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Comment by davidhyde | Hacker News Reader

I think that what the author is really looking for is a battery inverter setup and this is quite a mature market. A lot of countries out there do not have stable electricity supply and these things work for all appliances. Something like this (https://bluettipower.co.uk/products/bluetti-ac500-b300s-home...) although there are a huge range of brands and prices in this space.

Pc UPS’s are underpowered and the market is so swamped with cheap garbage as the rant suggests that it is difficult to find anything decent.

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I mentioned this below in a reply to a similar suggestion - It is critical to remember that most of the 'battery house backup solutions' do not have fast enough switch time to switch without rebooting some computers.

Most of the battery systems (like EcoFlow, Bluetti) has switching times that are between 30 and 100ms. The larger Enphase ones are ~100ms, and the Tesla battery system is around 25ms.

Online conversion UPSs have 0ms, and switching ones are usually in the 4-8ms range. Some systems can handle 30ms, most can't handle 100ms.

I wonder if there is a market for flicker preventer which stops devices from restsrting on quick drops. I have more things that don’t want rebooting than ones need to keep running.

I don’t know if could use capacitor or need battery. If need lots of battery for load, might end up with UPS. It would need to be cheap.

Well, a flicker preventer is a double on-line UPS, so the market has a device, albeit an expensive one. You could purchase a double on-line UPS that has small batteries and that would serve as a 'flicker preventer' while providing only a small bit of runtime.

It would be possible to build this kind of on-line conversion with a very very small battery that could only provide power for a few seconds, and that kind of device would serve the goal you mentioned. I suspect the cost for this device would quickly approach a UPS in cost, so it might not be the 'cheap' solution.

There is a market, and it has players.

One way is small, inexpensive standby UPS: Something with fast switchover, but without the capacity to survive anything longer than necessary to avoid some flickering and to conduct an orderly shutdown if the badness persists. This is the cheapest way. (And for small low-voltage loads like Raspberry Pis or consumer routers, there are kits available using things like 18650 cells.)

Another way is a small-ish online UPS. These have no switchover time, but they're more expensive because the parts are bigger, and they're less efficient than a standby UPS.

Another way is a ferroresonant transformer. This isn't cheap, but it is lasting (no moving parts or chemistry to degrade) and can work through some flickering.

And finally: Motor-generators, with a flywheel to pick up the slack. These work fine, but they're big, alarmingly expensive, require maintenance sometimes, and there are good reasons to be scared of spinning flywheels.

That is a lot more expensive than a UPS!

I did use PC UPSs quite successfully in the country with frequent power cuts.

On the other hand I do take the point that the inverter would not fail loudly as one of my UPSs did when my ex-wife decided to plug a hairdryer into it.

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