To charge money, or to charge a battery, or indeed to charge against the opposition?
gwefru is to thrill, be thrilled, and then by extension to galvanise, to become electrified. Also nowadays used for charging a battery.
'Electric Mountain', a hydro-electric power storage facility at Llanberis which provides near-instant call-off power supply for the UK National Grid, is Mynydd Gwefru. (Well worth a visit!)