Aluminum Encased Batteries Have TWICE the Life of Plastic Encased Batteries
Measuring the life expectancy of a lithium battery is difficult to pinpoint. So we thought that we would like to expound on the subject to help an anticipated lithium user understand the issue and conclude how to get the maximum life from their battery pack.
Understanding Charge Cycle Life – Lithium vs. Lead Acid
Typically the life of any battery is measured in the number of charges the battery has before it deteriorates to a point where it can only hold 80% of its capacity when it was new. This number is called the batteries ‘Charge Cycle Life’.
As a comparison I would like to start with a lead acid battery. Lead acid batteries have a charge cycle life of between 350 charges all the way up past 600 charges. With the lower charge cycle life usually found in car starter batteries and the higher charge cycle life found in laboratory or solar storage applications. But here is where things can become a little misleading. The honest way of measuring a battery’s life can be manipulated. Because of the Peukert effect which exists on all lead acid batteries you cannot discharge more than about 55% of the batteries new 20 hour capacity rating. A 100 Amp Hour ‘Ah lead acid battery will only yield about 55 Ah before it is considered fully discharged.
Lithium batteries are not affected by Peukert’s Law to the extent that lead acid batteries are so you can discharge a lithium battery down to 20% of its full State of Charge ‘SOC’ before the battery is considered discharged. With many lithium batteries if the discharge is more that 80% DOD it will not hurt the batteries life but is generally accepted that the lithium battery is fully discharged at 80% DOD. To run honest tests to determine the exact life of a lithium battery the battery must be fully charged and then fully discharged to 80% DOD.Charging and discharging thousands of times takes a lot of time therefore most companies will do it for a number of complete cycles and then extrapolate the remaining life expectancy based upon some typical known curves for the chemistry of the battery.