So, in review, wiring lithium batteries in series is just as simple as wiring lithium cells in series. The difference is that lithium batteries have a BMS which contains MOSFETs that might not be able to handle the higher voltage that they would experience when one battery dies.
Connecting battery cells in series is a pretty straightforward process, but there are some key elements that should be understood before doing so. To connect lithium-ion batteries in series, all you have to do is connect the positive connection of the first cell to the negative connection of the next one.
You should connect lithium batteries in series when your device requires a higher voltage than a single battery can provide. For example, if your device operates at 7.4V, connecting two 3.7V batteries in series would be appropriate. This setup is commonly used in applications like electric scooters, drones, or other high-voltage devices.
Adding battery cells in series adds their voltages together while not changing the amp hours. It’s important to consider, however, that because power is a measure of volts multiplied by amp hours, putting lithium batteries in series increases the overall power by increasing the overall voltage.
Charging lithium battery cells while they are in a series configuration is not only possible but very common. It’s how ebike, laptops, and just about any other battery chargers work. When charging lithium batteries in series, the charge voltage is divided among the number of cells in series.
Either way, once you wire a set of lithium-ion batteries in series, it will form an open-ended chain. At the ends of the chain, you will find your main negative and positive connections. When battery cells are wired in series, their voltages are added but their amp hours are not.