When this happens, you should totally desulfate the battery to ensure that it again holds a charge. Desulfation is additionally called battery "reconditioning." Since batteries include toxic chemicals, such as lead acid, you have to take safety and security precautions. Always put on safety glasses and gloves when performing this https://howtorestoreacarbatterywi62737.tinyblogging.com/h1-evaluation-ez-battery-reconditioning-does-it-function-or-otherwise-h1-78849354