Redundancy in battery checking behaviour

[hiradg]

In fly_bridge we currently have a global and local battery level check. The global check is ineffective since all local checks have a higher limit. I suggest we improve this by doing a voltage drop check globally and a level check locally.

[arthurrichards77]

Right - the initial use of local and global battery checks was just the best I could do with the earlier SITL stuff. If the clearance checks are in, you could just drop the "local" battery checks.

I do think there might be a case for a "low battery" local check in some missions though. It makes sense that you'd always have a "safety" level such that if the battery gets critically low, the drone gets immediately routed home. However you might also have a series of mission stages in reverse priority order, so if the battery is below a certain higher threshold, you'll skip a side-job and go straight to the most important. We don't have any examples of this yet, as so far all our contingencies have the same outcome, jumping straight to SAFTI, but this need not be the case.