Yes, that will work (it's a switch mode step down converter as I suggested in my first post) but be aware the 3A out is the absolute max current (and probably isn't to happy to run @ 2A+ for long). So if you set the charger to charge to fast it will fry the converter.
Link to your LM2596 module?
What kind of battery were you charging?
So set the step down to 18V and indeed cool the step down. Also don't charge faster then 2,2A or more then 3 LiPo cells with this setup because the step down is just to light for that.
Of course you have to waste all the power, whereas using the right power supply in the firstplace would avoid that.
is there any other kind of diode that i can drop it more but with a single diode not more ?
QuoteYou already have your input voltage (19V). All you need is the regulator circuit.
You already have your input voltage (19V). All you need is the regulator circuit.