
That UPS you bought for your home server may not be as useful as you think - LinuxBender
https://fitzcarraldoblog.wordpress.com/2020/08/09/that-ups-you-bought-for-your-home-server-may-not-be-as-useful-as-you-think/
======
mprovost
This reminded me of James Hamilton's (the AWS datacentre guru) writeup of the
power outage at the 2013 SuperBowl. Specifically how the default configuration
of backup generators is often to protect themselves, even if that means
shutting down the things they are meant to keep running. In my own experience
running a reasonably sized datacentre I was often surprised at how UPSs and
generators reacted to adverse conditions. One thing with power that you don't
want is to be surprised. But it's difficult to test this equipment so it's
mostly a learn as you go experience.

[https://perspectives.mvdirona.com/2013/02/the-power-
failure-...](https://perspectives.mvdirona.com/2013/02/the-power-failure-seen-
around-the-world/)

~~~
cactus2093
> it's difficult to test this equipment

Can't you just flip the circuit breaker or just pull the plug out? Or does a
real power outage usually look different to that in some way, like a surge
followed by a shutoff?

~~~
avh02
Iirc (top of my head), some datacenters go off the grid regularly at peak
(provider) load times and get more favorable rates for doing it. I guess it
ensures your fuel doesn't go stale and all your transfer systems work.

~~~
bluGill
Good point. Many power companies will give you a nice discount year round if
you will disconnect from mains on demand. If you are on the fence about a good
backup generator this will more than make up the difference.

------
iagovar
If you want a poors man home server just repurpose old laptops. I do with a
bunch of them and it's fine. I know laptops are not for that, but they
wouldn't have any other use anyway, and it's like a server with an UPS built
in.

Most tasks are running scrapers or data wrangling so I don't have to keep my
desktop running.

I've been doing this for maybe close to two years, and for now it works. I
wouldn't recommend for VMs though.

Also, your router needs an UPS too but it will be fine with a cheap one.

~~~
drcongo
I've been running a 2008 MacBook Pro as a server for 10 years. I've replaced
the battery once, about 2 years ago, and one of the fans about six months ago.
Other than that, it's been on the whole time.

~~~
dividedbyzero
What OS do/did you run on it? Thinking about repurposing an old 2011 Mac Mini
as a server, it should still be more than capable, but since it stopped
getting newer macOS versions a few years back it wouldn't get security
updates, that kinda worries me.

~~~
drcongo
Just checked, it's actually a mid-2009 MBP and its running 10.11.6 - it's not
had a security update since 2018, which yeah, that is a little worrying. Might
wipe it and install Ubuntu if there's such a thing as Firewire800 drivers for
it.

------
yardie
For those unaware of what the different lines do:

Here is how I differentiate the APC brand:

* Back-UPS: inverter offline, expect a 15-20ms power transfer

* Smart-UPS: interactive, inverter is always online 2-5ms trasnfter

* Symmetra and above: inverter online, voltage conditioned, 0ms transfer

Most desktops will work just fine with the Back-UPS line. The processor is
practically sleeping. Workstations should be on a Smart-UPS because the PSU
capacitor won't have the capacity for a brownout with a Xeon-class CPU and
multiple GPUs.

~~~
borner791
It's more complicated than that. There are Smart-UPS online. Thats double
conversion also 0ms transfer

Some of the "newer" online models will have a green mode, which although
double conversion green mode introduces a transfer time (~2ms, basically relay
lift time).

Backups are also square wave, or stepped sine Smart are Sinewave output.

This is specifically APC.

Also remember there are tare losses (copper / magnetizing and conversions), so
a UPS just sitting there can use up to 30W.

~~~
quesera
Corroborated!

Back-UPS stepped sine wave has about 3 square steps above or below zero, so
it's a very rough approximation of a sine wave. Adequate for many kinds of
equipment, but ugly on a scope.

There is, or used to be, a pin on the Smart-UPS line that you could tie high
(or low?), to tell the device to operate in "Online" mode (inverter always
active, line power continuously tending the battery). APC also sold it
preconfigured that way as a separate, more expensive, product. :)

There's also a trick to jump-starting an unplugged-but-charged Smart-UPS. I've
used this for several hours of remote power in inconvenient locations.

Quality devices, but test them regularly. The switch from idle to high-draw
can be violent, and it takes out weak components. Similar to tungsten
lightbulb filaments.

------
reaperducer
_I live in a place where blackouts are very infrequent (perhaps a couple per
year)_

Ouch. Does anyone know where the author lives that a couple of times a year is
considered "infrequent?"

Decades ago I lived in a rural area of America where we'd have power outages
two or three times a year because of storms. But I've lived in more than a
dozen cities since then, and the power has only gone out twice. Once about a
decade ago during a tornado, and then again last year when the power company
replaced a transformer across the street.

I ask because it's my impression that electric service has gotten much more
reliable over the years. There are still access issues where I live now
(believe it or not, thousands of Americans don't have access to the electric
grid at home), but reliability seems improved. Am I living in a bubble when it
comes to electricity?

~~~
croutonwagon
I live in florida. And in an area where most power is overhead.

Storms during the rainy season usually means i experience cuts. Usually 1-2
times a month for 3-8 hours ea from May-Nov

Hurricanes are usually expected to be 3+ days at minimum of outage. Most
recent ones were closer to 14 days.

I have a couple gennys, and interlock kits with 30a hookups on my house during
these times. I can run 1 genny on the whole house, or even 2 since i have a
sub-panel with another interlock kit.

The only thing i CANT run is my AC. But we have 2-3 window units/portables to
get by.

FWIW running generators for days at a time is NOT cheap. on my setup its about
20-30 bucks a day in fuel alone.

