I would say look for an "on-line" UPS that corrects the voltage supplied as needed. This allows you to survive a brownout much better. APC are always good!
Sorry I wasn't clear in my first post. Was meaning have your usual mains UPS for the server. And a 12V one for the other devices. Because you only want to be able to gracefully shutdown the server. Yet need more run time for the other devices. Also the circuitry in a typical UPS will be quite lossy. so the runtime Vs load curve definitely won't be linear. (often the batteries are just 7Ah 12V ones anyway)
My system is very simple - Power supply feeds batteries, Batteries feed devices. I had a look at the open UPS kits. Sure they offer smart charging of the batteries. Which means you could use Lithium ion if you want. But they don't regulate the output. Meaning you are still stuck with a supply that has some variance to it.
Check the specks of your Mikrotik. It may have an input voltage range instead of a fixed voltage. (My Edge router lite can handle input voltage from 9 to 24VDC) The Mikrotik might be the same.
Also DC - DC switchmode supplies are stupidly cheap on Aliexpress. So getting 24V from 12V is no problem. And efficiently getting 5V is no problem either. Only you would want to add over voltage protection yourself to the outputs of those supplies. Easy to do - just get an SCR and a zener diode. (google SCR crowbar)
And a big advantage of a 12V UPS system - You can power it from your car. Which means you can keep it going in an extended power cut. Even if you don't own a generator.
The voip device may need an isolated power supply to work properly. I have not seen cheap isolated DC-DC convertors anywhere yet. I would like to get some for some audio things I have that wont work with a common 0V connection between them.
Yep - good spot - the Mikrotik is listed as supporting an input voltage between 8-30V.
Do you not have any device between your DC input and your battery - it is just a direct connection? I don't know much about batteries, but do you not need to perform some sort of trickle charging? And limit/shutoff once the battery is charged? I think building custom SCR Crowbars (I did google it and understand the concept) is probably a bit beyond my skill levels at present - and I have a 100 other jobs to do as well!
I am starting to think a simple UPS which just gracefully shuts down my server, giving it time to send out a notification that there has been a power failure (via cloud based notification services like Pushover/SMTP/Twitter etc) will be sufficient. During the ChCh quakes pretty much all comms was over cellular - and we could charge our phones in the our cars. The authorities managed to wheel out generators to most of the cell towers in pretty quick time.
Still interested to know of anyone that has a view on how the Eaton Evolution 1550VA compares to the new Eaton 5P 850VA? Since they are available for the same price currently...
I cant help with the Eaton question but just for reference I have an APC ES 700G on a 4 drive QNAP NAS, Zyxel router, 24port switch, SPA112 and a couple of misc devices. My NAS is set to shutdown after 10minutes (so it stays up if I accidentally trip a fuse or something) and with all devices connected the NAS reports the running time of the UPS as just over an hour. With the NAS shutdown I'd expect everything else to stay up much longer.
So I am a bit torn - I can get a cheap Dynamix 1200VA for $180 or go for the APC/Eaton 850VA for around $600. Big price difference, and obviously a big jump in quality. Just wondering if the extra money is worth it when all I really want is to get a notification in case I am away from home that power was lost, and to shut down my Ubuntu server gracefully.
I know the experts will say steer clear of Dynamix, you get what you pay for etc. But I can buy 3 Dynamix models for the price of one APC/Eaton so is it more cost effective to buy the cheaper model and replace every couple of years?
we use the 500w ones at work, and they are ok for powering a PC (power is very dirty at work as its diesel generators on a ship) but they didnt last that long, as they are always switching to battery. cant comment on them in a home environment, though i have a couple of them here ive never used them
Yep - they do have a USB interface, and some Dynamix software called NetGuard. I am hoping I can get the more generic NUT utility to work on Linux however. They do seem very cheap...
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