1 18350 or 18650 has a max voltage of 4.2v. By stacking, you are doubling the voltage, so... if you are vaping at say 4.8v, the vamo has to boost that 4.2v battery up to 4.8, with stacked batts, you would have 8.4v, so instead of the vamo having to boost the power, it can scale it down, which...