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80W power source

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A little 9V alkaline battery can supply almost 80W for a few milli-seconds.
 
A little 9V alkaline battery can supply almost 80W for a few milli-seconds.
Sweet dreams Audio! ;)

9V alkalines have a typical internal resistance of 2.76Ω meaning the most that you can get out of them is 16W for the duration of their capacity.

Dan
 
Yeah, I'm just confused if you have a battery attached to a wire with no physical resistor attached. What would be the current flowing through the wire? Power = Current * Voltage
 
voltage/internal resistance. 3.2A in the case of the 9V, or about 30W dissipated entorely in the battery.
 
A woman gave a speech using a wireless microphone. She began to dance and cry. The spare 9V alkaline battery in her pocket was shorted by a coin and was burning her.

I read somewhere (Energizer?) that a little battery can supply 10A. Maybe an AA Ni-MH cell.
 
A woman gave a speech using a wireless microphone. She began to dance and cry. The spare 9V alkaline battery in her pocket was shorted by a coin and was burning her.

I read somewhere (Energizer?) that a little battery can supply 10A. Maybe an AA Ni-MH cell.
Possibly, but not a 9V
 
That's nonsense, use the 9V battery to charge a capacitor and it will provide 80W for a short period of time.:p
I posted the link to an actual 9V data sheet. 9V/2.76Ω=3.2A into a short circuit from a fresh 9V. P=I²R, R=0, P=0

The most power that you can get is when the load resistance equals the source resistance. The maximum power available is P=V²/R, 4.5²/2.76=7.3W. Now if you are talking energy, that is a different story. You can charge a capacitor to what ever voltage, but that is energy and not power.

Dan
 
A woman gave a speech using a wireless microphone. She began to dance and cry. The spare 9V alkaline battery in her pocket was shorted by a coin and was burning her.

I read somewhere (Energizer?) that a little battery can supply 10A. Maybe an AA Ni-MH cell.

I did that with a metal-tab "C" Nicad. Stuck it in my pocket to free up a hand. Not sure where my brain was at that moment. The pocket was full of coins. :eek: Ouch..ouch...ouch! :(

ken
 
I posted the link to an actual 9V data sheet. 9V/2.76Ω=3.2A into a short circuit from a fresh 9V. P=I²R, R=0, P=0

The most power that you can get is when the load resistance equals the source resistance. The maximum power available is P=V²/R, 4.5²/2.76=7.3W. Now if you are talking energy, that is a different story. You can charge a capacitor to what ever voltage, but that is energy and not power.

Dan
No, the capacitor will increase the peak instantanious power the battery can supply.

Connect a 47,000µF capacitor with a negligible ESR capacitor in parallel the battery, it will charge to nearly 9V in 0.7s. Connect a 1R resistor in parallel and the power dissipation will be 81W at the instant you connect it.
 
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Now you know what Pulsed Power is......:D
 
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No, the capacitor will increase the peak instantanious power the battery can supply.

Connect a 47,000µF capacitor with a negligible ESR capacitor in parallel the battery, it will charge to nearly 9V in 0.7s. Connect a 1R resistor in parallel and the power dissipation will be 81W at the instant you connect it.
Not possible on a bog standard 9V since the internal resistance is almost three ohms limiting the short circuit current to 3A.

At 0.047F and 2.7Ω tau=0.047*2.7=.1269 seconds and 6tau=0.7614 seconds to full charge with a peak current of 3.2A and an exponential RC decay.

Dan
 
No, the capacitor will increase the peak instantanious power the battery can supply.

Connect a 47,000µF capacitor with a negligible ESR capacitor in parallel the battery, it will charge to nearly 9V in 0.7s. Connect a 1R resistor in parallel and the power dissipation will be 81W at the instant you connect it.

I think this is the principle used for flash lights in camera. Am I right? But here he has not mentioned how long he wants 80W power.
 
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