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Is it possible to simply add a car/truck battery to my computer's PSU output, in parallel, to make sure if there is a power outage, that the computer will seamlessly continue running, for a period of time (just like an UPS unit would do, but it's more advanced, of course)?

What is the best way to do it, in terms of battery life? I'd like to do this as a DIY project, to learn more about this topic and to create something useful out of it.

I understand the UPS units exist for a reason, but I'm also curious is it possible to do it in a more simple way, like stated above.

Thanks in advance for all the answers!

Mladen B.
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    Here ya go brother: https://electronics.stackexchange.com/questions/525213/using-two-diodes-as-a-simple-power-supply-backup-switch – Kyle B Nov 13 '20 at 18:40
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    Are you going to implement the charger, notifications, graceful shutdown and all other functions of a standard UPS? No? Get a UPS. – Lior Bilia Nov 13 '20 at 18:40
  • The only realistic ways to do this are either to buy a power supply with this feature, or use an inverter type UPS to feed the battery to the existing power supply. – Chris Stratton Nov 13 '20 at 18:45
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    you could try a PSU that's fed DC instead of AC, often used for mini ITX designs, and put your batteries before it and after the wall wart. They usually take 18V, so you need 3 6v batteries in series. – dandavis Nov 13 '20 at 20:59

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A car battery is a single 12V source. But your computer's MoBo requires 12V, -12V, 5V, and 3.3V. So it's not possible to connect a backup car battery directly parallel to a PC PSU's 12V output.

Also, a car battery needs ~14VDC for being charged. So a PC PSU's 12V output cannot charge the battery.

Rohat Kılıç
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No, not really practical. That's because computers do not only run on 12V. The power supply outputs multiple voltages. Even if it did only run on 12V, the battery voltage would also fluctuate too much depending on the state of charge. The circuitry to charge batteries and then providing a standard set of voltages needed for a computer would be more complex and expensive than simply getting an UPS.

Justme
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  • But there no any project to make it's real? Only for electric hack's knowledgment. I guess, feed a desktop computer only with batery like laptops today is, will save more watts one time no waste transfom 12V DC batery to 110V or 220V AC to again +12V, -12V, +5V, -5V, 3,3V and etc.. – Alexsandro Nov 24 '22 at 02:14
  • @Alexsandro You seem to be talking about a differrent scenario. Computer power supplies that take in 12V (or 24V or 48V) do exist and can be bought. But you can't just simply put a battery between a regular power supply and motherboard. If you do, you still need all the complexity of charging the battery and switchover between original supply/battery and generating the necessary voltages. If you need that, it does not exist unless you buy a laptop which already does it for you, and even for the built-in display. – Justme Nov 24 '22 at 05:34