Need Clarification on AC to DC Conversion Calculations
I work a lot with electricity including conversion, in mains AC power, electric drives, off-grid/solar, electronics and automotive. 

I know a joule is a watt-second (making joules-per-second, a Star Trek unit, quite amusing.)   It took some detective work to figure out what a coulomb is.  



Turns out, it's not a Space Shuttle.   

The number of electrons in an amp is not a particularly useful number, partly because none of the electrons in the mains power actually go into the battery. Generally they whirl around a transformer core, which induces other electrons in another winding to get happy feet.  9-20 times as many, due to the magic of electromagnetism, though with a fraction of the verve.  Ultimately it ends up being not worth thinking about.    

So no, number of electrons is definitely not preserved. 

Watts and joules, pretty close, that dance is rather efficient. Thank you Mr. Tesla.