Whether a solar battery is a worthwhile, beneficial additional to your solar system depends on your electricity usage patterns and what you want to achieve.
Solar system costs have become very much competitive throughout India. The cost of adding batteries to the solar system is completely depending on the size of storage you need to install.
The cost ranges from Rs.5000/- to Rs.7000/- per kWh capacity of the batteries.
You could also be eligible for cost saving incentives from your state or central government, most solar batteries are warranted for at least 5-6 years.
Then all you need is an installer you trust to properly integrate the system into your current solar setup.