Problem description:
My UPS requires new batteries every ~3 months; in this time frame, an average of about 5 to 10 power flickers or short power interruptions (< 2 minutes) occur. After an average of 3 months, a new pair of batteries begins to fail to keep the UPS up during any flicker or power interruption. The load it powers is a single computer/workstation running 24/7 with a continuous consumption between 200W to 300W.
UPS model:
The Atlantis 1001 is a non-inexpensive (~120€ back then) home/office offline UPS, rated 1000VA, 600W, designed for two 7Ah 12V SLA batteries in series, as per its user's manual. The UPS doesn't run periodic battery tests, and just keeps a float charge while on standby.
Troubleshooting:
I opened the UPS while plugged to the mains, powered on, and powering the computer. The float voltage is 26.99V across both batteries, partitioned in 12.85V on the left battery (2.14V per cell), and 14.14V on the right battery (2.35 per cell, see picture). While I took the measures the UPS was not recharging the batteries, these are the float voltages.
The left battery has a corroded negative terminal.
The temperature inside the UPS case feels about 30°C (86°F), approximately. The case has a fan, but it is normally off and spins only while on battery power, so the inside remains always warm.
Interpretations:
The UPS is designed for 600W, or 600W / 24V = 25A on the batteries (~3.5C). Even with half the load (300W, 12A, ~1.7C) the current on the batteries is quite high. I always bought cheap batteries from eBay, so I imagine this is an overload regime. However, very few power losses occur during the 3 months that a new pair of batteries endures, so I imagine this doesn't justify the short lifespan.
AFAIK, the float voltage of 26.99V across both batteries is a good value per se, but badly partitioned across the batteries, so that 12.85V causes sulfation on one battery, and 14.14V causes electrolysis on the other.
The warm temperature also doesn't justify the extremely short lifespan of the batteries.
My UPS requires new batteries every ~3 months; in this time frame, an average of about 5 to 10 power flickers or short power interruptions (< 2 minutes) occur. After an average of 3 months, a new pair of batteries begins to fail to keep the UPS up during any flicker or power interruption. The load it powers is a single computer/workstation running 24/7 with a continuous consumption between 200W to 300W.
UPS model:
The Atlantis 1001 is a non-inexpensive (~120€ back then) home/office offline UPS, rated 1000VA, 600W, designed for two 7Ah 12V SLA batteries in series, as per its user's manual. The UPS doesn't run periodic battery tests, and just keeps a float charge while on standby.
Troubleshooting:
I opened the UPS while plugged to the mains, powered on, and powering the computer. The float voltage is 26.99V across both batteries, partitioned in 12.85V on the left battery (2.14V per cell), and 14.14V on the right battery (2.35 per cell, see picture). While I took the measures the UPS was not recharging the batteries, these are the float voltages.
The left battery has a corroded negative terminal.
The temperature inside the UPS case feels about 30°C (86°F), approximately. The case has a fan, but it is normally off and spins only while on battery power, so the inside remains always warm.
Interpretations:
The UPS is designed for 600W, or 600W / 24V = 25A on the batteries (~3.5C). Even with half the load (300W, 12A, ~1.7C) the current on the batteries is quite high. I always bought cheap batteries from eBay, so I imagine this is an overload regime. However, very few power losses occur during the 3 months that a new pair of batteries endures, so I imagine this doesn't justify the short lifespan.
AFAIK, the float voltage of 26.99V across both batteries is a good value per se, but badly partitioned across the batteries, so that 12.85V causes sulfation on one battery, and 14.14V causes electrolysis on the other.
The warm temperature also doesn't justify the extremely short lifespan of the batteries.
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