DetailsECO Recharge is an environment-friendly recyclable and reusable batteries for your everyday needs.One single battery cell can compare to 500 of the traditional disposable alkaline batteries and those can be eliminated from going to landfills. If you buy traditional disposable batteries; it will cost you around $500 for 500 batteries; while the ECO Rechargeable batteries are the most economical and practical to use. In a 4- pack version you will prevent 2000 disposable batteries going to landfill which will also save you from buying those 2000 alkaline disposable batteries.The ECO Recharge batteries are different as they have a built-in recharge control and it will never overcharge itself. It comes with a USB cable to perform recharge; not a dedicated charger that you may be limited to where you can recharge. It works the same way all the AA and AAA batteries work. When the power is out; instead of disposing of the battereis you will just recharge and reuse.Save the environment and get the convenience of always having batteries on hand.DETAILS - 4 - Pack AA batteries with 4 plug USB charging cable to charge all 4 at the same time. 4 - Pack AAA batteries with 4 plug USB charging cable to charge all 4 at the same time. Batteries have no expiry date; they will recharge at full power up to 500 times and after that; it may continue to work but maybe at less charge.