Some people seem to be of the opinion that a pure sine wave inverter is somehow better for charging laptop batteries than non-sine wave inverters. That seems wrong to me; I can't imagine why the THD of AC going into a digital power supply that puts out low voltage DC to charge a battery matters to the laptop that is running from the battery. Am I missing something? Thanks.

 

It depends upon how the laptop power supply converts the AC to DC.
The peak voltage of a pure sinewave is higher than the peak voltage of a square-wave or quasi-sinewave for the same RMS voltage, so if the adapter rectifies the AC to get the peak voltage, the resulting DC rectified voltage could be too low for proper charging with the non-sinewave input.

 

Some people seem to be of the opinion that a pure sine wave inverter is somehow better for charging laptop batteries than non-sine wave inverters. That seems wrong to me; I can't imagine why the THD of AC going into a digital power supply that puts out low voltage DC to charge a battery matters to the laptop that is running from the battery. Am I missing something? Thanks.

Theres no correlation.

I have never seen a laptop power brick that wasn't SMPS which pretty much guarantees that no matter what the AC input source voltage frequency and waveform shape is, if it's within its intended design limits (+- 10% on most) it doesn't really matter being whatever it is gets turned into DC voltage then stepped down to eventually come out a clean stable DC power.

Then past that is a second SMPS system of one variant of another inside the laptop that handles all of its various system voltages plus battery charging and discharging work effectively making a second firewall of input power filtering and regulation plus does the actual battery charging management.

Or at least that how pretty much every modern and even marginal quality laptop made works.

As far as a common laptop power brick is concerned if you give it a DC voltage within the range of input voltage it's rated to work at it will work just fine too!

 

It depends upon how the laptop power supply converts the AC to DC.
The peak voltage of a pure sinewave is higher than the peak voltage of a square-wave or quasi-sinewave for the same RMS voltage, so if the adapter rectifies the AC to get the peak voltage, the resulting DC rectified voltage could be too low for proper charging with the non-sinewave input.

Thanks. What would the effect be on the battery?

 

Thanks. What would the effect be on the battery?

I believe tt is correct.
The input waveshape should have no effect on the battery.