Figuring out current draw

So I'm working on a project with an unknown and not sure how to figure out what I need to know. My customer wants new USB chargers and I'm trying to figure out if the circuit will handle the load of the new chargers. The current charger is a single USB A. Input is 28VDC, output is 5VDC at 3 AMPS, 15 WATTS. Not sure what formula to use to compute current draw on the input side. My new chargers consume 1.25AMPS each.

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kmikemoo 27 days ago +1

There really isn't a formula that is going to give you the answer that you seek. " P = (E * I) + losses " isn't much help. If you measure your input current draw, you can figure out what those losses are…
michaelkellett 26 days ago in reply to dang74 +1

And you need to take account of switch on surges - it's often very hard to get good information from suppliers.. In cases like this you need to choose the closest replacement you can find and do some…
michaelkellett 21 days ago in reply to inavitech +1

If this is on a plane won't it need the full certification stuff ? MK

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inavitech 22 days ago

That's the thing, just can't find any formulas to do the computations. Guess I'm going to have to wait until the aircraft comes in and pull one of the outlets they want to replace and see if the data plate has any good information to help determine what the circuit is drawing off the branch and go from there.
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michaelkellett 21 days ago in reply to inavitech

If this is on a plane won't it need the full certification stuff ?

MK
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michaelkellett 21 days ago in reply to inavitech

If this is on a plane won't it need the full certification stuff ?

MK
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