The battery pack belongs to the vehicle, not to a constant

[yalexx]

A --model json SITL takes its battery from the simulator: ArduPilot's JSON backend reads voltage and current out of the physics frame every tick, so the autopilot's own SIM_BATT_* parameters have no effect on what it believes about its pack.

skysim was therefore the only thing deciding endurance, and it decided the same thing for every vehicle in every world — a 3S 3.3 Ah hobby pack, 12.6 V full, compiled in.

That is roughly a fifth of the aircraft the SkyHub fleet stands in for, and it was invisible from the caller's side: the gateway set SIM_BATT_CAP_AH to 27 Ah, read it back as 27 Ah, and watched the vehicle reach its reserve in six minutes. Three full survey runs were measured against the wrong aircraft before anyone thought to look at the pack voltage — 12.59 V on what was supposed to be a 25.2 V battery.

What changes

The pack moves onto SpawnRequest as a BatteryPack (capacity, full/empty voltage, idle and draw current), so a caller can describe the aircraft it is simulating, and a world can hold a mixed fleet.

Defaults are the old constants, so a spawn that says nothing about its battery behaves exactly as before.

A pack whose empty voltage is not below its full voltage is corrected rather than accepted — inverted sag would make a draining battery report a rising charge, which is worse than refusing the request.

battery/reset now restores that vehicle's own full voltage rather than a compiled-in one.

A note on the field name

hover_a is not the current at hover; it multiplies the square of normalised throttle. Reading it as amps-at-hover is about a factor-of-ten error, and calibrating against an assumed cruise demand rather than a measured one has now gone wrong twice downstream. Worth renaming at some point.

Testing

All 11 test binaries pass. test_api covers the defaults, a fully-specified pack reaching the tick thread, and the inverted-voltage correction.

🤖 Generated with Claude Code

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Reviewing files that changed from the base of the PR and between 8251bc2 and 89a9f15.

📒 Files selected for processing (4)

• src/api/control_server.cpp
• src/main.cpp
• src/vehicle/manager.h
• tests/test_api.cpp

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