[codedr]

+1 Everything Al said.

In every case of brownouts I investigated at champs, 100% of the time there was at least one of (A) loose battery cable, (B) loose connection at breaker, or (C) loose connection into the power distribution board.

If you can move the battery cable up and down, the bolt isn't tight.
If you can move the cable back and forth at the breaker, the bolt isn't tight.
If you can move the cable back and forth at the PDP, the bolt isn't tight.

The PDP connector is harder to reach because the covers.