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.
