Most Li-ion batteries have a maximum charged voltage of 4.20V/cell, and every reduction in peak charge voltage of 0.10V/cell is said to double the cycle life. For example, a lithium-ion cell charged to 4.20V/cell typically delivers 300–500 cycles. If charged to only 4.10V/cell, the life can be prolonged to 600–1,000 cycles; 4.0V/cell should deliver 1,200–2,000 and 3.90V/cell should provide 2,400–4,000 cycles. A lower peak charge voltage reduces the capacity the battery stores. As a guideline, every 70mV reduction in charge voltage lowers the overall capacity by 10%. For absolute best longevity, the optimal charge voltage is 3.92V/cell (this may vary with chemistry).