You can check to see if your battery is sulfated in one of two ways. If you’re noticing signs of decreased battery efficiency — like a battery that’s not charging as well as it once did or one that isn’t charging at all — you likely have lead sulfate crystals present. Batteries that won’t hold a charge and electronics that aren’t functioning properly, like weak AC or dimming headlights, can also be signs. Or, you can take a look under the hood and check your battery for visible signs of sulfation. You’ll have to open your battery up, but if you see gray, grimy, and not-so-clean lead cells inside your battery, that’s sulfation.