Lithium-ion batteries control much of our lives today in cell phones, laptops, tablets, fitness bands, bluetooth headsets, lawn mowers, drones, cars and boats. The shorter their life expectancy the harder it is on the environment with more resources taken from the earth. The financial drain on budgets from buying replacements is another incentive to extend their lives. Most consumers are not aware of the proper care which can maintain their capacity and make them last as much as three times longer.
Unfortunately things like cell phones autofill to 100 percent when left on a charger. The number of battery cycles can be doubled by filling the battery to only 86 percent. A cycle is the discharge and charge of a battery’s full capacity one time, not just all at once. Removing the battery from charge at 90 percent full is better than 100 percent; 80 percent is better than 90 percent.
Although many people think this is best, do not keep a battery at full charge. Chemical reactions occur more often when a battery is at 100 percent and are costly to the battery’s life. It is even worse to keep a battery at 100 percent for extended periods of time than to fill it to 100 percent. As a comparison, a battery stored at 100 percent charge for one year at 77°F permanently loses roughly 20 percent of its capacity. Under the same conditions but at 40 percent full it will lose only 4 percent capacity. Studies for the best long-term battery storage have shown that 40 percent is the optimal charge level.
Do not let a battery be used to 0 percent full capacity either. Dropping from 80 percent to 30 percent twice is much better than from full charge to zero percent one time. It is not as harmful as overcharging the battery but it does do damage. And the management protection circuits have no operating power in a discharged battery. The optimum level to make it last is maintaining a middle charge level as much of the time as possible.
Do not leave a cell phone on a car’s hot dashboard. Keep batteries away from heat since harmful chemical reactions occur more often at high temperatures. This is most important when charging or discharging the battery, although storing it at high temperatures is also shortens its life. A battery stored at 40 percent charge for one year at 104°F loses 15 percent of its capacity, where at 77°F it will only lose 4 percent.
Do not let a battery get too cold. Although this is not as harmful as getting too hot, the battery will empty faster. The battery will heat itself up a little while it is charging or discharging, but capacity is lost during cold periods. The ideal room temperature for batteries is the same as for humans, between 70 to 75 degrees.
The type of lithium-ion battery affects the rate at which it can be safely charged or discharged. But a common fact to all is that the faster it is charged or discharged, the shorter the lifespan of the battery will be, with the problem intensified from heat generation if the battery is not actively cooled. The slower the charge and discharge, the longer the battery will last. “Power optimized” batteries are made with a chemistry that better handles high discharge rates. Specific chemistries and nano technology factor in many more details.
It is difficult to control charge levels since most chargers do not stop until the battery is full. This is not the case in electric vehicles like BMW and Tesla Motors where the batteries can be controlled more easily. Read the Battery University website for much more detailed information and to ask questions.