Battery Replacement Voltage

May 19, 2018
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I have a Dell Inspiron 3521 and I am in need of a new battery. The stock Dell battery is a 40WH battery rated at 14.8V. If I were to buy a replacement battery at 48WH and rated at 11.1V, would my battery life increase and decrease?
I need a bigger battery so I was also wondering if anyone new any good replacement batteries that could give some extra battery life?