Hello together, I have a battery (Green Cell AGM lead battery) with 12V/12Ah and an H7 halogen lamp (XELORD) with 12V/55W. If I would only connect the lamp to the battery, then 1) If the current in the circuit is about 4.58A: P = U * I => I = P / U => I = 55W / 12V = 4.58A 2) If the battery lasts about 2 hours 37 minutes: 12Ah / 4.58A = 2.62h (Decimal) or 2 hours 37 minutes I would have two questions: 1) Are my calculations correct or have I overlooked something ? 2) Is that correct that no Resistor is necessary in this circuit? And, if so, why? Wouldn’t the lamp burn out immediately without Resistor? 3) I connected two 9V block batteries (Varta) in series and tried to make the o.e. lamp glow. But that didn’t work. Can someone please explain to me why this didn’t work? Thank you in advance!