Useful Life - NorthStar NSB12-310 Applications Manual

3.3 Cold Temperature Performance
Colder temperatures can prolong battery life because
corrosion processes within the positive plates of the
battery slow down as the temperature decreases.
Unfortunately, lower temperatures also lower the
capacity of lead-acid batteries. As battery temperature
drops below the recommended operating temperature
of +25° C (+77°F), the battery capacity decreases.
4

Useful Life

4.1 Shelf Life
NSB UPS batteries may be stored for up to 2 years
provided that the OCV is never allowed to fall below 12.1
V. Failure to provide the required maintenance charging
(see Section 3.1) may lead to irreversible capacity loss.
4.2 Design Life vs. Temperature
Lead-acid batteries operating under float conditions
are continually being charged. As a result, the lead
grids within the positive plates undergo slow corrosion,
which is a normal aging mechanism under float duty.
Typical UPS applications require short duration high
discharge current (5 to 15 minute rates) to support
the load. It should be noted that the presence of grid
corrosion increases internal resistance which, in turn,
decreases the available power. This behaviour is more
obvious for higher-rate UPS duty, than during the lower-
rate telecom applications.
The rate of grid corrosion increases with increasing
temperature and, as a result, the temperature of batteries
has a large affect on their float life. For each increase of
10°C, float life will decrease by a half. For example, if the
temperature rises from the recommended operating
temperature of +25°C, to +45°C, the expected life of the
UPS battery will decrease from 15 years to less than 2
years (see chart below).
Form: SES-541-01711
As seen in the above graph, the batteries design life will
vary significantly due to differences in discharge rates
and environmental temperatures.
Under float duty, a battery is considered to have reached
its end of life (EOL) when it can no longer deliver 80%
of its original rated capacity. For example, a 100 Ah
battery has reached EOL when its discharge capacity
has dropped below 80 Ah. The relationship between
capacity loss during float duty and battery temperature
is shown in the following chart:
5 Technical Specifications
For detailed technical specifications, please refer to the
product data sheets provided at www.northstarbattery.com
Issued: 12-08-16 ECO-101191