So, how many "watts" is a 9-volt battery?

Generally batteries are rating Ah mAH etc.
The better known manufacturers usually show the specs.
http://ww2.duracell.com/media/en-US/pdf/gtcl/Product_Data_Sheet/NA_DATASHEETS/MN1604_6LR61_US_CT.pdf
M.

 

The current that a battery can supply to a short circuit is not well controlled and drops rapidly with use. In other words, you might initially get 2 or 3 amps from a 9V battery, but only for a few minutes.

The capacity rating of a battery tells you how long you can pull a given current from the battery. A typical rating for a 9V is 450mAH. Which means you can pull 450mA for one hour or 50mA for 5 hours, which is the same amount of energy.

But even that is misleading. At higher current draws, a battery cannot supply the same amount of energy as it can at lower currents.

Typically, an ordinary battery should not be used at higher current than the capacity, but there are exceptions. The rating is usually given to a usage of much more than one hour, often 20 hours is used.

Bob

 

For 5 hours read 9 hours.

 

Watts are not a quantity that you can put into a battery. Wattage is a rate of energy transference. If you want to know how much energy is in a battery, don't ask for its wattage.

Ratch

 

Hi Flurng,
The link 'minder' supplied is a PP3 9V battery. Although Duracell don't seem to say 'PP3'.

Martin

 

The amount of energy that can be obtained from any battery is determined by the rate it is de-energized. If de-energized slowly, then more energy can be extracted. There are battery manuals that give the specs of various batteries.

Ratch