~~~
lostmsu
Why not just go solar? Florida seems like a perfect place for that.

~~~
croutonwagon
Cost. Not worth it.

Even with my roof (which is east/west facing) the cost to just install panels
would be 20-30k. And my city has a 1:1 buy back...And even assuming i sell
them back power it would take a decade to recoup the costs...and by then the
panels would be less efficient. And this is with buying 95% panels.

but then during an outage....

So you need something to store it... Short of rednecking a series of deep
cycle batteries the Tesla Powerwalls are really the only big option.

And those arent cheap either. To run my house for 2-3 days would be in another
10-30k

I can do all of that with 2x7kw gennys and some ancillaries. With a 14-17kw i
could probably run my AC (which have hard start caps on them) Even at 30 bucks
a day in gas im still well south of even 10k.

Next step up would probably be a active standby generator with transfer switch
and giant Propane tank to fuel it. That would be about 10-15k once permitting
and all is done. And that adds complexity and cost. But it would mean i dont
have to manually flip breakers and cutover. (as it is, my computers are just
set to talk to a NUT server, and shutdown in the event i dont cutover within
10 minutes.)

And during storms supply chains are strained. Its hard to source diesel and LP
and sometimes even petrol (in fact i warned a previous company of this, and we
almost had to shutdown due to fuel levels). And you have to maintain a
contract with LP providers and usually rent a tank from them.

With petrol and my little standby units i can source it myself (3-4 am is the
best time during runs on gas), even siphon from one of our cars.

I may spring for a full kit standby one day. But for me, it costs about 2k in
generators. Another 1k to have an electrician install the interlock kits. And
i can service/manage the gennys myself. swap them out while i do maintenance
during extended runs etc.

~~~
24gttghh
What is a 95% panel? Solar cell efficiency is generally in the 20-30% range.

[https://en.wikipedia.org/wiki/Solar_cell_efficiency#/media/F...](https://en.wikipedia.org/wiki/Solar_cell_efficiency#/media/File:CellPVeff\(rev200708\).png)

~~~
Tostino
I believe GP was talking about "95% offset" rather than 95% efficiency.

So he sized the number of panels to offset 95% of his usage is my guess.

------
bob1029
Over the years I have lost a lot of confidence in UPS units which do not use
double conversion topology.

I have a fairly expensive line-interactive unit that can be tricked into doing
bad things just by power cycling my laser printer which is plugged into the
same circuit (but not the actual UPS). One day this caused me more trouble
than it was worth WRT lost work. I would have been better off plugged directly
into the grid and just taking the 100 millisecond voltage dip at the PC's
power supply. This is one area where buying high quality PSU can go a long
way. High wattage Seasonic units can ride through some pretty nasty conditions
before needing any outside help.

I also have a cheaper passive-standby modified-sinewave unit which has never
misbehaved in terms of trigger conditions, but it is hot, noisy and otherwise
does not inspire any confidence when it's running on its inverter. I would
also never dream of plugging anything into this unit that uses a non-switching
power supply.

Again, I am faced with the reality that you get precisely what you pay for. I
always assumed double conversion was expensive paranoia never for home use,
but over time this has proven out just like everything else when looking at
the value equation of technology.

~~~
PaulHoule
My own UPS system is focused around keeping the telephone system and one DSL
modem up and running through 2 days without power. That way if there is a bad
thunderstorm there is no panic about working at home, I can use a laptop and
tablets and communicate as much as I need.

I have a PC tower server and realized off the bat that it would not be
feasible to supply it with backup power for any worthwhile period of time. If
the power goes out it will crash, but it runs on ext4 and ZFS and odds are
very good it will come back when the power does and put itself back together.

~~~
ComputerGuru
I’m with you on zfs (although it is a pain to restore overwritten metadata,
that’s not a typical symptom of power/controller failure) but please change
ext4 to jfs or xfs. Xfs has a bad rep from the early naughts in terms of fs
corruption but actually addressed the underlying issues and today both those
options are equally great.

I’ve tested all three extensively with unreliable media (raspberry pi kernel
dev testing on an sd card) and ext4 was the absolute worst.

~~~
pdimitar
Can you elaborate for which storage mediums ext4 was the worst? The microSD
cards? Or even normal SSDs?

~~~
ComputerGuru
All. Even in the tests where the SD cards never physically failed, their
different write patterns and flushing guarantees exposed underlying issues in
the file system. You just don’t encounter them as often when working on
systems that typically align with the assumptions the fs developers
incorrectly made.

~~~
pdimitar
Quite interesting.

What is the best FS for microSD cards in your experience?

~~~
ComputerGuru
NILFS2 or F2FS, the latter is much more heavily tested as it is now the
default on a number of extremely popular Android phones.

SD cards don’t perform wear leveling so you really need a file system that
minimizes/distributes block rewrites, and a log-structured filesystem will do
that by never rewriting old data (until there is no space left).

------
kcb
The cheap UPSs aren't very good and don't work well or at all with modern PCs.
I've had several of these from Cyberpower that haven't let me down. Far more
reasonably priced than APCs equivalents.

[https://www.cyberpowersystems.com/products/ups/pfc-
sinewave/](https://www.cyberpowersystems.com/products/ups/pfc-sinewave/)

~~~
greenshackle2
Same here, I've had no issues with the 1500VA version. It's line interactive
so _should_ still work if the battery dies, but I can't say that I've tested
it.

~~~
csnover
I don’t know if their newer revisions are any better, but I bought a
CP1500PFCLCD in 2011. When the battery died from old age, it cut power to all
of the battery backed receptacles until I power cycled the UPS. When the
charger failed a few years after that, it did the exact same thing.

------
rcarmo
My APC 950VA also died on me unexpectedly, although I suspect a power surge:
[https://taoofmac.com/space/blog/2020/08/02/1800](https://taoofmac.com/space/blog/2020/08/02/1800)

But the main point in the article is worthy: UPS manufacturers have been
skimping somewhat on functionality, features and quality over the past few
years...

~~~
AdrianB1
No, the article is wrong: the low end UPS devices are bad on quality and
functionality and lead-acid batteries in UPS devices is a lot shorter than
some people would expect.

I still have a few APC Smart UPS's bought in 1999-2000 running in my house; at
the same time I had a few cheapies that broke after a few years, sometimes in
spectacular ways (electronic exploded melting part of the battery case); I
will not name brands, it is not worth.

Since 2000 I changed cases full of batteries, usually every 2-3 years. The
good thing with the APC Smart series is that it works even if it gives an
alert that the battery is bad, but you will get a few minutes of power instead
of 30-60 minutes (my server & NAS is very low power, 5% of the UPS capacity).
I also set the server to shutdown when the battery is reaching 50%, so I never
deplete the batteries. At the same time, the UPS on the water pump is usually
running on batteries as much as it can, so I need to change these batteries
after 2 years. I have both the server and the water pump in the basement, the
temperature is around 16-20 degrees Celsius (winter-summer), when I was
keeping the server and the UPS in the house the battery life was at half (~18
months). The heat and the deep discharge cycles are effectively killing
batteries.

