Hi. I'm getting this error when trying to run your mod:

Error ModManager.cpp:1577: Error in assignID: entity with name 'bp-holmium-battery-charger' does not exist.

Source: bp-battery-charger (furnace).

And you mentioned that higher tier batteries are only available with SE. It would be nice if there's another way to obtain them on non SE runs. Maybe make their recipes expensive or make them use higher tier items?

The bug was related to the settings for the upgrade planner. Forgot to omit them when there actually is nothing to upgrade to.

My thought regarding battery tiers was that a much less resource intensive equivalent for solid fuel would be enough for vanilla. There's also the issue of upcycling to the next tier of batteries. SE has a recycler building to get some ingredients back from the obsolete tiers. In vanilla they would just waste storage space somewhere.

Thank you for fixing the error.

I wanted other tiers because rampant and bob's energy weapons eat energy like candy and your batteries were perfect for supplying energy to far outposts. I don't mind leftovers as they can be destroyed in an incinerator mod. But if you think it breaks the balance somehow then no worries. Nonetheless great mod and nice looking sprites.