Energy Storage Module
The Energy Storage Module is a block that can store 2.5 Mega Joules(MJ) of energy [in Galacticraft 3: 500,000 gJ] for later use. It was added in Galacticraft 2 and replaced the Battery Box from Basic Components. When the block is broken, all the stored energy held inside is lost.
Using Aluminum Wire connect a power source such as a Coal Generator to the green input side. Then connect the red output side to the machine requiring energy. If no energy is being consumed by a machine or if excess energy is being produced, the module will slowly charge up. When energy is no longer being produced or if the demand from the machine(s) is too great, the stored energy will slowly deplete until a sufficient power supply is present again.
It is especially useful with Solar Panels: the Energy Storage Module charges up during the day while the sun is shining, and discharges at night. More than one Energy Storage Module may be needed for continuous power, depending on the requirements of your base.
Energy Storage Modules can charge any electrical item placed in the charging slot. The basic version of the Energy Storage Module may have limited power for charging items if its standard output is already being used at full capacity. When upgraded to an Energy Storage Cluster it does not have this limitation, and can charge electrical items much faster.
A charged Battery (in Galacticraft 3, including batteries from most other mods) can be placed in the bottom slot to expand the amount of energy available. However if the Energy Storage Module and the battery are both discharged, then that battery will not recharge in the bottom slot. It would be possible to charge an additional Battery in the top slot and using these two slots, you can effectively have a higher capacity Energy Storage Module, but it will require some micro-management switching the batteries from the bottom slot to the top and vice versa once charged.
Note As of Galacticraft 3 release, your batteries must not have any charge, else the recipe won't work