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Comment by rootusrootus | Hacker News Reader

I'm giving some thought to brewing up my own UPS. Mostly for capacity, which is tough to get in a residential unit at any price, and quickly becomes expensive if you try. Technologically, it is not particularly difficult. You buy a halfway decent inverter/charger from a reputable manufacturer, and however much LiFePO4 capacity you want. I would not choose lithium ion; LFPs are considerably less likely to combust.

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A few years ago ESR started on an open source/hardware UPS project called Upside.[0][1] I can't vouch for the design as I haven't looked at it in a long time.

[0] http://esr.ibiblio.org/?p=7839

[1] https://gitlab.com/esr/upside

How do you achieve the X <= 10 ms switching capacity? You need this if you actually want your equipment to survive the power outage.

Also, I'm extremely sensitive to humm noise output by inverters so I can only tolerate UPSs that have that "Green mode" option which (I guess?) powers directly from AC when under quality power but still provides protection.

Capacitors or using a circuit where the battery is always supplying power (can't remember what it's called).

Could make a post-PSU UPS, then you don't need an inverter at all (also the most efficient design, no conversion losses)

My preferred inverter/charger manufacturer, Victron, has "UPS Mode" for their Multiplus units that will switch in 12ms. That's similar to many UPS's, though some of the higher end ones are sub-10.

Please post a parts list if you do!

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