To determine if your lithium-ion battery is bad or damaged, watch out for the following signs: reduced capacity, shorter battery life, overheating, swelling, physical damage, inconsistent performance, sudden drop in charge percentage, and failure to charge.  If you notice any of these signs, it's best to stop using the battery and seek professional help or replace it with a new one. Damaged or faulty lithium-ion batteries can pose safety risks, including the risk of fire or explosion, so it's essential to handle them with caution and ensure proper disposal or recycling.