Having the battery and brake light on at the same time suggests you have a dead alternator. When the alternator can’t providing the power needed to supply your car’s electrical systems, it leads to faults and irregularities in these systems, including your brake sensors and ABS system. It could also be another electrical fault, like a bad voltage regulator or a loose battery connection. Of course, you could just be unlucky, and have separate issues pop up at the same time.
