Here is a video that may help. I made my battery packs 3S. So have 2 packs wired in series 19.8 volts of power. I can't recall if I made the Y harness or purchased it. I have the standard Life battery charger. It only charges a 3S pack at a time. But not a problem, it just takes a bit longer to charge. Basic old technology, just charge and use. I put a short balance plug on the battery packs. But I also made a longer balance extension to connect battery pack to the charger. Works good. I use the extension for the airplanes too as the battery pack is usually buried in the plane.