Ryobi Battery Charger Sensor Holder for 75% Storage Charge

This device fits certain Ryobi 40 volt batteries. Its purpose is to hold a light sensor that will turn off your charger once the battery has reached 75% of full charge. Ryobi advises that you will harm your batteries if you leave them at 100% charge for long term storage. They consider long term to be 30 days or more.

Ryobi advises an 80% charge for long term storage. See How I Designed This for more details.