This has disturbing implications, depending on the clarification that I think is warranted (emphasis mine):
<R44> Specific items NOT allowed include:
• Batteries different from or in addition to those provided in the Kit.
We all agree on "different from", but "in addition to"? Is that meant to disallow battery farming? Can't it be reasonably assumed that there might be a lot of immovable robots (accumulating offside penalties...), due to bad design choices causing depletion of their only two legal batteries? At a small regional, where teams are sometimes only minutes removed from their last match, before having to rejoin the queuing line, that would be disastrous.
This is very much inconsistent with past practice, so I'm wondering if it's an error. Surely that's not what was intended by an "engineering trade-off".
As a note on the context, the rest of the rule also deals with no additional or different motors, and traditionally, that's to be expected. Is the same thing now required of our batteries—both quantity and type?
Edit: And this applies equally to backup and main batteries, apparently. Not much use for a backup, if you can't have another one charging.... This has to be an error.