Reading through the interesting comments in reply to your OP, I wondered what the UPS was intended for other than the router. I assume that for most it would be a desktop computer and monitor. There was also some mention of servers, but that's a special issue depending on how many and what their use is.
I don't have a great problem as I have a laptop - perhaps the simplest form of "UPS"! True, I'd require something else for the router, but what are others going to use their UPS for, and for how long is it intended to work in a domestic situation?
I have a UPS feeding the router, a dedicated firewayy microserver, and the ONT. As it happens, it also feeds the PBX (another microserver) and two more servers.
The desktop machines are on a separate UPS on the other side of the room. But there are four of those.
The OP's reference was to a "mini" UPS. These are different beasts from what most would recognise as a conventional UPS. They do not attempt to maintain a mains supply, don't have AC outputs and contain no inverter. A more accurate description would be a battery in a box with a charger. Designed to support one device with a low voltage DC input.
(Early adopters of FTTP broadband in the UK were often supplied with ONT "routers" that also included their own "UPS" of this sort - basically a box with 4xAA rechargeable cells, and a DC pass through. You plug the wall wart supply into the battery box, and the output of this into the ONT).
There is a certain amount logic to them - cheap and simple, and often able to provide long run times. They don't need costly inverters, and don't have to wast stored energy feeding the parasitic losses of the inverter, nor lose additional efficiency in the down conversion back to DC that the device's own PSU will then add.
That is in effect a fairly good approximation to a mini UPS.
Traditional UPS devices are usually sized to support a load for a shortish duration - long enough to ride out short power cuts, and also to signal computers to do an orderly shutdown when it looks like power is not going to arrive back any time soon. (posher ones also have a roll in mains conditioning and protecting hardware from the effects of poor quality supplies)
With many "integrated" UPSs you get the whole thing in one box including the battery. The battery will typically be sized to allow the UPS to run at full load for a short time. However at low load you may get over an hour of support. At full load it may only be 5 mins. So there is the option when choosing a UPS to over spec the load capability, so that you can run it at partial load for a longer time.
More pro oriented gear will use external battery enclosures, and a UPS will support multiple enclosures, so you can buy your total load capacity and run time independently.
Mine are all APC, I have 2x 2200VA and 1x 1400VA all saved from going into skips, only one of the 2200 presently has good batteries in it, it powers
FTTC router/wifi/4G backup dongle PoE switch (which in turn powers Hubitat zigbee home automation, raspberry Pi and mesh wifi extender) DECT/VoIP phone tower server (not always on) laptop/dock/monitor/audio interface/speakers
all that lot shows as below 20% load
the batteries are at 80% capacity these days (2 years old, previous set were dead after 5 years)
I've just run it for an hour, and that took the batteries down to 40%, in a real power cut I could shed some load by undocking laptop and turning off external monitor and speakers, should get me more than a couple of hours.
I might think about getting a pair of batteries in the 1400 so it can run the heating ...
Well, I have seen batteries that have a selection of outputs all available at once, and designed to run low voltage gear. I guess they include a charger. However with the myriad of plugs and sockets and polarities out there, I can imagine a lot of blown up equipment unless you are careful. All you need is a voltmeter that can tell polarity and measure the output from the psu. Often this part will have its output on it somewhere. In my case I'd have to get a laptop, and to keep the phone alive apsu for the truecall, and one for the router. Not sure that this is worth the effort, since chances are the next part of the chain at Virgin will go off as well, so maybe get a sum card and shove it in a phone with a hot spot? Brian
A 'mini UPS' for routers and such can be made simply with a car battery. Connect a regular battery charger to the battery, then also hang your various router/etc 12V loads off it. You would need to ensure that the charging capacity of the charger exceeds the loads taken by the router etc. If you want to get fancy you fit a low voltage cutoff for the loads.
(some of the £10 'solar charge controllers' have that feature: some can also MPPT track and know how to charge lead acid so you don't even need a car battery charger, just a 15V supply should be enough)
The loads would not be getting a regulated 12V, but most of them will be regulating down to whatever their internal supply rails are and don't mind that.
You can additionally run 'cigarette lighter' adapters off the battery: eg USB chargers and similar. They're a convenient form factor and designed to run off an unregulated 12V supply. You can also get car laptop chargers to plug in.
Main one I haven't solved yet is 48v PoE kit. I can use a passive PoE injector and a boost converter, but I haven't found a nicely packaged solution for that.
It's a shame that USB batteries (eg Micro-USB input of 5V from PSU, and USB-A output(s) of 5V from battery) can't (in my experience) be used as a short-term UPS for USB-powered equipment.
I tried it: my Anker battery cuts out the output when a plug is inserted to the input. So you only get an output when the input (charging) plug is manually removed. Grrrr. I'd use it as a cheaper UPS for the router if it didn't cut out.
60 seconds no-load power is impressive. If only the capacitor lasted a few seconds with typical load (motherboard, several spinning HDDs) a 1-second power interruption would be "invisible" when the substation switched to an alternative HV feed or the HV auto-recloser retried the original feed when there was a brief short to earth.
My wife's old PC came with an APC UPS (probably 700 VA). We never got round to trying it at the time, and when we tried it a year or so later (after it was out of warranty) we found that the battery would not provide 240V even with no load other than a high-resistance voltmeter. That was a waste of money. I suppose we could have tried to get a replacement battery to confirm whether it was the battery or the inverter that was at fault...
You should avoid the "lowest tier" of UPS products.
The boss bought the "lowest tier" UPS boxes for our cubicle computers at work, and the UPS boxes had a
10% defectivity rate (of a hundred units delivered). That means they're not testing them properly at the factory.
The defects were not all the same. A couple boxes would not switch to battery, when mains disappeared. More of the boxes, would switch to battery, then not switch back to mains, when the mains voltage reappeared. But, at least none of them smoked.
??? There are plenty of typically solar powered batteries that can be used to power and/or charge USB or iToys without mains power.
No idea if this one is any good or not, mine are older micro USB.
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I'd be willing bet the battery capacity is vastly over stated.
Typical standby power of 1W it works out at about 60J (Ws) stored energy. If the PC was running flat out at say 300W that translates to ~0.2s. My PC when idling or only doing light work runs at 60W so on a good day it might survive a 1s supply glitch without a UPS.
If you don't look after the deep discharge batteries properly then they will die if left uncharged for long periods of time.
Many of the power bank types can't run the load and charge at the same time. They only size the input converter enough to charge, and some of them won't charge if there's a load connected - they may have a single converter that's used to both charge the lithium cell or drive the output, but not at the same time.
The solar ones may be better (they obviously need another converter for the solar panel), but no guarantees they can charge from USB while at the same time outputting.
Interesting point you make. Thanks for the pointer.
I will experiment when I have time to see if that is the case. If that is the case then my interim solution would be a pass through Schottky diode logical or of the incoming USB supply and the battery pointing at the load and hope that when the input voltage drops to zero the battery will take over supply.
It hadn't occurred to me that they would be so badly designed as not to accept charge whilst delivering output. I will experiment with the ones that I have during the almost inevitable power cuts this winter. eg.
(only positive side of circuit shown 0V is all common)
SO long as the PSU is on the Load takes power directly from it and the battery can charge from whatever is left. PSU fails then the diode from the battery conducts and it takes over. I guessing low voltage drop diode will be OK otherwise it will have to be a change over relay that is held closed by the PSU being active and drops to battery if not.
I'm about to get some bare USB sockets for another project (a small USB powered amplifier to match the TV volume to that of all other sources).
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