Will I need to replace the battery soon, and what does a replacement cost in India?

You may not need to replace the battery soon, and if you do, it is usually an inexpensive fix. A certified refurbished laptop has its battery health checked before sale, so it should give you good everyday backup from day one; the battery then ages gradually, like on any laptop. If a replacement is eventually needed, most refurbished business laptops (ThinkPad, Latitude, EliteBook) use widely available, easy-to-replace batteries, and a replacement typically costs in the low thousands of rupees depending on the model. That is far cheaper than replacing the whole laptop, and is one reason business-grade refurbished machines stay economical for years. Note that the battery is treated as a consumable, so it is not covered by the standard hardware warranty unless it fails due to a manufacturing defect. Check battery health on arrival within your return window, and budget for an eventual low-cost battery swap rather than worrying about it upfront.