Why do UPS have such tiny batteries?

What is your UPS supposed to do ?

Given most outages are surprise and can take an unknown time t recover, I'd suggest their key role is to allow the system(s) to perform a clean shutdown. Whether this is quite as necessary in the days of SSDs, I can't say. Personally I'd prefer all running processes to close files etc etc.

My grumble with UPS is when I had one (home rig) I ended up having to replace the (burst) batteries twice with nary a brownout.

Of course within weeks of deciding to abandon it, we had a power cut.

Many UPSes are designed for a smooth shutdown of systems, rather than keeping them going for hours. They can handle small dropouts of the supply but aren't intended for where the grid might go away for long periods. Off-grid battery systems (eg Victron) are more intended for the latter situation.

It's possible to buy UPS-style DIN-rail lead acid battery chargers/managers from eg MeanWell (sold at Farnell/CPC):

Theo

After some more searching I think I have found what I want, they're sold as inverters "with UPS function". Basically they are a complete UPS without a battery. I now have to navgate the eBay/AliExpress/Amazon maze of exaggerated claims to actually decide what to buy! :-)

My APC SU2200 has 4x 12V @ 19Ah (a minor upgrade from the 17Ah batteries it was supplied with)

If the main PC is asleep, it'll run the router/switch/WiFi/VoIP/DECT/home-automation for hours ...

IMHO the place to look is motor home supplies. It is quite common now to provide continuous 240V via an inverter from one or more leisure batteries which are in turn charged via a mixture of solar, 240V mains, and the alternator on the MH.

There are some inverters which will kick in automatically when mains power is lost.

Cheers

Dave R

Ive never had UPS. All my *nix machines generally survive a power crash OK

The only really bad instance I ever had was a machine self-rebooting just as the power went out again,. It never recovered from that. These days they don't self reboot, mostly.

Many will be sized to support systems long enough for a safe shutdown when at full load. The limitation of batteries are they are often big and expensive - so they often go for a small as they can get away with.

If not running at full load then you will get longer run times. My 1kVA UPS (2 x 12Ah SLAs) will run a PC and screen for 30 to 40 mins if it is not working too hard.

Yup, some commercial UPS systems are designed to have as many external packs as you need - but a for a price!

You could also look a the various portable power back devices that use LiIon batts and can charge from multiple sources. (Bluetti, Jackery, Ecoflow etc)

In the 6 years we've lived in our present house, we've had numerous power cuts that have lasted a couple of seconds, due to HV feed to our substation tripping and reconnecting (or an alternative HV feed kicking in). It seems to be overhanging branches or cattle using wooden HV electricity poles as scratching posts. And yes, we have played merry hell with Northern Powergrid when it was happening every few minutes for hours on end. A 1-second break is as bad as one lasting 10 minutes, an hour or six hours: we still need to go round and power-on all our mesh network nodes in sequence: if the all start simultaneously when the powere is restored, at least one of them will fail to connect. (*)

Long power cuts have been rare. A few weeks ago we had one of about 6 hours which was pre-planned (replacement of HV transformer in substation), and one of a few hours following a brown-out down to 96 V (failure of one of the HV phases). (We were prepared for the 6-hour power cut: we'd charged USB batteries to top up phones and laptops once their internal batteries were starting to run low, and we bought a battery air pump for our fish tank: they managed OK with no filter pump or water heater. The break was 10 AM to 4 PM, so we managed without room lights, and my Kindle has a back light so I could read even when the room got a bit dark. We have a gas Aga and a wood-burning stove which provided heat for that part of the house while the boiler was off.)

The problem with UPSes is that you need so many, depending on whereabouts in the house the equipment is located that needs uninterrupted power. We could use one to power the router, the primary mesh-network node and a few important things like DECT phone base station (although I have a wired phone which I can plug in during a power cut). But then we'd need four more of them to power the other mesh-network nodes, otherwise we wouldn't have internet at the other end of the house where my wife works.

When my wife bought a PC many years ago, she bought a 700 VA UPS because it was offered at a discounted price as part of the bundle. By the time we tried the UPS, its battery was utterly useless: it would run a 60 W tungsten light bulb for about 2 seconds (**) before cutting out if we pulled its mains input. By the time we discovered this, the warranty had expired. Moral: if you buy something, test it immediately and a frequent intervals.

