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I have following UPS: https://www.cyberpowersystems.com/product/ups/pfc-sinewave/cp1500pfclcd/

  • It has max power of 1000W
  • It uses 12V battery

at 12V it has to draw 83.33 amps in order to output specified 1000W. This is the battery: https://www.cyberpowersystems.com/product/ups/replacement-batteries/rb1290x2/ . Does it look like it can possibly support such current?

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  • \$\begingroup\$ Not for long. And indeed the UPS "product details confirms this : "Runtime(half/full) 10/2.5 minutes." Yes, each of the 2 batteries can probably supply 40A for 2.5 minutes. \$\endgroup\$
    – user16324
    Oct 4, 2020 at 21:06

2 Answers 2

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It's the battery the manufacture specifies for that UPS, and CyberPower is a reputable brand. I expect it'll work just fine - as long as you keep its specifications in mind.

The UPS itself is rated for 2.5 minutes of run time at full load. That is, it will run for 2.5 minutes while delivering 1000 watts.

That's a 9Ah battery. Just on the mathematics, that's about six minutes at 83 amperes. Throw in losses (conversion to AC and from heating in the battery during discharge,) and that 2.5 minutes sounds about right.

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The AH (Ampere-hour) capacity of a battery is specified at a specific rate of discharge which is typically 10-hour or 20-hour rate. Thus a 9 AH battery capacity specified at a discharge rate of 10 hours means that it can supply a constant current of 0.9 Amp.for 10 hours before it gets fully discharged. As the discharge rate is increased its AH capacity gets reduced. If the discharge rate is abnormally increased its AH capacity will also get reduced drastically. Thus a 9AH battery at a discharge rate of 83 amp if it lasts for 2.5 minutes we are getting a capacity of around 3.45 AH, assuming 10% losses in conversion from 12V DC to 120V Ac, the 9 AH battery is delivering a capacity of around 3.8 AH which is quite reasonable. If a single 9AH battery is used in UPS, it can be safely assumed that it has been designed to deliver 83 amps for a short duration.

Depending on the number and size of plates in a cell (which decides the AH capacity of battery), lead-acid batteries can support even much higher currents say hundreds or thousands of amperes as in the case of telephone exchanges.

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