UPS's come in threes
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A few weeks ago, I was writing up a report for my university course, on some testing that I was doing surrounding efficiency of computer systems. It was focused on what varying the cores enabled and hyperthreading did to the efficiency of the system, using an Intel® E3-1270v3 CPU for the tests. I was looking into efficiency, therefore I wanted to measure wattage against the relative performance
When designing my testing, I looked into a way to both control and measure mains power. This was needed, as Wattage (W) = Voltage (V) x Amperage (A), so a variance within the voltage provided had the potential to cause a large error in my findings, as the systems PSU efficiency would be changed. During my research, I found the most common way of trying to minimise fluctuation was to either use a UPS, or to measure the voltage, and use that to ensure tests were consistent.
When it came round to time to purchase the needed equipment, I quickly saw the high prices of a Line Interactive, Pure Sine wave UPS, and decided to go down the measurement route. To measure the power draw I acquired an inline power meter (available from amzn.to/2R6Ra6X). This tool allowed me to get a measure of the mains voltage running through it, alongside wattage (and the min and max).
In the UK, mains power is supposed to be around 230V (+10%/−6%), which, should result in a minimum of 216.2V, and a maximum of 253V during my tests. I used this to measure the voltage every 30 seconds, then discarded any runs where the mains power had any bursts higher than ±15%, as well as runs that averaged more than ±6% of 230V. This resulted in 3 of my 70 tests having to be redone, which was a lower than expected outcome. I imagine that my flats building's relatively new wiring played a factor in providing such stable mains power.
Having completed my report, and submitted it, I returned home from university and went back to work on Monday, wherein the storage and scraps room there had appeared a new pile of old APC branded kit since I had last been back, looking dusty and dejected. I asked my boss about them and was granted an indefinite loan on them for my lab, with the warning that they were most likely completely dead and non-functional.
I, being a sucker for a challenge, said that I'd take them anyway.
Above : The UPS’s offered, with the batterys stowed away inside them.
That evening after work, the UPS's were loaded up into the boot and took a trip to their new home. I had a look at the pile once it was in from the cold that is a British winter, and found I'd scored a pair of battery-less "Smart-UPS 1000xl" units, an expansion unit for said UPS's, alongside a smaller "Surge Protector + Battery backup 325 VA". Next to the UPS's themselves were a pile of cells and cables which I took at the same time, and to my luck turned up, with the right size cells for the 1000xl units, and the expansion unit.
Above : A rear veiw of the UPS’s, showing the power in and out, as well as the expansion box and its leads to connect. A pont to note is that up to ten expansion boxes can be daisy chained, by removing the black plate on the expansion box to allow the next expansion to be mated on.
The cells needed for this type of UPS are APC RBC7 (Available at amzn.to/2SvpaXt), which ends up fairly pricey when you consider that the UPS itself needs one, and the expansion unit two of the same, near enough £700 to fill one UPS + Expansion with new cells from APC. If I end up needing all new cells, it looks like a trip to eBay will be needed, or to use the same funds to get a new, better box.
Above: The front of the UPS battery box when you remove the front cover. There are two screw in each top corner, which when removed, allows the front to hinge down and provide access to the cells.
I then opened up both the UPS’s, and the expansion boxes. There was minimal visible wear and tear within the two Smart-UPS 1000xl units, with the only box with any visible wear being a small amount of battery corrosion allong the base of the expansion unit.
Above: Corrosion on the base of the UPS
While I had the unit open I had a look at how the cells connect in, which is done via two plugs on the roof of the UPS, utilizing the same plugs as on the rear of the unit.
Above: There are two sockets within the expansion box for extra APC RBC7 Cells to be added.
One thing to be mindful of within the expansion units is the cooling of the cells (especially under charge and discharge) as there is only a small amount of perforation towards the rear, and no fans present to assist in cooling. This is likely negated if the air surrounding the box is moving and cool.
Next up is to measure and test the cells, and the UPS's themselves.
Resources and references:
en.wikipedia.org/wiki/Mains_electricity - A good opening read for learning more about mains power all over the world. It’s wikipedia, so be cynical and check the references.
esfstream.com/watts-volts-and-amps/ - Shows a clear diagram for the relationship between Watts, Volts and Amps. A familiar sight to those who have studied physics or electronics, I’m sure.
www.apc.com/shop/uk/en/products/APC-Smart-UPS-1000XL-230V/P-SU1000XLI - The manufacturers webpage for the larger Smart-UPS 1000xl units. The manual for the UPS is also available here.
www.apc.com/shop/uk/en/products/APC-Back-UPS-325-230V-BS1363/P-BE325-UK - The manufacturers webpage for the Battery Backup and Surge Protector 325va unit. The UPS manual is also available here.