My batteries that I replaced from the unit were green "Suppo HSY-AAAD 75-PHP NiMh 750mAh 1211". I replaced them with some typical "Energizer Recharge Power Plus 700mah Rechargeable Batteries" that i bought from Amazon. I wasn't gentle with replacing the batteries. I literally ripped off the metal connectors and wires and taped them back on the net batteries in the same configuration as the original batteries. The enclosure it tight enough so that the connectors will stay in place without soldering. I also noticed that there is a tiny on-board LED which blinks 8 times once you properly connect the batteries in place. It's analogous to the orange device light that blinks 8 times when the device needs to be recharged.