UPS Calculations

Hardware
1

I got an Eaton 3S 700 UPS to service my Home Assistant and Router. It’s rated at 700VA or 420W with a ‘standard runtime’ of 15 minutes. I’d measured the power usage of my HA + Router at 42W so I figured the UPS should give me 150 minutes if the power goes off. This is based on 42W being 10% of the 420W for 15 minutes rating. One of the readings that HA gives me is Load and this is always round 10%. so that stacks up - so far so good :slight_smile:
When I come to test the performance I’ve found that the UPS battery drops from 100% to 30% in 30 minutes, so I might get 45 minutes before it goes flat. This is way off the 150 that I was expecting!

Eaton UPS Outage
Eaton UPS Outage2222×1050 151 KB

Am I dumb to believe what the marketing blurb tells me or am I just interpreting their spec wrong (dumb again)?

2

Not dumb. But, understand that marketing is just that.

And, seldom do batteries stack up to any marketing.

3

I got a Cyberpower ST625U for my RV and it stayed on with my HA rPi, Pi-Hole rPi, Netgear cellular hotspot and my Netgear router for at least 6 hours, I know this because I left them running after I unplugged the RV for the next leg and we kept on the RV wifi network, and using the Internet, for the entire leg of that drive.

4

How old is the battery? What is the efficiency curve of the UPS? Lower quality models generally are not efficient at low loads.

5

It’s new. I’ll look into the efficiency curve if I can find such a thing.
Edit: Just came across this graph for my product on the Eaton UPS website. It shows I can expect about 45 minutes at 42W which is what I’m getting.

Eaton UPS Runtime.jpg
Eaton UPS Runtime.jpg1241×1110 67.1 KB

It seems that the 700VA/420W is max output and the Standard Runtime of 15 minutes is unrelated despite being on the same bullet point in the spec on the Amazon website. The fact they can quote a Standard Runtime without saying how it’s derived is disingenuous. I’ll be pointing it out in my review.

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