(*) Bloody stupid mesh-network nodes. They use 5 GHz wifi to communicate between nodes to daisy-chain back to the parent node, which has a relatively small range that governs how far apart the nodes need to be. But... if you want 2.4 GHz wifi as well (some devices don't speak 5 GHz) then the nodes are so close together that they overlap, which means the auto-channel algorithm struggles to negotiate the best choice of non-overlapping channels - eg 1, 6, 11 - when the all turn on simultaneously. It would be nice if you could turn on 2.4 GHz for just the nodes that are in range of the non-5 GHz devices, reducing node-to-node contention for channels.

(**) Even a neon "candle flicker" bulb, which uses < 1 W, only lasted about 5 seconds.

I used to use a Windows PC as a video recorder (until I replaced that functionality with a Raspberry Pi) so that PC needed to be on 24/7 (bloody wasteful of power!) and I set the BIOS to restart the PC if the power came back on after a power cut. Once we went through a phase of

The RasPi has been bulletproof in the 4 years I've used it, enduring multiple power cuts and being back in service within a minute or so of the power coming back, without the external spinning HDD (NTFS filesystem) needing to be repaired.

It's a shame that USB power packs aren't usually capable of charging and supplying power at the same time. I thought about using mine, connected to a mains PSU, to power USB devices - normally passing through the power from the mains to the device, but continuing to supply 5 V off the battery if the mains fails.

Sadly all of ours cut off the output as soon as the input (from a mains PSU) is plugged in.

A while back I bought a cheap powerbank/jump starter for my car. I’ve just been a fetched it out of the car and it does indeed seem to work as a UPS, simultaneously charging from a standard USB C lead whilst supplying power out on its USB A sockets.

Deal: GREPRO Jump Starter Power Pack, Car Battery Booster Jump Starter and Jump Pack (up to 6.5L Gas, 4.0L Diesel) for 12V Vehicles, Motorcycle, Battery Booster with LCD Screen and LED Flashlight

Tim

APC do a series of rack mount UPS, Theres a 5kW version, a 8 kW version and a 10 kW version and all 3 models allow you to hook up a further 10 UPS batteries.

The battery pack connecting leads are at 192V DC as well. Obviously adding on the extra battery packs increases the run time.

BTDTGTTS

It's less of a worry with SSDs, but can hammer spinning rust.

There is an "In the event of power failure" setting in every Bios, that I've come across, for that.

I'm not in to caravan/camping but I've found lots of interesting info on ExploreVan -

Beware of setting it to "power on after failure" - it can be problematic if you have a power cut/restore/cut/restore over a minute (which I have).

Not sure it exists in Raspberry PIs... I must check...they don't have 'on off' switches.

A while ago when my wife had an illness and the doctor advised that she must be kept warm, it was approaching winter so I needed to keep the central heating operational. I already had a spare car battery in good condition and kept that way by an intelligent charger that kept it 99% charged without overcharging it. I also know that my gas central heating boiler and pump don't take much power, but without electricity the gadget that releases the gas won't work. So I bought an inverter to make 230V AC out of a 12V input, so that even if we had to sit in the dark, the radiators would be on. It tested OK as a solution to no mains, though I haven't needed to use it in anger since then.

Recently, my Virginmedia phone got converted from wired to VOIP, so if I want a landline phone to work in a power cut I will need the router to be powered. There should be enough output from the inverter to concurrently power the router (via my wind-up extension lead; the boiler and the router are in different rooms) but I haven't tested that, and in any case I have a mobile phone.

Some years before, I invested in a UPS for my desktop. The one I bought was supposed to switch over automatically to battery in the event of a power cut, run the PC until the batteries inside were running low, then tell the PC to shut down tidily. When the mains was on it still ran the PC from the internal batteries, but concurrently it kept the batteries fully charged.

The good news is that when the power went off one day it kept the PC (and router) running exactly as I expected. The bad news is that when the power came back on, it did so with a nasty voltage spike and that did the UPS electronics no favours. The logic that when the mains power was back it should recharge the internal batteries got fried. I only found this out when the mains was back on (the house lights were working) but the PC still shut itself down a bit later when the UPS battery life ran low. I had to take the UPS out of the input arrangement to get the PC to boot.

Perhaps in these unreliable energy times we will in the end simply power our homes off batteries completely, topping them up when the mains is actually on...