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[Request for Recommendations] 1U-4U Uninterruptible Power Supplies (lemmy.inbutts.lol)

submitted 11 months ago by [email protected] to c/[email protected]

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I recently stated out loud that my homelab was stable, and now my UPS is posting less than 30 minutes of estimated normal load. What's everyone using as a UPS?

I've been rocking the aptly-named CyberPower OR1500LCDRT2U for the past few years. Should I just replace the cells or upgrade the whole unit?

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[–] [email protected] 4 points 11 months ago (3 children)

Probably just a case of replacing the batteries, but if you want to think out of the box: there are some hybrid inverters for solar systems that offer a UPS mode. So you could combine a home solar system with modern lithium batteries with your homelab needs for a better UPS.

[–] [email protected] 9 points 11 months ago

This is the $10k solution to the $100 problem I was looking for, thank you for the idea.

"My dear significant other, the server's battery backup is dying -- I'll be on the roof."

[–] [email protected] 2 points 11 months ago (1 children)

The primary concern is switchover time. A purpose-built UPS can switch in about 10 microseconds. Those large "solar generator" battery packs switch in about 30 microseconds. That might be fast enough, but it's not guaranteed to be fast enough like a UPS is.

[–] [email protected] 3 points 11 months ago* (last edited 11 months ago) (1 children)

Well, if that is really a concern, you can keep the old UPS with not so good batteries still connected to cover that 20 microseconds difference.

But it is unlikely to matter in a homelab.

[–] litchralee 3 points 11 months ago* (last edited 11 months ago)

Did y'all mean to say milliseconds, and not microseconds? Sub-millisecond power loss would be less time than one AC cycle, whether 50 or 60 Hz.

Anyway, I do recall seeing some enterprise gear specifying operation through a drop in AC power lasting two cycles, precisely to cover the switch to UPS power, at least for 60 Hz power. So up to 33 milliseconds. A cursory search for hybrid inverters online shows a GroWatt with "<20ms" switchover, so this may be fine for servers and switches, when the inverter is operated without any solar panels.

For consumer grade equipment, all bets are off; some cheaper switch-mode power supplies do very weird things under transient conditions.

[–] litchralee 2 points 11 months ago* (last edited 11 months ago)

I second this idea, if it's feasible. As noted elsewhere in this thread, the lead-acid batteries in UPS units have a limited lifespan, even if not regularly drained. Solar and off-grid enthusiasts have determined that parity between overall lifetime cost of lead-acid versus lithium batteries was reached years ago, and now it's firmly in lithium's favor, mostly due to the greater number of recharge cycles.

Contraindications for lithium batteries would include:

high local costs for lithium battery packs
lack of space for the hybrid inverter, as they're usually not rack-mountable
the homelab drops below 0 C (32 F), in the specific case of LiFePO4 cells

That said, breathing life into old equipment is usually more environmentally friendly than acquiring new equipment.