That UPS you bought for your home server may not be as useful as you think

Some years ago I decided to install a server at home for use as a NAS (network-attached storage) in my home network, and for an Internet-facing server. 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.

I ended up buying a 700VA APC Back-UPS ES-BE700G-UK, which has four mains sockets that are battery-backed and also have surge protection, plus another four mains sockets that have surge protection but are not battery-backed. Additionally, it has two RJ45 sockets to provide pass-through filtering for an Ethernet connection. It also has a USB port for connection to the server so that it can transmit unsolicited status information to the server (including requesting the server to shutdown) and can also be interrogated by the server using the apcaccess command. The APC UPS daemon works with this model of UPS, and was relatively easy to set up. APC, formerly American Power Conversion Corporation, is a subsidiary of European company Schneider Electric. My UPS was manufactured in The Philippines.

I have three devices plugged into the battery-backed sockets on the APC UPS: the server, an external 6TB USB HDD connected to the server for automated daily backups by the server, and a 5-port Ethernet switch. The battery in the UPS would provide between 15 and 20 minutes of power when the mains fails, although I have configured the UPS to trigger the server to shutdown when 30 per cent of the battery power remains, as battery life is reduced considerably if its power is allowed to drain completely. In case you’re wondering why my router is not also plugged into the UPS, due to the position of the broadband provider’s socket the router is in a different room and I have therefore had to connect it to a different UPS, an iLEPO multi-functional DC UPS (the ECO PLUS 412P, which is tiny but can keep the router powered for several hours). Obviously the router needs to be connected to a UPS, otherwise the server would not be able to send me e-mails when there is a mains power cut. Being able to receive UPS status e-mails from the server is important to me when I am away from home on work trips.

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.

Now, the life of the 12-volt lead-acid battery in the APC UPS is supposed to last approximately three to five years. The life will depend on how many times the battery is discharged and ambient temperature.

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.

This failure was annoying on two counts. Firstly, the battery was only about thirteen months old (the manufacturing date stamped on the UPS box was only two or three months before the date I purchased the UPS). Secondly, I certainly did not expect the UPS to stop supplying power to the server while there was mains supply to the UPS. The APC white paper on UPS topologies, ‘The Different Types of UPS Systems‘, does not make this behaviour clear.

It turns out that the type of UPS topology (‘Standby’ — see the model’s Technical Specifications) in this model of UPS does not continue to provide power to connected equipment when the UPS battery either fails or is disconnected for whatever reason when there is mains power supply to the UPS. A quick search of the Web showed me that I was not alone in discovering this ‘feature’: an APC Back-UPS 350 owner posted ‘UPS Battery Backup — useless when the battery dies?‘.

From what I have read, the so-called ‘Line Interactive’ UPS topology does not suffer this shortcoming, so, the next time I have to buy a UPS for a piece of equipment that requires power 24/7, I will buy a line-interactive UPS rather than a standby UPS. But, before purchasing, I will be sure to ask the manufacturer what the precise model would do if its battery fails or is disconnected while there is mains supply to the UPS. The APC line-interactive UPSs are more expensive than the APC Back-UPS models; now I know why. It’s a pity I was not aware of the shortcoming of the Back-UPS models, as I would have spent more and bought a UPS that continues to work when the battery dies while there is mains supply. I would also hope the UPS would issue an alarm if the battery has failed or is disconnected while there is mains supply. Be sure to ask the manufacturer all these questions if you cannot tolerate a sudden loss of power to your equipment if the battery dies while there is mains supply.

Anyway, after checking that the dead battery was indeed useless I replaced it with a new Yuasa battery that has lasted nearly three years now. I will be replacing it shortly as a precaution, even though it has not had to be used much at all since I installed it. I have not replaced the APC Back-UPS model but I will be replacing the battery at least every three years just to be cautious, and of course taking the old batteries to my local waste disposal centre to be recycled properly. By the way, it is possible to purchase a 12-volt battery manufactured by one of the reputable battery manufacturers such as Yuasa with the same specification as the APC battery, for a significantly lower price than APC charges for replacement batteries (which I suspect are badged by APC in any case).


