There are a few common symptoms of batter failure these are: A. Unable to start your lawnmower engine (This means when you Turn ON the key switch and try to turn it ON your lawnmower won’t start which means that your battery might not work properly). B. Surging (Sometimes your lawnmower starts and then turns OFF, you turn it ON again and when starts working it loses power, in some cases your battery is working but not generating the full voltages so you face problems. In this condition, you check the liquid level in your battery. C. Corrosion (If there is corrosion, carbon, and dirt on your battery surfaces it means your battery does not work properly and you might face problems to avoid this problem you clean your battery after some time as I mentioned cleaning method above paragraphs). D. Not holding the charge ( Lot of user face problems with their batteries that do not hold the charge, the battery is fully charged but when used it drained too early and not working every for a short time. That means your battery is completely defective you may change the plates of your battery or buy a new battery. These are the major symptoms of a defective battery. Most of the people are complaining about the battery and told these symptoms.