12v->5v inverter sounds odd?

[Invictus3593]

Our power inverter for the d-link emits this quiet, high-pitched, dog-whistle-type noise each time we try to power it from it's own special 12v connector on the end of the PD board. When we plug it into a normal, 20-amp line, however, it's totally silent. But, because we're powering it from the normal PD board slots, it reboots every time we pull too much from the battery, causing us to lose comms and sanity.

Any ideas on how to fix this? Should we try a different inverter? We're using a brand new PD board and new inverter, but we need to get this fixed because we don't want our radio rebooting every time we start a match.