If I have for example a battery that outputs 10 V but with a maximum of 0.5 A. If I took the output of the battery and entered it in a buck converter to get 5 V will I get the same 0.5 A at 5 V or I will get 1 A?

In my small knowledge what I know that the watts should be the same so 10V * 0.5A = 5W, so 5V * 1A = 5W. Is this true or it's only theoritical?

  • \$\begingroup\$ A battery voltage usually varies some over its active life. For example, a LiPo might start with \$4.2\:\text{V}\$ but end with \$3.7\:\text{V}\$ when it needs to be recharged, again. Also the current "maximum" is a "compliance" value. This doesn't mean you have to always use that much. It just means you can get up to that range and stay within the voltage range specifications, consistent with the remaining available energy. A buck converter will need to operate well over the source range of the battery and the current required from the battery will vary as the battery voltage changes. \$\endgroup\$
    – jonk
    Oct 13, 2019 at 7:56
  • \$\begingroup\$ have you tinkered with bipolars and resistors and LEDs, to turn the LEDs on and off? have you built any bipolar amplifiers? \$\endgroup\$ Oct 13, 2019 at 21:25
  • \$\begingroup\$ @analogsystemsrf nope, I didn't do this before, tell me more please \$\endgroup\$ Oct 14, 2019 at 4:48

1 Answer 1


Assuming a buck converter that's 100% efficient, yes, you will be able to draw 1A from the output.

In practice, buck converters can be very efficient, often over 90%, so you'll still be able to get around 900mA output, which is rather better than the 500mA you'd get with a linear regulator.

An important part of the buck converter system is its input filter capacitor, which provides pulses of the high output current to the converter, while drawing the continuous average lower current from the input.

  • \$\begingroup\$ Theses things can also be applied to solar panels also right ? \$\endgroup\$ Oct 13, 2019 at 13:01
  • 1
    \$\begingroup\$ @ShamsEl-Deen Certainly. Solar panels can have quite a wide output voltage range, so make sure your converter's input is specified to cover the whole range, not just the nominal panel voltage. \$\endgroup\$
    – Neil_UK
    Oct 13, 2019 at 13:22

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