Temperature significantly affects the performance of UPS systems. Four different UPS systems
were evaluated at sub-zero temperatures and hot temperatures from -25 °C to +72 °C (-13 °F to
+162 °F). At high temperatures, tests were performed to ascertain the run times under normal
signal operation, whether the UPS shutsdown the charging and that there is no gassing of the
batteries. At sub-zero temperatures tests were performed to find the run times under normal,
flashing and a combination of normal and flashing modes of operation. All the UPS systems
showed longer run times as the temperature increased and drastically shorter run times as the
temperature decreased. For normal operation at +72 °C condition, the percentage change in run
time relative to room temperature ranged from +6% to +26%. Relative to room temperature the
percentage change in run time at -25 °C condition ranged from -32% to -80% for normal
operation. At the coldest temperature, the increase in duration of flashing compared to duration
of normal operation ranged from 89% to 158% and the increase in combination of normal and
flashing duration compared to normal operation duration ranged from 35% to 81%. It is
recommended to switch to flashing or a combination of normal and flashing mode of operation in
cold temperatures to increase the run time. It was also found that a UPS with a greater battery
capacity may not yield greater run times under all temperature conditions.The Illinois Department of Transportationpublished or submitted for publicationnot peer reviewe
