In some aspects, a method of monitoring a battery system of an industrial vehicle is disclosed. The battery system may include a first string of battery modules including at least two battery modules connected in series; a first contactor connected to a positive end of the first string of battery modules, a second contactor connector to a negative end of the first string of battery modules; a third contactor connected to the first contactor; a fourth contactor connected to the second contactor; and one or more controllers configured to monitor the first contactor and the second contactor. The method may include receiving, at the one or more controllers, an indication of a failure of one of the first contactor and the second contactor; and opening, via the one or more controllers, at least one of the third contactor or the fourth contactor.