DELL: "unknown" state when not charging due to thresholds
Dell offers a "custom charging" mode on many laptops. It allows you to specify custom cutoffs for starting and stopping a charge to preserve battery health. For instance, you can configure it to only start charging if the charge dips below 60% and only charge up to 90%.
So far this is unrelated to upower and entirely managed through firmware and configured with UEFI setup or smbios calls.
upower doesn't correctly recognize the "plugged in, but not charging" state of this, though. In sysfs, the battery state changes to "unknown" and the charge rate (current_now) drops to 1000 µA. I think upower should be able to detect that it isn't charging. The state isn't 100% correct, but a charge rate so low is not reasonable and maybe the combination of super low charge rate plus "unknown" status should be interpreted as "not charging".