A battery renewing device is a tool that is used to restore old or faulty batteries back to their original performance. There are many different synonyms for this term, such as battery rejuvenator, battery recovery machine, battery desulfator, and battery regenerator. A battery rejuvenator works by removing sulfation, which is a buildup of lead sulfate crystals that can decrease a battery's performance over time. The battery recovery machine works by charging and discharging the battery in a particular way, allowing it to restore its original capacity. The battery desulfator and battery regenerator, on the other hand, use specific chemicals to remove the buildup of sulfation. Regardless of which tool you choose, these devices help extend the lifespan and improve the performance of your batteries.