if you have a mod that runs on the 18650 madvapes has the nimh 4.8 volt battery that fits, only thing is it's a flat topper, no nub. same vapor with only a little puff rather than a deep draw, an old atty at 4.8 is like a new one at 3.7 for me. or, you can double stack 3 volters and regulate it down. i originally wanted to do that but when i shoved/crammed the assembly down my tube i kept breaking the connections, so i just simple switched it and decided to do my voltages with batteries (single for 3.7, double for 6.0, nimh for 4.8, etc).