Battery design life and the warranty period assigned by manufactures often create a bit of confusion. When batteries are said to have 10 or 5 years “design life” for example the fiamm 12flb350 there can be issues raised related to situations where they malfunction at a particular time within their life period and need early replacement. Also, it is crucial to separate the two, warranty and design life are different terms.
All batteries have a set design life that is arrived at based on the specifications that are required to fulfill the Eurobat Classification. This implies that under normal conditions and functionality, the battery should at least last for the period it was designed for. Service life highly depends on the working settings of the battery, but, in reality, normal functioning conditions are hard to achieve consistently.
These are some of the major factors that affect the service life of a battery:
Temperature, is the main environmental factor that determines the service life of VRLA batteries. Field and laboratory research outlines the standard rule for determining the effect of heat. Typically, with every 10C increase in the mean operating temperature, life is reduced by half. For example, if a battery’s life is 10 years at 20C its life will drop to just 5 years when continuously operated at 30C. If temperature levels swing between these two points the life is determined by a time-weighted average of the temperature oscillations. Normally, this is the major reason for faults in VRLA batteries which prevents them from achieving the established design life from the manufacturer.
Float Charge Ripple:
Immense ripple on the D.C charge throughout a battery diminishes performance and life. It is therefore advised, that voltage control within the system and even the load, but with the battery disconnected, under normal stable conditions, be greater than +/- 1% to 5% to 100% load. Transient, as well as disparate types of ripple excursions, are allowed as long as, when the battery is detached but the load is plugged-in, the system peak to peak voltage, providing for control limitations, stays within +/- 2.5% of the advised battery float voltage. The current flow across the battery when it is working in float conditions should never change to discharge function.
Float Stabilisation Ripple:
This ripple form comes about when the load requirements are out of phase with the rectifier’s capabilities, and the battery is utilized to steady the system. Several static UPS systems act in this way, and the circumstance is almost akin to shallow cycling. Under such conditions, normal battery features cease to apply, and the provider should give the ideal operating conditions.
It is advised that as the user sees it fit, low voltage disconnect capabilities need to be employed in connected systems. However, it is understood that there may be conditions, specifically for system safety factors, under which demands for optimum performance would make it impractical to utilize a low voltage disconnect. When such a scenario arises it might be important to change the battery after a similar discharge.
Failure to replace a faulty battery in a system when it is noted is likely to burden the other set of batteries, implying that the string of batteries could be getting an undercharge or overcharge from the UPS. Over the long term, it will negatively affect the batteries and reduce their service life.
In conclusion, with varied environmental conditions and factors, which extend beyond the scope of the manufacturer and the users’ control, causing the pace of a battery’s degradation, the design life only acts as an indicator or guide on the time a battery may last. Though it is logical to predict a 10-year design life battery to exceed the life of a 5-year design life battery, the reality is that the fluctuating conditions under which the battery functions make it improbable that the design life of the battery and its actual service life will be the same.