I had the same type of battery on my motorcycles, one lived about 8 years and
a second one 6 years, but in very different conditions: it was warmer, but
almost no discharges.

~~~
zzz61831
Deep discharge is a factor, but not a big one, heat has very little effect, it
only affects voltages at which battery will be considered overcharged or
deeply discharged as specs are usually all for room temperature.

I've used UPSes that discharge batteries no lower than 10.5 (no deep
discharge) and only once in a couple of years and that charge them to and keep
them at 13.6 volts under stable room temperature all year. All batteries lost
most of the capacity after 3 years, two almost all of it, one had like 40%
left. In five years only that one was still surviving short minutes outages,
while initially was able to do a few hours. For comparison, I had one battery
just laying around for 6 years in the same room without touching it and it
lost only like 30%.

~~~
Decade
It turns out that APC intentionally overcharges the batteries to maximize
runtime during the 2-year target battery lifetime, at the cost of killing the
batteries relatively young. And the overcharged voltage drifts upwards over
time.

I found this forum posting while searching for how to maximize the runtime on
my APC UPS: [https://forums.overclockers.com.au/threads/hacking-the-
newer...](https://forums.overclockers.com.au/threads/hacking-the-newer-apc-
upss-mini-worklog-howto.1205748/)

------
ozim
I have a horror story with 700VA APC ES-B700G, I bought it for my NAS in case
I would be updating its operating system not to have it turned off by random
power loss.

I had issues with power supply to my apartment once in 2 years or something
like that.

This model has "controlled by master" outlets which I did not use because I
needed only backup lines connected to battery. That "controlled by master"
thing would turn on once in 3 months without reason.

Then one day there was no power loss and UPS flipped and turned off power to
my NAS and to my devices. Battery was good power was there but switches
flipped and my NAS was turned off without warning. There was no system
updates, maybe just normal writes to the disk.

Turned out my HDD WD-RED 1TB died because of that one flip. It would have been
better for me not to have a UPS...

~~~
christefano
I’m sorry for your loss.

It sounds like you used a Back-UPS unit instead of a Smart-UPS, which I’ve
heard switches to battery 10x faster than the Back-UPS.

After learning this I won’t use a Back-UPS for anything where meaningful data
loss might happen. They’re great for lights, cable modems, WiFi routers, etc.,
though.

~~~
ozim
Thanks, it was just a faulty unit that I trusted too much.

I was doing turn off tests with my NAS attached and it was switching correctly
and NAS was not going down, I had couple RPis connected also not going down
and notifications from NUT were in logs. Where my NAS was NUT server and RPis
had NUT client.

It was that one day when UPS malfunctioned in a bad time. Where my electricity
provider was more reliable than UPS I owned. So bad risk management on my
side.

------
watersb
I had an APC UPS battery age out on me, after only a couple of months after
purchase. Back-UPS XS 1500.

I called their customer support, and they asked about the kind of equipment I
had plugged into it.

My main NAS motherboard had died, and I hadn’t gotten around to the full
rebuild that was going to require. So I had ended up with about five or six
cheap USB external drives, with those “wall wart” DC power supplies, strung
along a couple of power strips that were plugged into the UPS. That plus a
27-inch iMac.

It was generally not much power - not much surge to spin up, or to power up
the Mac, and of course at idle was less than 100 Watts.

APC Customer Support said that the power strips might actually be weirding out
the battery.

They sent me a replacement battery at no charge, and suggested that I go with
a Smart-UPS, with their Power Distribution Units if I needed more outlets.

I had always thought the rack-mount PDUs were a silly expensive replacement
for a no-name power strip. But I had long had a keen interest in this sort of
IT equipment fail, after witnessing some spectacular crazy failures in
corporate, and losing the manuscript while I was writing a book on small-
office IT practice.

So I bought a basic PDU, and a Smart-UPS rated at something like 700 VA.

That has been rock solid. Even better than a larger setup I had with some big
CyberPower systems.

I’m willing to go along with the cargo-cult of PDUs now. I would be quite
surprised if there were any significant difference among the basic PDUs of
well-known brands.

I still have those USB drives. They’ve lasted about as long as the hamsters,
not as long as the dogs.

~~~
rsync
"APC Customer Support said that the power strips might actually be weirding
out the battery."

I think it's more likely that you purchased a guerilla-remanufactured unit
that was properly sealed and packaged to look brand new (with hologram
stickers and anti-tamper seals, etc.) but had an old, already dead battery
that was reconditioned just enough to last a few cycles after purchase.

Did you buy this directly from APC ?

~~~
watersb
I don't recall the vendor but I believe I purchased the original Back UPS via
Amazon. So, perhaps not quite the best.

I bought the SmartUPS and PDUs from an authorized dealer that APC Customer
Support referred me to.

That worked out better.

------
firekvz
I have 4-5 hours outages every day, I use 2 APC ups to keep my modem and
router up, while I still work with my laptop.

It works perfectly for me, these APC devices have given me at the very least
1500 hours of continuos internet access where I could work or entertain myself
during the outages over the last 4 years, so I think the 180$ per unit it
cost, was a pretty good investment in my case

~~~
bowmessage
I'm surprised to see that if the power is out in your area, that the power
used to boost coax signals in your area is not out as well!

~~~
jcrawfordor
If the cable provider offers digital voice, they're required to have backup
power for their infrastructure for at least 24 hours (or 8 hours under older
regs) to allow for 911 calls. The power injectors used for cable amplifiers
usually just have a couple of lead-acid batteries in them.

~~~
hackmiester
Just because they are required to do it, doesn't mean they do it. My source is
experience.

------
francis_t_catte
Two things about Lead-Acid or AGM based UPS's (regardless of UPS topology or
design):

1.) check your battery health annually and replace bi-annually. I don't care
about the battery quality, an always-online UPS is very hard on lead-based
batteries. they're float charged basically all the time, and deep discharged
during outages. if you're in a power failure prone area (i.e. more than one
per year), invest in a generator too in order to avoid stressing the batteries
with full discharges.

2.) check the battery float voltage with an actual volt meter to make sure the
UPS is calibrated correctly. APC UPS's in particular, prior to and post the
Schneider Electric buyout, had a lot of really poor cost-savings decisions
applied to their enginnering. this included using a carbon film resistor-based
voltage divider to measure the battery voltage on much (or all) of their Back-
UPS and Smart-UPS range. if you don't know anything about resistor technology,
carbon film resistors (especially cheap ones!) change in value due to
temperature, humidity, and age, usually drifting up in resistance. this is a
bad thing when you need a stable voltage reading...

oh and on APC's cost cutting measures; there's the fun time they stopped using
nickel plating on the bus bars in their Symmetra UPS line. they switched to
tin plating instead. apparently none of them had heard of tin whiskers. :)

~~~
extrapickles
Some APC UPSs will check battery health _monthly_ by switching to battery, and
letting them run down. You will want to disable this feature as it takes
6-8hrs to recharge to full, leaving a massive random gap in coverage. This
also puts undue wear on the batteries as they are only good for a dozen or two
cycles.

