We do rigorous testing on not just Lithium-Ion batteries, but all batteries we sell, to ensure that you never have problems with any of our batteries. If we find a defect it the tooling process, we will stop taking orders for that battery. When it's time for a new battery, please keep in mind that Battery Universe has established a recycling program. An unproperly disposed of battery is harmful to the environment. There are many reasons why a battery will no longer work.
Some reasons depend on what type of material the battery is made from.
Sometimes older batteries don't charge in newer chargers. But most of the reasons why batteries don't work is due to improper care of the battery. The biggest killer of battery cells is heat. When a battery exceeds a certain temperature, the cells have trouble charging. Some older battery packs have temperature sensors built into the battery.