Adam takes on a bit of shop infrastructure this week to tackle the inefficiencies of lithium-ion battery chargers. Specifically, he needs a charging rack that can store, charge, and organize the cave's set of 3.7V li-ion cells--the kind used for high-powered flashlights and other electronics. Adam builds a portable gang charger that can power eight batteries at once from a single power supply--a simple build you can do at home too!