it will have less efficiency and maybe be better to conect all the batterys in parallel, with 3.7v in the begining... What do you think about? Note, i will use 512 Gb cards, i would like complete de card.