------
kop316
> I live in a place where blackouts are very infrequent (perhaps a couple per
> year), but occasionally the mains drops out for only a second or two. I
> suspect these very short dropouts occur when substation switchgear operates,
> but have no way of being sure. Anyway, with a server running 24/7 I
> obviously wanted protection against any loss of the mains supply.

> So I thought I had covered all bases, and, indeed, the UPS proved useful on
> several occasions. I would quite often be on a work trip and receive an
> e-mail from the server informing me that mains power to the UPS had been
> lost, then another e-mail soon after informing me that mains power to the
> UPS had returned. Only once did the power cut last longer than the battery
> capacity, and the server was shutdown automatically.

It sounds like the UPS is doing exactly what he wants it to do. This is
exactly why I bought a UPS. I would have power transients sometimes and
rebooting my entire network (with NAS and servers) was annoying, and I didn't
want it to go out when I was gone.

His main complaint is he bought a standby UPS where the battery failed, it
turned off the UPS (which is understandably frustrating), and now replaces the
battery every three years. Looking at the white paper referenced, it even says
to go for Line Interactive for servers. I'm also curious how the person knew
that power wasn't cut when he was away?

So other than buying the wrong type of UPS (which at face value looks to be a
valid complain based on research)....why isn't a UPS as useful as they'd
think?

~~~
bluedino
>> His main complaint is he bought a standby UPS where the battery failed, it
turned off the UPS

As a small business network/systems admin, I've had more failed UPS's bring
things down than I can count. It's very common.

~~~
Covzire
I ran into an extremely perplexing problem a few years ago where shutting down
one server connected to a UPS would kill the entire network until the server
was brought up again. The server was not providing any kind of networking at
all, no DNS, DHCP, routing, etc.

After wasting a lot of time remotely trying to diagnose this, it was obvious
what was happening once I got on site. It turned out that once this server was
shut down, the UPS didn't have enough power draw to power the other equipment
attached to it, so a switch that was plugged into the same UPS would shut down
as well. For some reason it had failed in such a way that it required a
certain level of draw for it to function at all.

~~~
jaywalk
Some UPSes have a special outlet on them that when it's not drawing power, it
intentionally shuts off the other ports. It's meant for power saving, but I've
seen more than one person get tripped up by this functionality.

------
popotamonga
Worst part about UPS that i didn't know was:

The constant humming (no fan, just electrical) so cant sleep in same room

The loud can't turn it off beeps when power is out.

And none of those come in the product description.

~~~
SyneRyder
There is a way to turn off the beeps on the APC UPS line (at least the ES 700
I have), but it involves installing software that comes with it onto a Windows
machine, connecting to the UPS via USB and changing the settings.

It's enough of a pain to do that rather than configure all 3 UPS devices in my
house, I've only ever gotten around to doing it on one.

Can't say I've noticed the electrical hum, except during a blackout. But I
don't have mine in a bedroom.

~~~
_rs
Newer models have a button you can press and hold to toggle the alarms without
plugging into a computer.

------
lini
The explanation of the failure was very strange to me. I know there are three
main UPS types - offline, line interactive, and online. Offline types have the
battery disconnected until there is a power outage and only use it when
needed. Line interactive and online use the battery more often to absorb power
spikes, brownouts, and other anomalies. These two types also use the battery
more and need replacements more often than offline UPS.

I have been using the same offline UPS and battery for the last 7 years and it
is still working fine - a few days ago it handled a 15 min power outage with
50% of the battery.

Can someone explain why offline UPS can fail if the battery dies? Is it by
design or a manufacturer specific issue (e.g. only APC brand ones do this)?

~~~
kop316
Re-reading I was thinking the same thing. Batteries don't just "die", they
degrade in performance.

How did he also know power didn't go out too? That confused me as well.

~~~
danilocesar
because he gets emails from the unit when it happens.

I had a script in a raspberry pooling my UPS each minute asking if the unit
was running on AC or battery, and dropping that info into a file when it
changed. I know the software/daemon can also do something like that.

~~~
jaywalk
Yes, but in this case he wouldn't have gotten an email since the UPS failed
right when the power went out.

I actually had the exact same thing happen to me a few months ago. A power
flicker so brief that it didn't even reset any of my clocks, but it caused one
of my cheapo standby UPSes to give out.

------
ramshanker
One thing I always wonder about these home server is this. When you are
leaving house for a long vacation, is it really safe to leave some electrical
appliances working? Aren’t people afraid of fire hazard. What if there is a
short circuit while you are away. A smelling short circuit would definitely
burn something if left unattended for few days.

For once there was a high voltage fault in my neighbourhood, destroying few
lights, all mobile chargers plugged in and microwave left in standby. Had I
not been home, and fault lasting more than 5min, things might have gone really
bad.

Now on, Whenever I leave my home for long duration, I just empty the
Refrigerator and switch the house mains supply off before loving the house.

~~~
reaperducer
_One thing I always wonder about these home server is this. When you are
leaving house for a long vacation, is it really safe to leave some electrical
appliances working?_

I used to feel this way, but then I realized that the electronic devices don't
know I'm away on vacation, or when I've returned, and they're just as likely
to start a fire when I'm down the street getting coffee as on the other side
of the planet. And when I return, my presence doesn't magically reset some
catastrophe timer and everything's all better because I touched "base."

That said, if I'm gone from home long enough that I turn off (or down) the
refrigerator, then I'll unplug everything. So I guess I'm still a bit
paranoid.

~~~
outworlder
There are failure conditions that are not immediately catastrophic. The
reasoning being that if you come home after a work day (or even better, after
coming back from your coffee down the street) and see that a device
malfunctioned you will attend to it. As opposed to leaving it plugged in and
turned on for weeks while you are not there.

A lot of devices will smoke before starting a fire, sometimes for quite a
while until temps increase sufficiently for ignition. You would smell the
smoke and figure out the culprit.

Turning off everything is still worthwhile while you are away. This is just
risk management. It is a small risk (maybe you have faulty appliances or house
wiring? maybe you live in an earthquake or tornado area? etc) but the
mitigation is also not very inconvenient.

