I have a friend who is completely enamored with my slim chargers. He's got a 650mah VV ego with a 808 adapter, and wants to know if it's safe to use it on a slim charger. Although the voltage is the same, my concern is whether the charge rate is compatible? If anything, I'd think it might take longer to charge than a standard 510 charger? I'm not willing to risk frying one of my chargers, so I figured I'd ask...