18650-type Li-ion batteries are a great source of energy, but if you need a voltage higher than, say, 3.6 to 3.7 V (the nominal voltage of a single cell), then things can become a bit more challenging. Adding an inexpensive step-up or booster module is a possible approach. If, however, the goal is a low-noise power source, then the best solution would probably be putting two or more batteries in series. But then how do you charge them?