About Fitzcarraldo
A Linux user with an interest in all things technical.

38 Responses to That UPS you bought for your home server may not be as useful as you think

  1. Max says:

    I’m impressed that you count a few power outages a year as infrequent. Where I live (Germany) there is about one per 10 years (so far luckily). I run my main server without a UPS 😉

    • Fitzcarraldo says:

      Sometimes sh*t happens, and it’s sensible to protect against the possibility of data loss due to power outages if your data happens to be important (which, in my case, it most certainly is). The absence of past power outages in your location is not a guarantee that a power outage will never occur in future. According to the following 2019 article from Deutsche Welle about a blackout of more than 30 hours in Berlin:

      Germany’s SAIDI [System Average Interruption Duration Index] score, an average of 12.2 minutes of disruption a year, is a quarter of that of neighboring France, and the federal network agency reported that users were only without electricity for an average of 15 minutes in the whole of 2017.

      So even places in Germany can experience power cuts sometimes.

      • Max says:

        30h only in one district in Berlin “The outage in the Köpenick district of the German capital was unusually long, at over 30 hours, and unusually wide, leaving over 30,000 households and 2,000 businesses without electricity.” (quote from the linked article). Yes I know I’m extremely lucky having a so stable grid here. Not having a UPS is a calculated risk to reduce complexity because and I can’t afford an enterprise grade UPS. I know the limitations of my setup and I know I will have to recover from a power outage in the future.

        • Decade says:

          I feel like I’ve lost more uptime to the UPS than to the power grid here, in San Francisco.

    • yabapolido says:

      Consider yourself lucky, the network might be reliable but there are more variables to consider. Breakers, people plugging in random stuff, short-circuits, etc… Surely that’s not a critical server 😉

    • Alan Williamson says:

      Perhaps 1-2 per year is infrequent – compared to living in some of the Pacific islands where 1-2 per week is common and a UPS is a luxury.

      • Fitzcarraldo says:

        About thirteen years ago I went on a work trip to Delhi, India, and there were several power cuts daily. I recall on one of the days there were eight power cuts. I think the fundamental problem there then was lack of generating capacity. I would hope it’s better these days.

        • N Sathyanarayana says:

          It is much better now; generation is not a big issue but then transmission and transmission losses do result in power cuts. It is not the same throughout the country but I would be surprised if every IT/Software company did not have a huge on-line UPS with a generator to boot. I have a UPS in my apartment that supplies a certain amount of backup power; further backed up be a generator for the complete apartment complex.

          In short it is a much better situation but we cannot ever do without UPS.

  2. Mike S. says:

    I long ago gave up on APC UPS units for this very reason — they fail “silently” without any indication that anything is amiss — UNTIL the power is cut, and only THEN do they let you know that the battery has died some time ago. Useless, and very, VERY bad design for a product that is supposed to be used for mission-critical devices.

    Their status monitoring app does not disclose this, nor is there any indication on the LCD panel of those units with a display.

    So I no longer buy or or recommend APC units, and have been much happier with the CyberPower brand.

    Like APC, low-cost replacement batteries are available for CyberPower units above the low end of their range.

  3. Pingback: That UPS you bought for your home server may not be as useful as you think – Hacker News Robot

  4. Richard Amiss says:

    It’s utterly ridiculous that we have to spend more for what is obviously an instruction to the UPS to shut down if the battery is bad or disconnected. It’s not as if you actually need to shut down a UPS without a battery, you would just be bypassing the battery charging circuit.

  5. Xiao says:

    What I really want to see are more PSUs with integrated UPSes, like this one:

    I’d be curious your thoughts on something like this rather than a full UPS.

    This feels like it saves the cost of the inverter, both in money and power efficiency, and removes all the headache that it introduces. The signaling to the host via the power button connector also seems like a clever touch.

