Note:21.9V is Pool Cleaner's battery voltage. NOT charger's voltage. Please Check For Compatibility With Your Unit. Thanks. Compatible with: Smonet Model CR6 Pro CR6Pro Cordless Robotic Pool Cleaner Power Supply; Note: Rechargeable batteries typically last 1 to 3 years. If a battery is old or depleted,it may not charge,but this isn't necessarily the charger's fault. To determine if the charger is working,use a voltmeter. Compatible with listing item ASIN: B0CWGKM21N - Compatible with SMONET Cordless Pool Vacuum Robot: Automatic Robotic Pool Cleaner Lasts 150 Mins Wall Climbing 180W Powerful Suction LED Indicator Self-Parking for Above Ground & Inground Pools Up to 2,000 sq. ft. Compatible with listing item ASIN: B0D17HGZG4 - Compatible with SMONET Cordless Robotic Pool Cleaner: Automatic Pool Vacuum Robot Lasts 150 Mins Wall Climbing 180W Powerful Suction LED Indicator Self-Parking for Swimming Pools Up to 2,000 sq. ft. Grey saschedross AC Adapter Replacement For Smonet CR6 Pro CR6Pro 21.9V 7800mAh Li-ion Battery SAT-3P6S 180Wless Robotic Automatic Wall Climbing Pool Vacuum Cleaner Power Supply Mains PSU