What happens if the battery is over-discharged?

When a battery is over-discharged, the chemical reactions within the battery can become irreversible, leading to cell damage. This typically results in the battery being unable to hold a charge or work effectively. The components within the battery may degrade, which prevents it from functioning properly and can make it unable to supply power, hence it will not ignite any devices or components, including the rod referenced in the question.

Over-discharging also risks creating safety hazards, though the primary concern here is the loss of functionality. The answer indicates that in such a situation, the battery will cease to operate, emphasizing that over-discharging leads to a complete failure in the energy supply mechanisms of the battery.