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I have a network device that runs on a power supply rated at 48v about 1.2a. it plugs into a 120v diy ups (a power switcher from an rv with a battery and an inverter). This seems to work fine on other devices but with this particular device when the power switches to the inverter, the device resets.

I'm thinking the power dips just a little too long and I might be able to put a capacitor either inline with the 48v cable or maybe by opening the power adaptor and replacing their capacitor with a bigger one.

Are either of these feasible and how do I know whether it will solve the problem?

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Yes you can use a capacitor to cover power outages .It may not be practical for you .Remember that 1 Farad is 1 coloumb per volt ,this means 1 amp for one second for a voltage drop of 1 volt .If your power dip is not for too long like 100mS and your 48V 1.2 Amp load can tolerate 8volts droop then .o15 Farad will do it roughly .You could paralell 3 4700uF 63VDC electrolytic caps which is not expensive or exotic .If you need much more backup then lots of Supercaps or Ultracaps in series will work if they are voltage balanced .

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  • \$\begingroup\$ Why 63VDC? Will it ever release that much? Or will it only ever get to 48V because the parallel charge is only 48V? and yes, I likely only need it for about 100ms, but I'm not sure how much voltage drop I can handle. \$\endgroup\$
    – DAB
    Oct 1, 2020 at 18:15
  • \$\begingroup\$ If it helps, the device is a network switch that provides PoE - when I switch power sources, the PoE light row appears to stay on consistently, but the data connection row turns off and takes a second to come back on. Meanwhile, the modem shows no impact at all, but it also has a much lower draw. So it might even be a voltage dip because the inverter is warming up to the load. \$\endgroup\$
    – DAB
    Oct 1, 2020 at 18:17
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    \$\begingroup\$ @DAB .63VDC rating is not compulsory .It gives a sensible safety factor on a regulated 48VDC supply .A 50VDC cap would not .A 100VDC cap would be great but would be larger and cost more money. \$\endgroup\$
    – Autistic
    Oct 5, 2020 at 20:24

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