Instead of one super chunky battery, how about a laptop with replaceable batteries, in combination with a UPS?
UPS is so you can actually replace the laptop battery with a spare one , even during a power outage. Just run the laptop on AC from the UPS while changing batteries. Or see if you can find a UPS with a long lasting battery. Entry level ones only have like 15-30 minutes of battery life though, since they’re more intended for safe shutdowns or brownouts.
This happens when a small project has 12 developers each scratching their own itch in their own time, not a team of 120 developers getting paid to work on the same itch 8 hours a day.
In the case of FreeCAD they’re actually starting to reign in and focus more now, and there are more contributors.