Calculating how long batteries would last?

Sorry, I didn't read it very carefully. I believe the laser light is rated at 5mW. If it is 5MW, then the batteries won't be able to run it. So, each battery stores 1.5 x 130 = 0.195 Wh of energy. 0.195/ 0.005 = 39h 3 x 39 = 117 h So, one battery can run the laser for 39 hours, all 3 run it for 117 hours.

"i thought 130mAh is the amount of energy" no, watt-hours are energy. Amp-hour are not. multiply by 1.5 volts and you get watt-hours. 130 mA-hour means the battery can supply 130 ma for an hour or 260 mA for half an hour of 65 mA for 2 hours, etc. that 5 MW light will last a tiny amount of time. 5 MW is 5 million watts, a huge light. voltage is 4.5 volts so current is about 1 million amps, flatly impossible. edit, perhaps you mean 5 mW ? but the M is there, and you used m for the amp-hour rating. .

I think the one cell and three cell is a trick question as the laser likely needs all three cells to light. So 4.5 volts at 5 mW is 1.11 milliamps, so about 117 hours if the laser can extract all the mAh of the 3 cells. It is possible that the laser uses 5 mWh and the current control circuit uses 4 mWh average: 4.5 volts at 9 mW is 2 milliamps, so about 65 hours. One cell will run the laser for zero hours. Neil

I think the one cell and three cell is a trick question as the laser likely needs all three cells to light. So 4.5 volts at 5 mW is 1.11 milliamps, so about 117 hours if the laser can extract all the mAh of the 3 cells. It is possible that the laser uses 5 mWh and the current control circuit uses 4 mWh average: 4.5 volts at 9 mW is 2 milliamps, so about 65 hours. One cell will run the laser for zero hours. Neil

"i thought 130mAh is the amount of energy" no, watt-hours are energy. Amp-hour are not. multiply by 1.5 volts and you get watt-hours. 130 mA-hour means the battery can supply 130 ma for an hour or 260 mA for half an hour of 65 mA for 2 hours, etc. that 5 MW light will last a tiny amount of time. 5 MW is 5 million watts, a huge light. voltage is 4.5 volts so current is about 1 million amps, flatly impossible. edit, perhaps you mean 5 mW ? but the M is there, and you used m for the amp-hour rating. .