That said, if you can have a smoke detector pinging you (or a similar device -
Amazon's cameras have a microphone that can alert you to alarms) it would be
better. As you point out, stuff could happen while you are temporarily outside
the home.

------
lsllc
Like the author, I rarely see power interruptions that last more than a second
or two (unless there's a major snowstorm or something).

It's kind of annoying and I'd love to see a solution that isn't just "get a
battery based UPS" \-- maybe something capacitor based, enough for say 15-30
seconds?

I guess I could get a flywheel [0], but I don't think it'd fit in my basement.

[0] [https://www.vertiv.com/en-
us/products/brands/liebert/?id=59](https://www.vertiv.com/en-
us/products/brands/liebert/?id=59)

~~~
pacaro
Back in the late 90s I had a PC motherboard that had a capacitor for exactly
this. I could (if i was quick) change which outlet the pc was plugged into
without loss of uptime

~~~
zantana
I also remember a green pc set up which used one of the low power x86 clones
(Via?) in the 90s which used the bios battery double as a mini ups similar to
that.

------
sparc24
I ended up in India during the lockdown. Power outages are frequent and so are
voltage fluctuations. Most people have a generator. Most houses haves 3 phase
power coming in. Basically anything over 3 kvA the utility guys put in 3 phase
at 415V - 3 hot and a neutral. About 3 weeks ago we lost neutral which
resulted in double voltage both my MBP chargers got fried including the long
extension wires which are super useful. It also took out an AC, a
refrigerator, 2 air purifiers. Anything connected to the BackUPS did survive
including the 65" oled tv. Luckily we managed to fix all of fit with simply
replacing the PCBs. Being stranded with my laptops would really have sucked.

Since I am stuck here til next July I started fixing some of this. More than
anything else power conditioning was the single most important thing. Anything
with any reasonable switch-mode power supply will be fine on a line
interactive UPS, most people don't need to spend $ on an online UPS - esp if
your power is fairly clean. We had old locally made generator so I finally
replaced that with a nice single phase 25kVA generator. The alternator has
voltage regulation. For the mains power I was told most people just put a
Servo Stabilizer but I didn't want any moving parts so found an IGBT based
static stabilizer instead.

[http://anjalipowersystem.com/static-
stabilizer.html](http://anjalipowersystem.com/static-stabilizer.html)
[https://download.schneider-
electric.com/files?p_File_Name=JS...](https://download.schneider-
electric.com/files?p_File_Name=JSII-5YQSBR_R1_EN.pdf&p_Doc_Ref=SPD_JSII-5YQSBR_EN)

~~~
unholythree
Get phase monitors for your condensing units. There’s nothing more annoying
than loosing a compressor due to your poco’s incompetence when the compressor
would be just fine if something locked it out as soon as the power got weird.

I did a compressor change out on a package system last year because while we
apparently sprung for all sorts of other “options” on the machine apparently
the line was drawn on a $48 phase monitor. Our cheaper machines had them and
rode out our service being single phased, and the package units stage two was
thankfully off at the time; but we still had few thousand dollars of
compressor needlessly converted to a piece of scrap metal.

------
EricE
I'm not sure line-interactive UPSs will guarantee a change in behavior in and
of themselves since they are still stand-by UPS's but instead of cutting over
to battery when in an over or under-voltage situation they attempt to correct
it first.

For critical loads where I don't want interruption I prefer online or double-
conversion UPS's. Basically they have two inverters instead of one. The load
runs off of battery constantly on the first inverter, and the second
continuously charges the batteries. There is no cut over time when there is
mains power interruption since the loads run from batteries.

But I hadn't considered this dead battery scenario so that's another thing to
add to the checklist of things to ask about. It seems that there should be a
bypass mode if there is mains power to supply power to the load too all the
time.

I've found UPS's to be a mixed blessing - when the power does glitch they can
save your bacon but the battery maintenance issue can cause their own outages.
If I lived in Florida with their legendary lightning I'd just put up with it
but I used to have UPSs on everything and these days I have really dropped
down where I have them since we get maybe an outage a year and glitches are
equally infrequent too.

------
nippoo
Where I live (in the UK) the power is reliable enough (one outage every 3-5
years) that I only tend to spec UPSs for devices with dual PSUs - one raw
mains, one UPS-protected. I've had more UPS failures than mains failures in
the past decade... and mains power will normally come back up, starting the
equipment automatically, while failed UPSs generally require manual
intervention to fix, and consequently much greater downtime...

------
dragontamer
> While I was away from home on a long work trip, suddenly I could no longer
> connect to my server and I had not received an e-mail from the server
> informing me of any problem. Luckily it was near the end of my trip so I was
> not too inconvenienced. When I arrived home I found that the UPS was
> sounding an alarm and was not supplying power to the server even though
> there was mains supply to the UPS. It transpired that the UPS battery had
> suddenly died without warning and could no longer hold a charge, and this
> had happened while there was mains supply to the UPS, i.e. there had not
> been a power cut while I was away. Fortunately there was no loss of data on
> the server; I was able to run fsck during boot-up.

And this is why professional servers have two, redundant, power supplies.

If you had two power supplies, the UPS would fail, but you'd continue to
function off of mains voltage.

UPS can fail. Mains can fail. Two power supplies hooked up two both powering
your server redundantly means you'll only fail if both fail simultaneously.

~~~
mprovost
That doesn't protect against surges though - any weirdness from the mains
power would still fry your server through the unprotected power supply.

~~~
dragontamer
Surge protectors are pretty cheap, and I generally assume that all expensive
equipment would use them when connecting to mains.

~~~
adrianmonk
Also, surge protectors wear out and should be replaced before they lose the
ability to protect.

This will probably occur at a different time than when the UPS wears out, so
it could be beneficial to keep them separate so you can replace the surge
protector only.

------
russellendicott
I recall from my years as a small business sysadmin that some of the Smart-UPS
systems that have a serial connector for management access require a special
serial cable. If you plug in a “standard” serial cable it cuts power to the
whole UPS unit and your whole server rack loses power even if the batteries
are fully charged. That was a bad day.

~~~
jlgaddis
Indeed. I, too, learned that lesson the hard way many, many years ago! I also
know several other folks who learned that the same way that you and I did.

Although I'm a bit "old school" and generally prefer serial (RS-232) ports,
this is one case where the change to USB really was a huge improvement!