    All I really want is for my home NAS to shut down cleanly in case of power failure, and then power back on when it detects mains power has returned.
    – The latter is available as a feature in many motherboard BIOSes
    – The former unfortunately seems mostly dominated by full UPSes, which seem like overkill to me.

  6. Levi Durham says:

    There is a third kind of UPS, Double conversion. Though a bit priceyer, if you have “dirty” power they can greatly extrend the life of your equipment.

  7. Redundant PSU with one connected to the mains and the other to the UPS is the way to go. And for the UPS itself, always go with online double conversion, accept nothing less.

  8. Ppp says:

    I think the title of your blog is quite unfair, but I respect your opinion. If you have purchase a UPS with a network card that would easily solve your problem. Also, batteries are covered by your warranty. So, you should have easily called APC technical support for assistance and they will gladly replace your batteries at $0.

    • Fitzcarraldo says:

      It’s not unfair at all, because nowhere did I find a warning in the sales literature for that model of UPS stating that mains power to the server would be cut if the battery suddenly dies while there is mains supply to the UPS. As I stated in my blog post, had I been aware of that, I would have bought a line-interactive UPS instead, ergo ‘the UPS I bought for my home server was not as useful as I thought’. If my blog post has given a heads-up to at least one person who did not know that the APC Back-UPS range behaves in that manner, it will have been worth writing. And, actually, having read some of the comments on Hacker News regarding my blog post, several people did not know that.

      How would a UPS with a network card stop a battery that suddenly dies without warning from causing the UPS to cut power to the server while there is mains power supply to the UPS? It’s not a network card per se that would solve my problem; buying a line-interactive (or even more sophisticated topology) UPS rather than a standby-topology UPS would solve my problem. And, as I have written, had I known the limitation of the APC Back-UPS before buying it, I would have bought a line-interactive UPS instead. Hindsight. Also, the cost of the replacement battery is not the issue here; the issue is that failure of the battery causes this model of UPS to cut power to the server when there is mains supply to the UPS. If APC replaced the battery for free that would not change the limitation of that model of UPS, and seemingly all UPSs that use the standby topology. To reiterate, had I known that, I would have invested in a line-interactive UPS instead. Hindsight is a wonderful thing. Hopefully my post will save at least one person from discovering the hard way, as I had to.

  9. Louwrentius says:

    When you buy a new battery, ask for a ‘fresh’ one. They often sit on the shelf for years and lead acid batteries spoil if they are not recharged every 6 months.

    Look at the capacity differences (I tested multiple brands and capacities)

    • Fitzcarraldo says:

      Point taken, although it’s not really practical to ask for a ‘fresh’ one when you order a battery from an online supplier such as Amazon. One can only hope that the online vendor’s stock turnover is sufficiently high. Where I live there is nowhere locally to purchase this type of small 12-volt lead-acid battery over the counter. But I do look for a manufacturing date stamp on the battery when it is delivered by post or courier.

  10. Decade says:

    The line interactive models seem better, but I don’t think the line-interactivity is what makes them better. I have a SMT1500, which is supposed to be line-interactive, but it somehow failed to protect my server during the July 4 fireworks, when the power flickered once. But this week it started beeping to indicate its dead battery, and it hasn’t shut off the power.

    I’m a bit reluctant to replace its battery when it dies. I was looking for how to maximize its runtime, and found this forum posting explaining how APC intentionally programs their UPS to kill batteries early using overly high charging voltage. And then the voltage drifts up over time.

  11. MJ says:

    Don’t knock APC because you bought the wrong unit. If you had educated yourself as to which model to buy you wouldn’t have any problems. Computer equipment virtually always dictates line interactive battery backup. The cheaper units have always been for TVs, answering machines and other type of consumer products.

  12. Lokesh T says:

    Even we have purchased APC BRC 1500 backups series, During installation checked the power supply found good while mains ON, During mains failure it’s giving around 40% variation in power supply as well as earth factor. (Suggested True RMS meters for measuring voltage).
    APC had suggested that we should buy Online pure sinewave UPS for connecting any valuable instruments.
    BRC1000 series were dedicated only for computers.

