Power for home lab/office

Handruin

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I'm sure how to tell if these batteries are past their useful life. I took the pack out and all four batteries were cool to the touch so I don't think my UPS continuously cooks them or runs warm. None of them were bulging or leaking anything and the pack was easy to slide out. I can pull the plug from the wall for a couple minutes and it runs a 600W load.

I measured the voltages on the cells and they read 13.4V on each cell or 26.9V on each pair. Should I still replace them?

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LunarMist

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It's a a question of how old they are. I have a special battery thingamajig, but you can put a constant load on them and test capacity manually. Your UPS is a 1500VA model?
 

Handruin

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Yes it's 1500VA model and the batteries are from January 2017 (6.5 years).
 

LunarMist

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They will die soon enough and you don't want it to happen at a bad time when your NAS and computer experience an uncontrolled shutoff like mine. :(
 

Handruin

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That's fair. I went ahead and ordered the 12v 8AH Duracell you mentioned and got the 18% off.
 

Handruin

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Batteries got swapped and it was was easy enough to replace the 4-pack. I'll let it charge overnight and see how the voltages are.
 

LunarMist

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All the AGM batteries are designed to float around 13.5-13.8V at room temperature. The 6 small UPS I've recently tested are all between 13.52-13.67V per battery. A large one is 27.1V and the other one cycles around 26.9-27.2V. There may be some hysteresis with the panel meter, but a graph shows spikes. I suppose that is normal since it's been that way for many years.
 

LunarMist

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I wonder what JTR thinks about most UPS charging batteries from bulk to float without an absorption stage like a typical charger? How many hours are needed at 13.5-13.6V to reach 100%?
 

Handruin

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I just checked again with my voltage meter and 13.5V (27v for the pair) after charging so it's consistent with what you mentioned. I don't have any insight into the UPS charging mechanism.
 

ddrueding

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I suspect it is due to the expected use cases. Sitting fully charged 99% of the time, with the occasional significant discharge spaced apart by months. It would be better if it wasn't, but likely a cost cutting measure.
 

LunarMist

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It's possible that the float is enough because the battery is always on charge and not set aside. If the last 15-20% takes several hours or one hour may not make a practical difference.
 

LunarMist

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My test results of the two 12V-9Ah FR are not so great. I'm not seeing much more capacity than the 8Ah and not a lot less impedance either. I'll put them in an olden APC 1300VA UPS for an AV center but it's not worth the one-third extra cost over 8Ah IMO. In my 24V 1500VA UPS with six (2 int/4 ext) batteries the FR (high rate) are definitely not needed since the drain on each is 1/3 of the 2-battery types.
Anyways, I am done with batteries for now (about $400 worth in a month or so).
 
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