RECHARGEABLE UP TO 500 CYCLES: Every 4Patriots USB Battery is rechargeable up to 500 cycles. Drain down the 3,800 mAh lithium polymer battery & charge it up with any USB port. Your batteries will "fast charge" in as little as 5 hours depending on charging conditions!.IDEAL FOR: Anywhere you use a regular D battery! Flashlights, radios, fans & more. With your 2 USB-Rechargeable D Batteries, you'll have long-lasting & durable power for everyday items. Or you can stash them away with the included clamshell case. Simply top them off every 3-5 months to keep them fully charged..ESTIMATED COST SAVINGS: Since each battery recharges up to 500 cycles, it's like you're getting 1,000 batteries! That's a savings of $15.92 versus the 3 leading traditional D battery brands! That makes them climate friendly & a great source of green energy. Plus a huge relief for your wallet..COMPATIBLE WITH ANY USB PORT: These batteries are chargeable with any USB port. Plug them into your computer, or use your 4Patriots Patriot Power Cell to charge them on the go. And since they recharge over 500 cycles, you'll have long-lasting & durable D power when you need it..SUSTAINABILITY: Your batteries recharge up to 500 cycles. That way, you won't be throwing away buckets of dead batteries. These rechargeable D batteries are climate-friendly & a great source of green energy. That way, you can make a difference with your power consumption.