  13. Philip Oakley says:

    Also check the quality of your electrical supply wiring, as different countries have different approaches to the quality of the supply connection. It’s said that US has a poorer Earth/Neutral quality than Europe (mainly because of it’s size, cable runs, and connection schemes). Earth and Neural bonding issues can also cause supply transients that are not simple ‘loss of power’ that a UPS typically handles. There are plenty of videos, with side comments, by John Holt about the Earthing & Bonding issues.

  14. Nick says:

    But one must also consider that once the battery fails if the UPS stops supplying power your device(s) are protected. Whereas, if they were continued to be powered without that battery backup the sudden loss of power could be detrimental. I’d rather have a UPS stop supplying power rather than have it ‘pull the plug’ when the power drops out

    • Fitzcarraldo says:

      In the event the battery suddenly dies (or has become disconnected for whatever reason) while there is mains supply to the UPS, I’d rather have a UPS that: a) maintains mains supply to the sockets rather than cutting off power to the sockets without warning; b) informs the APC UPS Daemon in the server via the USB cable that the battery has failed and no longer charging. That way, the owner could decide beforehand how to configure the APC UPS Daemon to respond. For example, I have configured the APC UPS Daemon in my server to shutdown the OS and poweroff the server (i.e. not go into hibernation) if the UPS informs it that battery power has dropped to 30 per cent of full capacity. And I have configured my server not to boot automatically if power is restored. Some people do configure their server to boot automatically if power is restored; I chose not to. Basically, what I’m saying is that the UPS could be designed to inform the APC UPS Daemon in the server that there is mains supply to the UPS but the battery is dead and there is therefore no possibility of charging it. After all, this model of Back-UPS can already inform the APC UPS Daemon about various other conditions. If you study the APC UPS Daemon shell scripts you can see that, were a UPS to inform the APC UPS Daemon accordingly, it would be straightforward to create a shell script to do whatever the server’s owner requires to happen.

    • Alex Atkin says:

      I think you are missing the point. The UPS cut-off the power without warning, potentially causing corruption. If it had carried on running but without battery backup, there would have been the “potential” for a power failure to do the same, but the odds are it wouldn’t have.

      So by having the UPS shut down on a failed battery, its increasing the odds of data loss and damage rather than its very purpose of reducing it.

  15. kusanagisama says:

    I have an APC 650ES UPC, the supplied battery apparently started failing self tests after two years of ownership, but I waited until this year (3 years after initial self test failure alarm) when it started shutting off during the self tests.

    I could never get more than 5 minutes of runtime with that battery. I went to Batteries+Bulbs to buy a Duracell 9Ah battery. I now get up to 15 minutes of runtime. I also uninstalled the APC software, and I’m letting Windows handle the APC.

  16. Jeff says:

    I only let my UPS drain 5 to 10% before shutdown. This covers most short Power losses And prevents deep drain from the battery. The bios is set to “always on” so that as soon as the UPS has restored the computer reboots. I live in Florida and we have frequent outages and have found that if UPS is allowed to substantially drain, the battery life is extremely short. I try to size the UPS so that it in theory could have a one hour run time. Line active is the best choice but they are super expensive and since I have three separate computers and a router in different locations it would be very expensive without a centrally wired UPS.

  17. Clive Lumb says:

    I gave up on APC a long time ago. I have had both domestic style and 2000kVA proper server rack models. NONE of them looked after the batteries properly. ALL of them failed miserably with no warning.

  18. Darin says:

    Just stay away from APC in general. If you’ve ever had to file a claim with them, they make you jump through an insane number of hoops, all while making you feel like you’re trying to scam them. I’ve had much better support from Phillips and Tripplite. As an example, I have a Smart1500LCDT on my server rack. I’ve changed the batteries once and they lasted about 4 years as I recall. Never had issue with my server on it.

