FrancoS64

Hi to all, first post here. I've just purchased a Thelema Solo DNA 100C, with a 21700 battery (4000 mAh) without an external batterry charger. It is ok to recharge my battery only via Usb? Someone tells me that could be some problems: specifically because the board hasn't a circut that cut off power when battery is fully charged, and also because it could be overheated. Is that correct? It is better that I buy an external charger?