~~~
quercusa
Yep, sometimes there's nothing as loud as silence!

------
EvanAnderson
My experience has been that inexpensive UPS units create more problems than
they solve in the long-run. Spending more money up front to get a corporate-
production-grade unit is worth the money.

~~~
olyjohn
This exactly. If your power only goes out once or twice a year, your crappy
UPS is more likely to fail before it proves any value.

------
AnonHP
One of the annoying things I’ve seen with the Back-UPS range from APC is that
they all seem to have an audible alarm when it’s running on battery that
cannot be turned off. The UPS will beep periodically until you either turn the
UPS off or until mains power returns. This is so annoying that you can find
instructions and videos online on how to perform a surgery on the UPS to
disconnect the buzzer from the rest of the circuitry.

Maybe APC really wants to drive users of its lower tier (and cheaper) UPSes
mad with the beeps and force them to buy the more expensive Smart-UPS range
that comes with a built-in option to turn off audible alarms.

Well, audible alarms do have a place in such systems to inform the person that
the connected devices or systems are running on a limited battery capacity.
But forcing that at all times is a big annoyance.

~~~
somehnguy
During an extended power outage years ago I used my Back-UPS to keep my phone
charged while I watched Netflix over cellular. I ended up wrapping the thing
in a whole bunch of blankets and towels to muffle the obnoxious beeping. Huge
oversight that there isn't any button to silence the alarm, there are plenty
of reasons someone would want to do it.

I meant to tear it apart and remove the beeper after that but never got around
to it before the battery made it useless anyway. TBF it was a few years old at
that point so the battery giving up wasn't unexpected.

~~~
somehnguy
I'm really curious why this got negative points.

------
hinkley
As we were growing, we slowly converted a telco hardware server room into a
real server room. Knocked out a wall to get enough room volume for a mini-
split AC, removing the sprinkler head, moving the servers... And replaced all
the wiring with plugs higher on the wall so that flooding wouldn't result in
an electrical fire.

So when it came time to move our staging database over to the new wiring, the
head of IT unplugged the UPS from the wall, the UPS complains like UPSes are
wont to do in such situations, and in the time it took him to untangle the
cable and plug it into the new circuit, the UPS dies. Bad batteries that the
health checks didn't detect. Unplanned shutdown of our shared database. Whups.

And that is when management was taught about redundant power supplies, and
periodic UPS maintenance.

~~~
dervjd
_|And that is when management was taught about redundant power supplies, and
periodic UPS maintenance._

And hopefully about setting up monitoring on your UPS to keep track of battery
health ;)

~~~
hinkley
The UPS was reporting as green. Not so much you can do when the hardware is
lying to you.

------
mm89
I also have an APC Back-UPS. Mine are the Back-UPS 650 model, I have two of
them. Both emit an annoying LOUD high-frequency capacitor whirring noise that
is audible to my ears even when the loud AC intake fan is blowing in the same
room. I'm actually shocked any company would ship a product in this condition,
unless all their customers have hearing problems. It's a power strip... it's
supposed to be silent. Not like a computer.

If my batteries die, I'll just replace them with non-battery backup strips.
Not worth the trouble for me living in a city where power goes out maybe once
per year on average for 10 minutes, and I don't have servers that need to stay
online anymore.

------
jgeada
After many horror stories with APC UPSes:

\- failed battery caused APC to stop operating even with power (just as in the
original post)

\- stopped charging battery even though battery was still good (blow
electrolytic cap. When I into the circuit that capacitor was rated for 14V on
a 12V trace, ie no guard-band. Seriously, skimping on maybe $0.01 total parts
cost to leave a system at risk of fire??? Who the heck signed on on that
decision???)

\- couple of data center APC UPSes caught fire. On the plus side the emergency
systems kicked in quickly enough that the only damage were the UPSes.

Anyway, that was a few too many stupid failures. APC is on my "never ever
buying from this company ever again" list.

------
tx-kun
I was doing some researches about this very topic a couple of weeks ago and
saw a post on Speciesworks (still trying to find the post). In that post, one
Eaton rep replied that the ups device would shut down once the battery died to
protect the devices connected to it.

Teah, it's just this simple. This is just a byproduct so all those companies
can boast their insurance coverage on damaged equipment you connected to their
UPS. And guess what, most of the time you won't be able to get this insurance
even if your stuff got fried, saw a few stories like these from recent
Slickdelas posts of UPS.

------
Havoc
Generally line interactive is less preferable since they provide less
protection from surges than a double conversion setup. Big price difference
though so line interactive is usually a reasonable compromise.

~~~
snuxoll
For a home setup you aren’t going to be spending the money a double or delta
conversion unit costs, so line-interactive is the only sane choice.

You really don’t want line-interactive gear when dealing with larger loads
either, as the transformer will just cause extra current draw during a voltage
sag. This is why you don’t see (many of) them above 3-5KVA.

------
m463
I wonder if the tesla powerwall acts as a UPS.

EDIT: I found an interesting thread about the powerwall, switchover and using
a UPS:

[https://teslamotorsclub.com/tmc/threads/powerwall-2-ups-
conn...](https://teslamotorsclub.com/tmc/threads/powerwall-2-ups-connundrum-
and-solution.130085/)

it appears the powerwall moves the line frequency up from 60hz to as much as
65 hz as a signal to the solar power inverters and that can trip up some UPSs
which monitor 60hz as an indicator of "good power"

------
gerdesj
"I live in a place where blackouts are very infrequent (perhaps a couple per
year)"

I live in a fairly rural place (Somerset, UK) In this particular part of the
county, outages are approaching "per demi-decade". A recent boiler room
explosion in a BT phone exchange caused my office to lose power for about 10
hours but my home, which is about a mile away, was fine. I kept the genny
topped up at regular intervals. The many but small UPSs we use keep things
running for the 10-20s that the genny needs to fire up and settle.

At home I have several small UPSs to keep things running for about 45-60
minutes. The esxi (Dell T320) in the attic gets shutdown after five mins so
that everything else up there gets more time.

Anyway, its all about risk assessment, monitoring and understanding your gear.
A Back-UPS is not the same as a Smart-UPS - output waveform and response to
load etc. Also, your UPS should be self testing every two weeks. I have
several APC Smart UPS 1500VA and others. The 1500 jobbies are something like
15 years old but on their third set of batteries at least. When apcupsd whines
that they are getting on a bit we buy new batteries and swap them in on-line.

