Every battery manufacturer offers a limited warranty on their products, ranging from 36 months to 5 years. There are three types of warranty schemes.
The first one is a free replacement warranty, wherein you get a new battery at no extra cost if your battery fails within the warranty period.
The second one is a pro-rata warranty, wherein you get a big discount on the new battery if your existing battery fails within the warranty period.
The third type is the composite warranty, a combination of free replacement and pro-rata warranty. For instance, a battery manufacturer may provide a comprehensive warranty of 48 months. Out of those 48 months, the first 24 months may be covered under a free replacement warranty, and the remaining 24 months may be covered under a pro-rata warranty.