FOCUS WINTER PREP
KEEP ON
RUNNING
On 10 August, almost a million people were
a ected by a major power cut across large
areas of England and Wales, a ecting homes
and businesses and stranding thousands of
passengers across the transport networks. The
blackouts were caused by problems with two
power generators, according to National Grid. The
fact that the blackout happened in summer and
not during the darkest days of winter was seen by
many as good fortune.
But you can’t rely on luck. This is why, regardless
of whether you are a small business or giant
corporation, it’s unwise to leave the capabilities
of your generator to chance. Proper maintenance
of generators is essential if you want to ensure the
smooth running of your business throughout the
long winter months. Downtime can be costly, and in
extreme cases, even dangerous.
Dead batteries are a leading cause of generator
service calls, and one which can be largely avoided
with the right preparations in place. Uninterruptible
power supply (UPS) battery management is
essential, with the UPS system being totally
dependent on its battery backup in order to perform
as required.
Batteries are an o en overlooked area, even
though they have a vital role to play – particularly
38 SEPTEMBER 2019
in environments such as the operating theatres of
a hospital or a flight control tower. If the backup
batteries fail following a mains blackout, the UPS
would drop its critical load - with potentially lifethreatening
consequences.
Batteries in UPS systems are at particular risk of
damage in winter, due to freezing and condensation
causing water damage. They also need to be checked
for a clean and tight connection on all terminals,
ensuring that there are no loose, dirty or corroded
terminals that might cause a problem when power
is required.
Battery tests as part of general maintenance are
important, but a good result should not lead to
complacence – particularly during winter. Passing
a battery test doesn’t necessarily guarantee the
batteries will be su iciently resilient for supporting
the UPS at the full load autonomy it was designed for.
This could be for several reasons:
The UPS battery test duration may only be for a few
minutes, when in reality the UPS may need to support
the load for a longer period.
One or more ‘bad’ battery blocks (usually with high
internal impedance) will o en, under su icient load
conditions, drag a whole string of batteries down,
meaning the UPS will not be supported. The UPS may
detect and see the DC circuit from the battery string as
being open circuit.
An increase in the UPS’s output load or changes
in ambient temperature between maintenance visits
could also a ect the performance of the batteries
under a load test. There have been cases where a
failure to an airconditioning unit located with the UPS
battery has gone unnoticed. With no climate control in
place, the room temperature can reach as high as 40
degrees. The heat, even for a short period, can lead to
leakage and swelling.
The maximum lifespan of a UPS VRLA/SLA type
battery will vary, with most manufacturers quoting a
maximum period based on optimum environmental
conditions. The reality is that most installations are far
from perfect when it comes to environments, with the
operating temperature having a significant e ect on
battery life and performance. At low temperatures the
performance of the battery is reduced, while at high
temperatures the battery reaches the end of its life
more quickly.
If the UPS charge float voltage is not configured
correctly or the charger is faulty, this could cause
irreversible internal damage to its batteries.
MAXIMISING BATTERY LIFE
There are many simple measures to ensure the
battery remains reliable throughout the winter
period. By checking and monitoring the impedance
of each battery block, for example, any bad blocks
can be identified and replaced ahead of any failure.
UPS battery installations should ideally be in
designated UPS battery rooms with adequate
ventilation and suitable air conditioning. Daily
checks will eliminate the risk of failing aircon units
going unnoticed. Where the UPS and its batteries
are in the same room, there should be su icient air
flow and climate control; even with aircon units set
to 20 degrees, the ambient temperature around the
batteries can be significantly higher.
It’s preferable to install battery strings on open
racks rather than inside a UPS or battery cabinet.
Batteries on racks are more accessible for servicing
and inspection, while cabinets restrict air flow and
trap heat.
If you are protecting a critical load with a single
UPS, opt for a battery bank comprising multiple
battery strings configured in parallel. It can be costly,
but if one string fails the remaining strings will
provide the necessary backup. Again, if your critical
load is supported by a parallel UPS system, each UPS
module or unit should have its own string of batteries
as opposed to a common, single bank of batteries. If
one UPS module fails, the remaining UPS units will
still provide backup.
Finally, for ageing batteries it’s worth considering
carrying out a battery load bank test. This involves
placing the UPS on external bypass or continuing to
operate the UPS with the load not protected for the
duration of the load bank test.
A UPS system depends on its
battery backup to maintain power
following a blackout – but winter can
be hard on batteries, warns Stephen
Peal, Director of PPSPower