Why is my battery bulging?

What is my battery swollen and smell like rotten eggs?

This is likely due to a "thermal runaway" event. The battery (or batteries) should be replaced. Before charging the new batteries, confirm that the charger settings are correct when applicable. The charger should be set for AGM type batteries. The charge current should be set to no more than: 25A for a single 100Ah battery 50A for a two 100Ah batteries 75A for a three 100Ah batteries