I suggest getting information from an owner of a 5V input (USB) battery charger, regarding the amount of TIME to charge a battery compared to using 110V US /240V Int'l voltage input.
The output rating from a Sterlinktek that I have for LCE6 (7DII) battery is 500mAh, compared to 1200 mAh from a Canon charger...only 41% of the charge rate!
The output rating from a CTA that I have for BP511 (40D) battery is 700mAh, compared to 1200 mAh from a Canon charger...only 58% of the charge rate
I bought my chargers simply to be able to charge while driving about, if not near an AC power source for a number of days. Rate of charge was not of primary importance to me. OTOH it sounds as if you want/need to recharge while 'on the job' and have depleted batteries that you need to replenish on the spot rather than back in your room that evening, so charge rate would be important.