Batteries can be recharged when fully, or partially drained. Eneloop charge capacity and mAh estimates based on Panasonic internal IEC 61951-2(7.3.2) testing. Recharge cycles based on testing method established by IEC 61951-2(220.127.116.11). Solar energy charging as certified by The Green Energy Certification Center. Eneloop batteries need a charger to be recharged. Panasonic Ni-MH battery chargers are recommended. Recommended storage conditions 68 degrees F. Results may vary based on conditions of storage and use.