Six 18650 Batteries Tested: Smart Charger Versus Choice... Surprising Insights When Compared! Among the batteries we tested, the 6pcs 18650 Rechargeable Battery set stood out for its convenience. The included smart charger is Universal Smart, effortlessly handling 3.7V lithium-ion batteries—no need to guess compatibility. We appreciated how it charges six batteries efficiently, with clear LED indicators for each cell. However, the button-top design felt slightly outdated compared to newer models. The overall build quality was solid, though the case durability left something to be desired. Our only surprise was the charger’s inconsistent performance with older batteries, while new ones charged flawlessly. While the kit offers value for enthusiasts, we recommend budgeting extra for compatible, higher-capacity cells. The smart charger works great—but not all 18650 batteries are created equal.