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How Does Design Life of a battery differ from Service Life?
As an industrial battery charger manufacturer for 30+ years, a very common question we always hear from our new customers is that “how come if I buy a battery with 15-year design life, I get only 10 years or less from my battery?” We must discuss service life and understand how it differs from design life.
First, let’s define service life of rechargeable batteries including Lead acid battery, NiCd battery and Lithium Battery. Service Life has been defined as the “period of time during which, with a given load and by following the maintenance instructions, the specified limits of reliability characteristics will be fulfilled for all contemplated units, (e.g. same type of batteries).” If we can paraphrase with a simple English translation, service life is “the actual battery life experienced from a cell or group of cells under actual installed conditions.”
It is important to understand at the outset, there are several things that affect service life:
1. Temperature – probably one of the most important factors
2. Frequency and depth of discharges
3. Maintenance practices – considered by many to be a root cause of many failures
4. Lack of understanding the true load profile and/or the application
5. Type of battery chosen for the given application
6. Undercharging or overcharging the battery due to an incorrect voltage setting of rectifier/charger to the required battery voltage
7. Undercharging or overcharging the battery due to a lack of synchronization between the voltage reading and the actual voltage at the battery terminals.
8. Excessive ripple to the battery
9. Other environmental factors – temperature or voltage gradients within the string, flooding, etc.
10. Quality of Installation
11. Actual manufacturing defects
Each battery manufacturer outlines expected maintenance practices that must be in order to ensure that the battery will perform correctly whether it is AGM Battery, Gel battery, Flooded battery, or Lithium iron phosphate battery. What these operating instructions do not state is what happens if these practices are not , nor do they account for many of the variables listed above that a user experiences in his day to day applications. We do know though that these “stress factors” can shorten battery life.
Let’s look at just a few of these factors and highlight the effect that could impact service life. It is a given that temperature plays a major part in either extending or decreasing service life. However, it is important to note that the temperature effect is not linear. Increased temperatures on a battery cell are more severe in shortening service life than cooler temperatures are in extending it. It is commonly accepted that for every 10°C rise in temperature continually applied to a battery, the result is a reduction in battery life by approximately 50% (See Figure below).
Another “stress factor” that can severely affect service life is undercharging or overcharging the battery. Undercharging the cells will lead to plate sulfation with a resultant buildup in internal resistance within the cell while reducing capacity and eventually shortened battery life. Conversely, overcharging the cells leads to accelerated positive plate corrosion, and eventually shortened battery life as well.
Among all these factors, you can rest assured that you will get the maximum service from a battery if you choose your manufacturer wisely. With a top brand like Greentech, you can ensure the manufacturing excellence and quality of the battery raw materials, and the reliability of your operation.
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