An energy storage unit with capacity determined by the battery/crystal items placed in it.
In my perusal and brutalizing editing of the wiki, I came across the MFSU page and noted, with some dismay, the line: 'This is the only storage unit, out of 4, that stores less energy than the sum of its component [sic] does.' (Which is true - 40M for the MFSU vs 64M from 6 lapotron crystals and the MFE.) So I thought about that, and a fittingly IC2 sort of way to address the issue, and came up with the idea of the EESA, or Expandable Energy Storage Array.
Long story short, it's a box with some number of slots in it, in a grid - maybe 3x3 or 4x2 or 4x4, it doesn't matter as far as the concept is concerned - into which you place RE Batteries, Advanced RE Batteries, Energy Crystals, or Lapotron Crystals (or maybe something else, like the charging versions). Essentially, the box would wire them in series and act as one giant energy storage box, discharging and recharging the individual items instead of a single internal reservoir as in the current EU storage blocks. Thus, you could expand your storage a little more gradually as you acquired the resources to do so. I've been doing some research on batteries and what might make sense somewhere between IC2 and reality, and this is what I came up with.
A few options (I love giving options, it makes my weird ideas easier to stomach):
- Have a single reservoir, but just adjust its size dynamically based on what items are installed instead of actually charging/discharging the actual items (not sure /quite/ how this would be coded though)
- Make the user fill every slot; if there's no battery, it has to be occupied with a cable or something (for electrical connectivity, see) or the block won't accept input or give output
- For voltage: either have another slot that determines output voltage, which accepts an LV/MV/HV/EV transformer, or have the EESA shapeless-craftable with those to set its voltage (so it'd have no output initially, and you'd also have to empty it and wrench it out to change the voltage). I tend to favor the former, but that's me.
- Limit the input items to the tier of the EESA itself (admittedly this is probably easier if it's crafted with a transformer to set its voltage? but what do I know about code)
- Alternately, have different tiers of EESA where each is used to craft the next one, so there's more of a sense of progression (the only progression now is MFE -> MFSU, the batbox and CESU are pretty worthless once you have a few transformer upgrades and don't need the batbox for a jetpack)
- Even more alternately, make the EESA EV(+IV?) only, which would limit it to being simply an expandable high-tier storage device.
- A slightly odder idea: add storage space in the form of connected blocks, a la reactor chambers for the nuclear reactor, to expand the EESA's available slots. Make a /really/ big series-battery.