<p>So apparently the wiring in my home is... questionable. Very rarely, plugging or unplugging things will cause a power dip. This is almost always the result of turning on a fan or something, is only for a moment before coming back, but its long enough to cause my printer to reset. I want to add a backup battery supply using either the 12v cell pulled out of an old apc ups (before the suggestion of just plugging it into that... I did, somethings fried in it and it will ALSO power cycle everything connected to it every few hours) or an old car battery. Is there any reason I shouldn't use this circuit, which was originally intended for amateur radio equipment? <a href="https://i.stack.imgur.com/Jd7Sp.gif" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/Jd7Sp.gif" alt="battery backup circuit"></a></p>

<p>Also is there anything else i should be considering?</p>

[{'answer_id': 6718, 'author': 'profesor79', 'author_id': 9730, 'author_profile': 'https://3dprinting.stackexchange.com/users/9730', 'pm_score': 2, 'selected': False, 'text': '<p>This circuit is correct as it does the job (provides a charge and switch-over when needed). </p>\n\n<p>The only drawback could be that you need to ensure that the battery is sealed as during the charging process the electlorit will slowly evaporate and decrease battery capacity.</p>\n\n<p>I am personally using a UPC as that gives me more options to power-up more stuff including 240V heater and it has a self-test built-in (it is APC1500VA).</p>\n'}, {'answer_id': 6720, 'author': 'Sean Houlihane', 'author_id': 4927, 'author_profile': 'https://3dprinting.stackexchange.com/users/4927', 'pm_score': 3, 'selected': True, 'text': "<p>There are a couple of points to consider with this question. First, you will need to make sure the PSU is correctly adjusted to the float charge voltage of the 12V battery. SLA should be safe to float charge, but over voltage will damage it over time.</p>\n\n<p>One alternative solution (since powering the heaters will limit your run time) is to detect power failure, cut the heaters immediately, and save state to EEPROM in the firmware. This is the approach taken in the latest Prusa printers, and is a bit more complex, but might turn out to be more reliable.</p>\n\n<p>If the problem you are solving really is brown-outs, then a simpler solution might be to isolate the high current and control sides of the circuit. The MCU will be run from a regulated 5V or 3V3, so a large capacitor (with diode isolation) on that regulator's input would do the trick.</p>\n"}]
['https://3dprinting.stackexchange.com/questions/6715', 'https://3dprinting.stackexchange.com', 'https://3dprinting.stackexchange.com/users/12706/']