  19. Mauro says:

    That’s strange… I own three APC Back-UPS ES-BE700G-IT, the two oldest ones did require their batteries to be replaced (after many years of operating), however when the old batteries went bad a sound alarm was given by the UPS units, while attached devices kept on working. I did not experience any power cut at all… Perhaps my batteries were not damaged, but simply exhausted.
    I must confess I’m really happy with these APC UPS units…

    • Louwrentius says:

      I have also good experiences with APS gear both privately and professionally.

      I’ve even done an online battery replacement on the pro gear.

  20. Mike Nelson says:

    I have just got in the habit of replacing UPS batteries annually. It’s a small price to pay for a bit more piece of mind.

  21. James A Macdonald says:

    You didn’t indicate what size power supply your server power supply is; that could explain why your battery died so quickly.

    I had an APC 1400VA Smart-UPS for many years (approx. 2002-2013).

    I found out the hard way; I went from a tower to a Z-800 workstation with an 1100W PS. The PS is rated at 90% efficient and I figured that it should be adequate for the new machine. It was until I put a 2nd processor in it. That killed the UPS.

    Subsequently, I found out that HP recommends a 220 VA UP for use with the Z800.

    • Fitzcarraldo says:

      That is unlikely to be the reason in my case. The server’s input power requirement for its 150W power supply is 185W, and the UPS is rated at 405W / 700VA. Also, having replaced the dead battery with a battery of the same type, size and specification (12V 7Ah), the replacement battery has not failed in the nearly three years since and the APC UPS Daemon’s apcaccess command reports no problems with the battery or the UPS itself.

  22. “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)

    Enterprise servers are typically dual-corded, but if your server is single-corded, then a rack ATS can provide additional availability. APC’s rack ATSs are compatible with Double Conversion On-Line UPS only–Double Conversion On-Line is the UPS architecture typically found in server rooms. For even more availability, you can add a generator or two into the configuration. A full dual-path architecture can provide up to 10,000 times less downtime than a single path design (APC White Paper 48).

    APC’s worldwide support phone number is 1-800-555-2725. APC by Schneider Electric warrants its products to be free from defects in materials and workmanship for a period of two years from the date of purchase. Please note that APC has discontinued this UPS, and newer, more advanced models are available.

    For additional information, please reference APC White Paper 280: Practical Guide to Ensuring Availability at Edge Computing Sites.

    • Fitzcarraldo says:

      Please note that APC has discontinued this UPS, and newer, more advanced models are available.

      In which case, as you’re an APC reseller, perhaps you should tell APC to stop selling the discontinued UPS via Amazon:

  23. Vincent says:

    APC (like any other M*F* on the market) makes “horrible” item for normal price, “medium” item for high price and “excellent” item for ENORMOUS price. F*** all of ’em! So I’m not surprised any even “average” goods are total cr***p. Find the guy who can “modify” your UPS (or make brand new) – then you can be sure it works.
    BTW it’s not necessary to make DC->AC in UPS, then AC->DC in ATX. There is “direct supply” DC->DC from battery to motherboard.

  24. Lars Poulsen says:

    In my small business I installed a Tripp-Lite 2 KVA Interactive UPS. I have discovered that every couple of weeks (interval has varied from 24 hours to 3 months) something happening in the light industrial building sends a surge down the wire that causes the microprocessor in our UPS to lock up. The light display seems to indicate “battery overvoltage”, The result is that the UPS is beeping loudly, and it requires an extensive reset to clear. (Disconnect line power, disconnect the batteries, then reconnect batteries, reonnect line power and bring the 3 servers in the rack up again. I knew that we might have occasional power spikes, that was WHY I installed a top of the line UPS.
    Tripp-Lite was not very helpful: The unit is out of warranty. If it had been in warranty, we would have shipped you a replacement.
    SO I bought a new UPS, but kept the old expansion battery bank. 10 days later, the new unit crapped out. This time, the lockup caused it to stop charging the batteries, and when the battery ran way down (16 Volt reading on 24 Volt battery pack) the servers went down.

    So higher grade UPS does not always solve the problem.
    I am thinking of putting a constant voltage transformer in front of the UPS.

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