I am working on a design project where we are being asked under EN 62368, to classify the maximum power the battery can output.

In the standard, under clause, the standard specifies that you are to take the power source (say a battery), disconnect the "load" in the circuit, insert a variable resistor, and put in a watt meter to measure the power as so you increase the resistance of the variable resistor.

Depending on the wattage drawn by the variable resistor in your circuit, you then classify the power source and applicable rules apply.

Is there a way you could estimate from a LiPo or alkaline cell datasheet what the theoretical maximum discharge would be?

Like I hand you a 1.5V AAA battery, is it known what the maximum power (or close to it) that could be drawn from the battery is by some property short of having to wire up an adjustable resistor and empirically measure?

  • \$\begingroup\$ Datasheet will show the maximum discharge current. You already know the voltage... \$\endgroup\$
    – user16324
    Commented Jul 29, 2021 at 15:52

1 Answer 1


MPT theorem states the condition is to match the source resistance, which is a condition that cuts the voltage in half. but this would be equally dissipated in the battery so , there must be a voltage limit to be reasonable or a fuse.

Otherwise with 3.8V and 50 mohms ESR and 50 mohm load , you get 38 A.and over 100W for a short pulse.

  • \$\begingroup\$ The standard makers of EN 62368, curiously have not considered MPT.... ;) -- this is why they want to remove the "load" from your circuit and plug in a variable resistor, that way any resistive elements to the product are accounted for and you just plug and play with a wattmeter. So to your point, perhaps there is a point to measuring this on your board. \$\endgroup\$
    – Leroy105
    Commented Jul 29, 2021 at 2:38
  • \$\begingroup\$ I could not find this ref. to battery power max, but the new -2 std. is to increase safety, so that means you need a fuse or polyfuse to limit power to some xx Watts \$\endgroup\$ Commented Jul 29, 2021 at 13:17

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