Is it true that we should not leave cell phones and rechargeable batteries beyond the normal time, indicated for full charge by manufacturers?
For low-cost chargers without intelligent charge control, this is true as they continue to circulate a strong current through the batteries even after they are fully charged. This current keeps the battery warm, which means a wear and tear, with the reduction of its useful life. However, the more elaborate (more modern and more expensive) chargers are smart, cutting off the current in the cell or battery when it is charged. So be aware: in a simple, low-cost charger, you control the charging time. In the intelligent charger, there is nothing to worry about as it shuts off when the charge is complete.