While this may be intentional, but I think it should be possible to use Backup Batteries while inside habitats (and pop tents in case the current behaviour applies to those too), which currently is not (the "Use" option doesn't appear at the bottom of the left panel when a battery is selected).
It can be argued that the player character is not wearing the suit while inside, however, there may be emergency situations when the suit battery should be chargeable this way, for example when running out of suit power while being in an unpowered habitat.
And while maybe I should open a new one for this as suggestion, but I think their current weight is a bit too low for a battery pack which can recharge the suit by 50%. At least 0.5-0.8, but probably more like 1 kg would likely be closer to what it should be.
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