Question

what difference is there between battery in series and parallel

Answer 1

While the voltage across each component is the same in a parallel circuit, the total voltage across each component is the sum of the voltages across the components in a series circuit. The current that flows in a parallel circuit is the total sum of the current that flows through each component whereas in a series circuit the current that flows through each component is the same. A series circuit cannot function if even one device is not working.