Batteries are one of the types of Items in Astroneer which store power. When a surplus of energy is produced, it is used to fill a battery somewhere in the network (assuming all modules' internal batteries are full.) They can be filled or depleted at a maximum rate of 4 units/sec (or 1 bar/sec).
This page is about the external batteries; see the Power page for the differences between the internal and external batteries.
Crafted from the Backpack
→ See Small Battery
The 2-bar external battery on the right side of the backpack, below the oxygen tank.
After completing the necessary research, you can craft a small battery in your backpack's printer using 1 Lithium.
You can attach it to any attachment point on your backpack or base, including the backpack's widget slots. It stores up to 8 units (or 2 bars) of power.
When placed in the backpack, it increases the total energy storage by 80%, from 10 to 18 units. Energy will be drawn first from the crafted battery over the internal battery, but, as said above, will only be filled when the main battery is full.
Crafted from the Printer
→ See Battery
The 16-bar battery
You can craft a larger battery in the Printer module for two Lithium after completing the necessary research. As it is a medium-tier module, you can place it in any two adjacent slots.
It stores up to 16 bars of powers.