Long Cycle Life

Valence’s Lithium Iron Phosphate Battery has a long cycle life

Traditionally, the cycle life of a battery is the number of cycles of charge and discharge a battery can undergo while still retaining 80 percent of its initial capacity. The 80% limit is a legacy value left over from lead acid battery testing because once a lead acid battery has reached 80% of original capacity, it may exhibit sudden death as the capacity can decrease rapidly thereafter.

As a result of our stable, high-quality chemistry, the Valence product line has superior cycle life compared to lead acid and lithium mixed oxide batteries. Valence batteries have a slow predictable fade with no sudden drop in capacity.  In fact, one can now use the battery until the energy drops below that needed in an application rather than arbitrarily stop at 80%. Valence lithium ion batteries can keep supplying energy down to 70%, 60% or even 50% of original capacity. And even then, they could be transitioned to another application where the rest of the capacity could still be useful. This benefit is just not offered with lead acid.

As a result of our stable, high-quality chemistry, the Valence product line has superior cycle life compared to both lead acid and lithium mixed oxide batteries as illustrated in the graphic below:

Comparison Cycle Life
100% Depth of Discharge at C/2

The lithium-ion battery works on ion movement between the positive and negative electrodes. In theory such a mechanism should work forever, but cycling, elevated temperature and aging decrease capacity over time. Manufacturers take a conservative approach and specify the life of Li-ion in most consumer products as being between 300 and 500 discharge/charge cycles. A battery may fail before that time due to heavy use or unfavorable temperature conditions. Valence’s lithium iron magnesium phosphate battery lasts thousands of cycles. This is why it’s an ideal solution for industrial deep-cycle batteries.

Valence Lithium Iron Magnesium Phosphate Battery and Depth of Discharge

Very few applications discharge the battery down to 100% Depth of discharge (DoD). If they do, they severely hurt cycle life of lead acid or LCO batteries. Valence batteries can be discharged to any DoD without any harm. Since applications can vary their DoD, cycle life varies as well. Notice that changing from 100% to 80% DoD doubles the cycle life. And one can double it again from 80% to 50% DoD. Energy throughput is still exceptional no matter what DoD the battery experiences. Partial discharge on Valences’ lithium iron magnesium phosphate battery is fine. There is no memory and the battery does not need periodic full discharge cycles to prolong life.

The below graphic highlights our cycle life based upon Depth of Discharge usage: