I know the 901 manuals have to use an extender to charge in the orig chargers.
I think I recall an adapter for the 510 also back a few months ago when I started
vaping. I am sure a
mod site would have them... or something that would work.
Why are you using a USB charger? I read about 3-4 hours to charge on a USB, maybe more on a mega. My 510 batts charge in like 1.5-2 hours MAX
Use an AC charger for now?