My golden rule of thumb is do not buy a battery from a firm that you do not
recognise. Do not skimp and save pennies over something that can explode or
simply be rubbish.

------
epc
Buy an automatic transfer switch. Plug one input into a UPS, plug the other
into either the mains or another UPS (preferably a different brand but
identical power). I resorted to this after having multiple APC and Cyberpower
batteries fail killing power (even with a line-interactive APC). I run my
network (cable modem, router, primary eero AP) off this, no servers. Means we
can typically stay online even when the power glitches for an hour or two
after a storm.

~~~
_rs
Do they make these that have normal 5-15R plugs on them that don't need custom
wiring?

~~~
epc
The one I bought uses standard NEMA cords and outlets: "CyberPower PDU15M10AT
Metered ATS PDU"
[https://www.amazon.com/gp/product/B00NEHUX08/](https://www.amazon.com/gp/product/B00NEHUX08/)
— it’s overkill for my use case but was the smallest option I could find. I
don't have any of the control modules (provide snmp/http APIs).

------
eigthbits
I found this guide by Cyberpower to be a clear and concise explanation of the
topologies of UPS offered and their benefits. Yes it's content marketing, but
it's good.

[https://www.cyberpowersystems.com/resources/choosing-an-
unin...](https://www.cyberpowersystems.com/resources/choosing-an-
uninterruptible-power-supply-system/)

------
samcheng
With all of the recent advances in Lithium-type battery tech (e.g. 18650) it
seems like a market opportunity to create a new, modern, small, smart UPS.

These low-end APC dinosaurs still use lead acid, and in my experience (with a
solid utility over the past decade) outages are just as likely to be caused by
battery failure than some kind of actual power outage.

If anyone wants to build something better, happy to chat further.

~~~
floatrock
Main advantage of lithium-ion over lead acid is lithium-ion is more energy
dense so you can have a smaller size at a smaller weight. Important if you're
building cars, but the price premium probably isn't worth it if you're
building another office box at commodity pricing.

Edit: Since we're armchair-building for a predictable, high-uptime
application, failure modes might have an interesting advantage though. Any
battery engineers know if lithium ion has more predictable or measurable
failure modes? Yes, we've all seen the exploding hoverboards... I'm assuming
theoretically well-built electronics.

~~~
martinflack
It could possibly target the "Apple-esque" product category by using a smaller
physical footprint to emphasize sleek looks, perhaps with a small sharp
readout. The small size could be leveraged further by only attempting to
provide power for a short amount of time, say 10 minutes, emphasizing and
_requiring_ USB connectivity to shutdown the protected computer at minute 9.

------
linsomniac
Automatic Transfer Switches feel like a requirement for using UPSes to me now.
Either that or redundant power supplies. I've had too many UPSes, both the
BackUPS and the higher end SmartUPS, cause more downtime than they prevented,
over around the last decade.

When we moved offices 3 years ago I pulled our UPSes out, because all the
outages the previous 5 years were caused by the UPSes.

~~~
Johnny555
But then your ATS becomes another potential point of failure. If you have so
little trust in your UPS that you need an ATS behind it, I think you are
probably better off without the UPS's.

In my last job I had around 100 APS SmartUPS's (mostly 3KVA) in various wiring
closets and in the ~3 years that I was there, none of them failed
unexpectedly, but we had to replace a few batteries and/or entire units when
they failed their monthly self check.

~~~
linsomniac
Sure, but I've never had one of those ATSes fail. For a sample size of ~15
over a decade. Where I've pretty much had every APC BackUPS and SmartUPS
(mostly 1500RM 2U, some 3000 3(?)U, some 2200 floor units) drop power at some
point. That includes being very liberal with battery replacement, the last one
was <3 months with a new battery. I would say that they seem to be reliable
within 3 years, It's outside of that 3 years that I've had problems.

------
pcdoodle
Dell latitude laptops have OEM chargers that can run on 10-16VDC. The E6520 I
use as a server takes about 6W to run at idle. Grab a 12V battery and a 5A SLA
Charger, run your router/modem/server directly off the battery.

UPS's take about 10W to just power the inverter. This gives up a lot of the
battery capacity not to mention the losses from converting your power 2 times.

------
mrslave
The biggest value my UPS gave was keeping the home broadband running (modem &
wifi) in a sustained black-out. It impressed everyone a lot, except me.

Keeping a whole system running for a while was my real intention, but I
quickly learnt there were real shortcomings with my no-name brand purchase.

------
linsomniac
Anyone used those new LiPo UPSes? Wondering if they have a longer useful life
than the lead acid, but haven't used them. Thought about getting a PowerWall
for our new office, but they don't start providing power for 3-5 seconds after
the utility power goes out.

------
hrishios
If you're ever inclined, lead acid batteries can be easy to repair and
diagnose lifetime for - depending on the type. Sealed ones are harder but not
impossible. Open ones take a little more maintenance but have long lifetimes
and practically indestructible if you service them often.

The most common cause of death is sulfate build-up, which can be prevented
(and often reversed) with a homebrew circuit[1].

1\.
[https://batteryuniversity.com/learn/article/sulfation_and_ho...](https://batteryuniversity.com/learn/article/sulfation_and_how_to_prevent_it#:~:text=If%20a%20battery%20is%20serviced,block\)%20for%20about%2024%20hours).

------
spookware
I work on these all the time. Problem is normally cheap charger. Try and find
a ups that puts load on the batteries everyonce and a while. Good luck. This
is hard and never done. We got sick of UPS sitting there for sometimes years
and then when needed - batteries collapse and the whole thing comes crashing
down.

I have worked on UPS that are in charge of maintaining power to DP systems.
When they fail you get things like oil rigs pulling off station costing
millions. The company I work for just finished putting batter powered
thrusters on an oil rig. First one ever.

Don't have a job right now. Rather sad.

------
jlgaddis
PSA: When it comes time to replace your APC UPS batteries, check if you have a
"Batteries Plus" (or similar) franchise in your area (in the U.S., at least).

