Modern UPSs: Their creative control schemes and power sources

Within my mid-2023 teardown of a malcontent APC Back-UPS ES BE550G 550VA UPS, I wrote:

What I like about these units (and conceptually similar ones from both APC and competitors) is that the batteries are user-replaceable, and they’re standard-size and -spec. A SLA (sealed lead acid) [editor note: a correction from the original “Ni-Cd” per reader feedback] cell will sooner-or-later go kaput, whether it’s due to repeated premises power loss dependency on it or just extended trickle-charging-induced storage-capability decay, but you can then just pop in a replacement battery, and it’ll be good as new.

Increasingly nowadays, however, I’m learning that this longstanding assumption of battery standardization is unfortunately falling by the wayside. Take the Amazon Basics ABST600 600VA UPS that I replaced the BE550G with:

I got it as a backup in the first place because it was an Amazon Warehouse-sourced open box unit sold at a $20 discount from the brand-new price and ended up looking (and working) like brand new, too. But, although Internet research confirmed that it was a rebranded CyberPower unit, it turned out to use a non-standard 12V 5Ah battery (a similar issue to one I’d discovered a few years earlier with another in-service CyberPower UPS below and to my right as I type this). I ended up finding one, labeled as being intended for a garage door opener (believe it or not):

but it wasn’t easy, and Amazon/CyberPower also don’t make replacement easy, either. There’s no user-accessible slot devoted to the battery; instead, you need to take the entire UPS apart, which is presumably intentional. When the battery dies a few years down the road, they’d prefer that you buy a brand-new UPS instead (with obvious environmental and landfill impacts).

Where else do I have UPSs begging for replacement? Well, long-term readers may recall that the furnace room beneath my office is the home network nexus. An ancient APC Back-UPS 650, the BK650MC, historically provided backup power for my QNAP TS-328 and TS-453Be NASs:

Yes, that’s a COM (serial port) for to-computer connectivity on the back panel, along with legacy POTS pass-through connectivity for surge protection purposes!

I honestly don’t know how long I’ve owned this thing, but it’s still chugging along (periodically fed by replacement backup batteries, of course). Reflective of its likely geriatric status, here’s a two-part review of it from the Ars Technica website archive, published in December 1999.

The other UPS historically in the furnace room, providing backup power for my cable modem, router and main switch, was a twin of the APC Back-UPS ES BE550G that had died last year:

Part of the motivation for (proactively, this time) replacing it—both of them, in fact—can be found in the last sentence of paragraph from which the earlier quote came:

That said, eventually the internal circuitry itself may fail, as seems to be the case with my device, with the UPS then destined only for dissection-then-discard.

More specifically, we’ve recently gone through a spate of brownouts and longer-duration blackouts here. I don’t know if anything specific is going on with Xcel Energy of late, or if it’s just coincidence, but given that my wife and I both work full-time from home, keeping the WAN and at least key portions of the LAN “up” as long as possible is a big deal. With the 550VA UPS, broadband would typically drop within around an hour. And I was also getting tired of rushing downstairs (inevitably in the middle of the night, awakened by a multi-UPS beeping chorus) to stably power off the NASs before backup power drained, potentially corrupting their multi-HDD RAID arrays as a result of the subsequent abrupt power loss.

I thought I’d hit pay dirt (and I actually did; keep reading) when I came across APC’s BX1500M 1500VA UPS:

APC sells the BX1500M for $219.99 on its website, although retailers such as Amazon typically list the UPS for around $184. And notably, Woot! recently had it for $149.99. Even better, the retailer was offering a few open box units for $124.87. And better still, a one-day 10%-off promotion further dropped the open-box price to $112.38. I grabbed the last two. When they arrived, one of them had something rattling around inside. Although it still seemed to work fine, I sent it back for full refund, among other reasons because as I later realized, I only needed one.

All was not perfect with the BX1500M, however, at least at first. Its replacement battery pack, the APCRBC124, sure looks proprietary (not to mention pricey), doesn’t it?

Not to worry, it turns out, as this video demonstrates:

Turns out the APCRBC124 is just two conventional 12V 9Ah SLA cells connected in series (24V result) by a three-wire and connector-inclusive plastic bracket, along with some tape to hold the whole thing together. I snagged the following photos from a bracket-only for-sale post on eBay:

The setup’s pretty slick, actually. You can insert the batteries-plus-harness assemblage upside-down (with the red-color sticker “up”), which doesn’t connect the battery pack to the UPS, for storage. Pull it out, flip it so the green-color sticker is “up”, put it back in and you’re good to go.

So why didn’t I end up needing two UPSs? Here are the BX1500M-displayed stats when both NASs, plus the networking gear, are all powered up:

86W of total power load, 9% of the total possible power supplied by the battery pack, which would only last a bit more than an hour on battery power alone.

Now, let’s shut down the NASs:

15W of total load. Only 1% of the total possible power supplied by the battery pack. And nearly four hours of estimated operating life on battery power alone.

Ok, so I still need to frantically run downstairs and stably power off the NASs each time premises power goes down, right? Nope. Turns out both NASs run QNAP-developed and -supported implementations of the Network UPS Tools (NUT) software suite. I’ve got the TS-453Be connected to the UPS via an APC-provided USB Type A-to-RJ50 cable and configured as the NUT server. Five (user-configurable) minutes after premises power goes down and the BX1500M switches to battery backup, it signals the TS-453Be to initiate a stable shutdown sequence. And the TS-453Be-as-NUT server then also then sends a command to the TS-231 NUT client, LAN-connected over the same (BX1500M battery-backed) GbE switch, to stably shut itself down, too (static IP assignments for both NASs are obviously necessary to ensure the desired outcome).

From then on, only the LAN equipment is pulling (much less than before) power from the UPS. Slick, huh? By the way, both QNAP NASs alternatively support something called “auto-protection” mode, which spins down and parks the HDDs and holds the NAS in standby while on battery power, auto-rebooting it when premises AC is restored. As QNAP’s documentation notes, this option is “recommended for business and enterprise users”…which doesn’t keep the NAS’s UI from recommending that I switch to it each time I log into the web browser-based UI. But it’s not necessary in my more modest setup, and I’ll take the extra battery life incurred by the full-shutdown alternative. Now I just need to set up similar USB-cabled schemes for the other UPS-backed computers in my stable, whose O/Ss either support UPS control natively or in conjunction with a UPS vendor-supplied utility…

Questions? Other thoughts? Let me know in the comments!

—Brian Dipert is the Editor-in-Chief of the Edge AI and Vision Alliance, and a Senior Analyst at BDTI and Editor-in-Chief of InsideDSP, the company’s online newsletter.

Related Content

• Putting an APC UPS out of its (and my) misery
• Standby and uninterruptible power supply tutorial – Part 1
• Optimize uninterruptible power in a non-traditional distributed way
• The Different Types of UPS Systems

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