Tried a few more heavy workloads. Jetson keeps reporting “System throttled due to over-current.” I doubt it’s actually complaining about too much current from turning on the GPU. Most likely it’s just a standard protection error and the real problem is under voltage. The battery should easily give out 10A according to the specs and even more at peak, which should be more than enough for Jetson. The reason might be wires that are too thin and too long. I bought a barrel jack without checking the cable thickness. What arrived was AWG22, one meter long. Voltage drop on this setup can reach up to 1V during current spikes, which will definitely be noticed and probably makes Jetson do throttling even though the voltage is technically enough.
On the weekend I’ll try to measure current and voltage under different loads. In the best case I’ll just cut the wires. If that doesn’t help and the wires really are the problem, I’ll have to order a new barrel jack with AWG18 for the fourth time.