Replacing UPS Battery After Low Battery Warning

I’ve gotten email notifications from my FreeNAS file server that my APC ES-725 UPS has a “low battery” condition. The 12-volt battery inside the UPS was no longer outputting a constant 12 volts to provide backup power during an outage. When that happened three years ago, I ignored the emails for several months. One day the UPS stopped working and started whistling loudly. I had no choice but to unplug the UPS to stop the whistling. My choices then was the same as now: replace the battery or the entire UPS. Most of the time, it’s cheaper to replace the battery.

I inherited this UPS from my father after he passed away in 2012. His approach to PCs was to buy a $300 USD Dell box. When all the Double-D naughty bits slowed down his computer after two years, he bought another $300 USD Dell box. If it wasn’t for the Double-D naughty bits, he wouldn’t had to replace his PC every two years.

Whenever he bought a new PC, I drove up to Sacramento to transfer the data between the two Dell boxes and bring the old Dell box home to use as a file server. I stopped using Dell boxes for my file server when FreeNAS switched to ZFS for the file system. I built a new system to meet the higher hardware requirements in 2015.

A 725VA UPS was too much backup for the Dell box, monitor, keyboard, mouse and DSL modem that he had. I’m not sure if he wanted more backup power just for the sake of having more power or a salesperson talked him into buying the most expensive UPS at Walmart. A UPS at half the backup power at half the price would have been enough to properly shut down his system during an outage.

The manufacturing date for the UPS was December 14, 2003, making it 16 years old last December. The original APC battery was 13 years old when I replaced it in 2017. A typical UPS battery should last between three to five years, depending on the number of recharging cycles. Frequent recharging cycle reduces the lifespan of the battery. The Universal Power Group UB1270 replacement battery with a two-year warranty that I got from Amazon lasted three years.

My UPS sat in the back corner underneath my desk for the last three years. I shut it down, unplugged everything, and dust off the accumulated dust bunnies with a microfiber cloth. I turned over the UPS to remove the back panel to access the battery compartment. The cables are very short, and, with my fat fingers, I didn’t have much space to unplug from the terminals.

The battery had some corrosion at the terminals, where lead acid leaked out from inside the battery. Avoid touching the corrosion. If you do touch the corrosion, avoid touching your face and wash your hands with soap and water. The corrosion was on the outside of the connectors and I didn’t have to clean the inside of the connectors.

When I tested the battery with a voltage meter, the battery had a 10-volt charge. Under 12 volts and corrosion on the terminals is why it had a “low battery” condition. When disposing of the old battery, make sure to comply with local regulations regarding the disposal of e-waste. Just don’t toss it in the trash.

I re-ordered the Universal Power Group UB1270 UPS battery from Amazon. After removing the battery from the box, I tested it with the voltage meter. The new battery had a 12-volt charge and clean terminals. Just be careful when connecting the cables to the terminals and putting battery back inside the compartment.

Replacing the UPS battery cost me $20 USD. If I replaced the entire UPS, it would have cost $80 USD or more depending on the model. This 16-year-old UPS is still running fine on its third battery.

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