What are the factors that affect Battery Rated Service Life?

Issue:
What are the factors that affect Battery Rated Service Life?
On paper, batteries are given a design life of 5 years, 8 years, 10 years, etc.  They get weak, or fail sooner than there rated lifespan.  That is their Service Life

Product line:
Symmetra, Galaxy, EPS, Smart UPS, Battery

Environment:
All models, all serial numbers

Cause:
The design life is the life expectancy the manufacturer says the battery is capable of, provided that all of the specification parameters are maintained.

The main things that affect battery service life.
1)Design Life -
• Float voltage accuracy
• Frequency of discharges
• Number of discharges
• Maximum discharge rate
• Depth of discharges
• End voltage limit
• Operating temperature
• The amount of ripple current and voltage allowed, during charging as well as discharging. This is a very strict regimen that has to be followed very accurately in order to achieve the Design Life. Not many installations can maintain that level of control.

2)Temperature – The standard is 25 C (77 F).
•  This specification is for the internal temperature of the battery, and not for the ambient room temperature.
• Keep in mind if batteries are installed inside a cabinet, the internal temperature of the battery is usually 2 deg warmer than ambient air, and temperature at the top of the cabinet can be 10 F warmer, than at the bottom.
• CAUTION: Battery life is halved for every 10°C above 25°C.

3)Duty Cycle – This is how often the battery charges and discharges.

4)Environment -   The VRLA battery is specifically designed to be installed
in occupied spaces, meaning the places where people normally work.
• Corrosive environments are not places where people normally work.  Care must be taken to ensure that the environment is not corrosive.
• Charge / Float Voltage
• Charge Maximum Current
• AC Ripple
• Maintenance of fluid levels, terminal torques.

Resolution:
If one looks at these terms, and considers them with the simplest explanation, it is easy to see that Design Life is the life expectancy the manufacturer says the battery is capable of, provided that all of the specification parameters are maintained. It is also relatively easy to see that, because of the real-world physical and electrical environmental variables, it is highly unlikely that the Service Life will be anywhere near the Design Life.

Reference:
Sample Battery Spec Sheet: CSB-HRL-1234W-F2FR.  Page two has various charts to estimate the effects of duty cycle, battery storage, and temperature on service life.  These types of spec sheets can be obtained from the battery manufacturer.

APC_WHITE_PAPER 230: Lead Acid Battery Lifecycle

Publié pour:Schneider Electric Belgium