You can purchase replacement batteries from them for roughly half the price!

~~~
AdrianB1
In Europe, I buy the batteries from the factory and they ask for the old
batteries in return; this way the price is lower and I have no problems
recycling the old batteries, they are shipped to the factory (a few hundreds
km away), dismantled for parts (lead, mostly) and used to build new ones.

------
securepower_io
"All UPS systems require regular intervals of maintenance. The availability of
a system configuration is dependent on its level of immunity to equipment
failure, and the inherent ability to perform regular maintenance, and routine
testing while maintaining the critical load. As the configuration goes higher
on the scale of availability, the cost also increases." (APC White Paper 75)

------
guerby
If your devices are low power like a NUC, recycled laptop, DSL/fiber modem or
NAS they'll likely accept 12V as input (or 12-19V for most Intel NUC for
example).

For these I wonder if instead of a UPS: buy two LiFePo 12V batteries with
included BMS, two battery charger (AC to 12V DC), so you get a redudant 12V
bus where to plug your devices.

If above 12V is needed add two DC-DC converters eg 12 to 19V to add a 19V bus.
Same for 5V.

It shoud work and support failure of any one of the parts?

------
noipv4
I weigh my UPS battery every year and compare it to the original weight that I
had printed with a label maker. Over the battery lifetime (2-3 years), there
had been around a dozen switchovers, and the only reason of failure I could
think of is the electrolyte evaporating because of a warm interior of the UPS.
This gives me an idea, of how much water is lost, and at a certain cutoff, I
just replace the battery.

------
WesolyKubeczek
If a power outage is long enough for the battery to go flat, I need to power
on things gradually, or my UPS will act as if overloaded. The stuff I've
plugged in barely amounts to 280W. It's a home lab, so no much harm done, but
also, so much for unattended recovery from failure.

It's good for brief outages caused by thunderstorms, though, so still better
than nothing.

------
neilv
The article correctly and importantly points out that there are many types of
UPS. Most recently, I got a production-grade APC SMX1500RM2U for home.

Another thing to be aware of, if your PC has a PFC power supply, is that it
might reboot or have undefined behavior on event of the switchover to battery,
unless the UPS is designed to avoid this.

------
dstaley
After reading this, I checked what topology my UPS is using and was happy to
see it's line interactive. I have two CyberPower CP1500PFCLCD units, and am
approaching the one year mark. It looks like the batteries are even hot-
swappable, which I'm sure will come in handy when replacing them.

------
mirimir
I've always used line-interactive aka double-conversion UPS. Both because of
the battery failure issue, and to protect equipment from crappy generator
power. Basically there are rectifier and inverter circuits, with batteries on
the DC side.

------
gsich
Some ideas: [https://gitlab.com/esr/upside](https://gitlab.com/esr/upside)

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

------
knorker
Yeah "home quality" UPSs I've found cause more outages than they prevent.

------
beamatronic
I did a lot of research before I bought a UPS. The constant that I saw across
various brands was that these batteries will die after a few years without any
warning. They have to be replaced proactively. No if’s and’s or but’s.

~~~
sliken
I find that true of APC, but not of most other brands (best, triplite,
cyberpower, etc)

APC ships crap batteries and they often do not survive the warranty or die
shortly later.

------
tmp1aa
FYI for the APC Back-UPS "Pro" \- the "Pro" model's topology is line
interactive. (Or at least my Australian 1500 version is, as well as the other
"Pro" models I checked.)

------
gsich
APC deliberately designs their battery case so that the battery will die.

------
dreamcompiler
I suggest building your own UPS with strictly DC outputs. Most of what you'll
be plugging in runs on DC anyway. This does mean you'll need to dig into some
of your equipment to find the DC access point, but on other equipment you'll
only need to cut the wall wart off the end of the cord.

You can choose your own battery and battery maintenance equipment for maximum
longevity, and choose your own switched power supply with different tap points
for different DC voltages.

This is simpler and more reliable than AC line-interactive UPSes because
synchronizing an inverter with wall-socket power is not required. Yes, you
need some EE skills to build it, but the end result will be far more reliable
than a cheap off-the-shelf UPS.

~~~
zzz61831
Yep, and once you start using custom DC UPSes the biggest issue will be
battery chargers that kill lead-acid batteries. Things are better with LiFePO4
these days, but for lead-acid I haven't found a solution except for literally
hacking a pulse charger and battery management on top of arduino.

~~~
dreamcompiler
I've had good luck with solar charge controllers for RVs, e.g. [0]. You have
to drive them with DC of course but they're designed to be driven by very
poorly-regulated DC like that coming from a PV panel. So a cheap AC/DC
converter (either switched or linear) driving one of these things should
preserve your batteries. Most of them also provide a DC load output which gets
automatically switched over to the battery if the input DC (or in the case of
a UPS, the input AC) fails.

[0] [https://www.rvweb.net/best-solar-charge-controllers-for-
rv/](https://www.rvweb.net/best-solar-charge-controllers-for-rv/)

------
colechristensen
TL;DR some UPS systems will shut down power when they detect battery failure
even when mains electricity is working.

~~~
AnIdiotOnTheNet
UPSs, in my experience, quite often have or develop faults that defeat their
purpose. We just threw one out that would cut power entirely during self-test,
but _only_ during self-test, not during an actual outage. I've seen their
battery monitoring circuits fail such that they report a battery as good until
power is cut and then die immediately. The other way also happens, reporting
all batteries as bad even though they might be brand new, so you're never sure
when to replace them.

I've come to the conclusion that if you are going to use a UPS, your equipment
should always be plugged in to at least 2 UPSs, either via redundant power
supplies or an ATS PDU.

------
esaym
Kind of a lame article. He is complaining about his $50 consumer grade UPS.
The minimum any server needs is the Apc SMT750 "Smart-ups". It takes two
batteries, cheap ones last about 3 years, the replacements from APC can last
between 5-7 years. But the unit can supply mains power with no battery
connected and the batteries can be hot swapped easily from the front of the
case. These are $300 new, but you can find them used on ebay between $50-$100.

~~~
amelius
Why is that lame? My smartphone has compute capabilities that come close to my
home PC's, yet it has a battery that's much cheaper than $50.

------
softinio
Funny enough I have been considering getting a UPS. Should I ? If so, any
recommendations?

------
neves
Is it easy to find a battery that fits inside my UPS? Any orientation how to
do it?

------
jpswade
I had this exact same issue with this exact same device. I never replaced it.

------
ChrisMarshallNY
Made me check my two APCs. They are both Line Interactive.

------
nqzero
i've had 2 APC Back-UPS fail (of 2), and in neither case was the battery dead.
That entire line is significantly worse-than-nothing as a backup

------
sytse
tldr; when a cheap UPS battery is failing the UPS will fail even when the main
power is on.

I got personal experience with this failure. Maybe the thinking is that in
case of a power outage you don't want to find out that all your UPS devices
fail at the same time. But in this case a 24 hour warning would have been much
better.

