You'll want to make your way over to caravan town, which is actually a goldmine for battery-related stuff (this is because it's a major story location with lots of tech). While you're there, check around the dock area and keep an eye out for those battery charger pieces - they're pretty obvious once you know what to look for. There's this interesting well puzzle you'll need to solve, which involves rotating water pipes to get things flowing properly.

Getting started with batteries is easier than you might think, since you can research the basic ones at your table using materials you've probably already collected from islands. Once you've got the hang of that, you'll want to focus on building the battery charger, which needs some specific materials like circuit boards and titanium (i'd recommend stockpiling these ahead of time).

Something that's really helpful to know is that there are quite a few machines you can power with these batteries, each serving a different purpose. The electric grill makes cooking way faster than the basic one, and the electric smelter is fantastic for processing metals quickly - which actually helps you create more advanced stuff down the line. The juicer might seem less important, but those beverages can be really useful for longer exploration trips.

When you're searching for parts, always take some extra time to thoroughly check around docks and buildings, since the developers tend to hide components in these areas (this is actually a common pattern throughout the game). Remember that puzzle areas often hide the best rewards, so don't rush through them too quickly.