i really like the 500mah output ego charger if you can find one . there are shipped with thehigh capacity ego T cells , the 2500 mah and up use a 500 mah charger . they ship with one of these . mine fried out but i had found one on the pavement before i was even vaping so ... i ordered another high cap ego t , to get a charger .with 500 mah out . they work bit faster . i typically get green light with the 500 then switch over to a 420 mah and top it off after letting the battery cool down for a few minutes . this works very very well . clean the contacts as well . i really do not use usb ports on laptops or pc's though . i prefer dedicated charger ac adapters or even a mulitple outlet usb hub with a hefty 3.5 amp power supply . my unit is rated a 1a on each port max ... i typically charge 2-4 egos at once on this . you can find a " ego super charger" which is indeed 4.2 volts but 500 mah out , it runs 8 dollars plus shipping . there is one company selling this but . man that is a bit steep for what you get .
i also read that if the battery is adjustable or a twist style , turning the battery up to its highest output setting may be the wise choice for charging so , this is what i have done , but ... i have never tried it the other way or read this in the non exsistant instructions . ha . thanks china.
we have soldered a few of these as the wires break sometimes as well , but ... , we have a bit of a clue what we are doing ( my wife solders too ) we enjoy blindly hacking stuff all the time , for many years but we certainly do not claim to be pro tech or expert types . just common sense / saving a buck really . i never charge un attended . never . i do monitor for heat as well .
be safe .