Increase battery life and run time by using a deionizer. The use of the Deionizer System is a cost effective and easy way to purify the water used for battery watering. The simple addition of a deionizer to routine service can have a substantial impact on battery life. The Deionizer System includes an intuitive red/green color purity light to notify when the cartridge must be replaced. Impurities in the water build up over time on the plates of the battery and reduces the efficiency of the plates. Preventing these impurities from getting into the battery is the job of a deionizer. For use with Battery Filler Water Gun by Philadelphia Scientific® (sold separately).