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Have low-end UPS units gone lithium iron phosphate yet? That's the battery technology of choice now for non-portable applications. Cheaper and longer-lived than lithium-ion, no thermal runaway risk, about the same energy density per cubic meter, but twice the weight.

Such UPSs are available in small rackmount units.[1] The usual serious players, such as Tripp-Lite, have LiFeP04 battery powered units. Searching for consumer-grade LiFePo4 UPSs turns up many articles on how to replace crappy batteries in UPS units with newer battery technology. The batteries themselves are cheap now. APC doesn't seem to have caught up yet.

This looks like an APC corporate problem.

[1] https://www.falconups.com/ups/lifepo4-ups-sl.htm

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> Have low-end UPS units gone lithium iron phosphate yet?

no, and afaik it's a cost thing. the unit you link is "request for quote" and being a rackmount unit it's probably not what consumers would think of as inexpensive.

I have three of the classic fire-hazard cyberpower 1500PFCLCD and each of them has a pair of small sealed lead-acid (SLA) batteries that cost maybe $30-40 each to replace. If you assume that the OEM gets them for $20 apiece, how much LiFePO4 battery does that buy? I know the big industrial cells are cheaper than what you can get as small individual cells, but I'm positive it's still going to be 4-10x more expensive.

now remember that's a unit that retails for $135-150, and there are like 3-4 tiers of units below that... how much LiFePO4 can you buy for $10 to put into that $50 UPS?

(fake edit I looked one of them up from the datasheet and it's $700 for the lowest-tier 1000VA unit lol)

> (fake edit I looked one of them up from the datasheet and it's $700 for the lowest-tier 1000VA unit lol)

That's the bigger issue, that there's nothing medium price.

I can get a LiFePo4 battery that can do well over a kilowatt for an hour for <$150 with free shipping, and I can get an entire UPS for <$100, but the combination costs so much more.

It’s not only a cost thing, they don’t have the power output for the same form factor. You can technically swap in those 12v LiFePo4 “replacements” into a cheap UPS but they don’t put out nearly as many peak amps as good old SLAs. Lithium Ion and Polymer can but they also run the risk of blowing up. I’ve played with basically all these chemistries doing model airplanes and DIY drones.

I thought the bigger concern was that the charge and duty cycle of the different battery chemistries were incompatible so it was not a good idea to swap lithium based batteries into lead acid ups's.

If someone knows different, I'm all ears.

One of those modding articles discusses how to reprogram the UPS's battery manager with numbers suited to LiFePo4. A bit iffy, that; who's validated those values?

Most of the packaged-up drop-in replacement lead acid to LiFePO4 batteries I am seeing aren't just a group of raw cells, but have a battery management system internally. Even the least expensive should be able to protect the cells from overcharging without modification to the UPS.

From what I read, it's not the overcharging or the charging that is the issue, it's the cutoff voltage at which a lifepo might be harmed being a higher threshold than a lead acid battery, so you have to have a BMS for the lifepo which increases the cost and can cause the ups system to miscalculate runtime as it may cut off when it thinks it has 10% remaining.

But if there is a hack to recalibrate them, then great. I'll do some searching for it now as I have two little bms's that need batteries.

Has anyone tried the new anker or ecoflow lithium portable power stations as a UPS?

It's very likely their switching time between wall power and battery isn't quick enough to keep a computer on. With ATX you need to switch power in no longer than 16ms else the computer will shut off.

Ecoflow switching time is listed at “<30ms” and the new Anker power stations are listed at “<20ms” so not the speed you’re looking for. APC’s tend to be listed at less than 12ms.

EcoFlow has non continuous output. Shouldnt be a problem for PC, but some loads ae sensitive to it:

EcoFlow Delta Pro - RTFM Dummy! EEVblog2 https://www.youtube.com/watch?v=5JT8M8v_zNg

Bluetti dos much better:

Bluetti AC500 / B300S Power Bank - Review & Teardown mikeselectricstuff https://www.youtube.com/watch?v=RuEO17uvI8M

> The batteries themselves are cheap now.

> about the same energy density per cubic meter

Energy density isn't the issue. Need to either buy the best cells or oversize the pack to meet normal loads. Both options cost additional money.

Go look at the spec sheets on the cheap ones, they aren't power dense enough to make a small (1000-1500VA) UPS with comparable or even double runtime of the lead acid.

Lithium not common for 120V, but I have several APC CP12142LI units for 12V devices. (No USB monitoring, and they're not terribly price-competitive for the capacity, but they've worked well for me.)

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