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For example, let's say I have a 10 amp circuit. Under normal load the hardware only draws 6 amps. However, it is possible that the hardware could draw up to 11 amps (for instance during boot). Is there a UPS like device that provides a 15 amp circuit and draws from a 10 amp circuit? This device would use a battery to cover the 5 extra amps during those short periods when the hardware is under heavy load.

I know in the datacenter the best option is to go with a redundant circuit, was just curious if something like this existed and if it's even feasible.

Patrick Lorio
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  • This is feasible although I've not seen ups's that do it. I postulate 2 ways it could be implemented - through a current limiting circuit connected to an online UPS or by connecting a charging circuit to a battery and the battery to an inverter. – davidgo Nov 22 '19 at 06:43
  • Interesting. So basically get a UPS rated for a higher circuit then limit the source. I'm not familiar with current limiting circuit. Does it basically just drop the voltage when the draw is too high rather than breaking the circuit? – Patrick Lorio Nov 22 '19 at 06:55
  • Its been 25+ years since I did electrical engineering course, but I'm pretty sure the current is clamped. Limiting the voltage won't necessarily help due to "buck and boost" features if UPS's to compensate by drawing more current at lower voltage and then correcting. – davidgo Nov 22 '19 at 07:02

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Yeah, it is called a UPS.

Get a UPS that is rated for 15 amps output and has a configurable input load (i.e. uses only 10 amps to load the battery). IT will then load within your limit and fall back to the battery when using more. I have that here in place and it works like a charm.

THAT SAID: obviously you should use 20 and 15 as measurements here because you always use max 80% of the amps in every step ;) Just using your numbers as example.

TomTom
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  • Thanks! I was originally going to ask how this could be done with a UPS, after quite a bit of googling I couldn't find anything. Is the configurable input load a common feature? What search terms should I use to find a product with that feature? Thanks again. – Patrick Lorio Nov 22 '19 at 06:51
  • Common is relative. It IS common - on higher end UPS and very high load UPS. Mine takes 3 phase input and can use up to IIRC 64 amperes on each line. Once you go on that level, some sort of input load management may be mandatory. This definitely is a RTFM thing - you need to choose some good UPS and then read the manual for input load management. – TomTom Nov 22 '19 at 06:53