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

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#### Flurng

Dec 29, 2012
21
Every 9-volt battery I've seen has the voltage rating printed right on it, yet none seem to list the wattage, or even amperage rating - so what gives, here?

#### BobK

Jan 5, 2010
7,682
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

#### Alec_t

Jul 7, 2015
3,593
you can pull 450mA for one hour or 50mA for 5 hours, which is the same amount of energy.
For 5 hours read 9 hours.

#### Ratch

Mar 10, 2013
1,099
Every 9-volt battery I've seen has the voltage rating printed right on it, yet none seem to list the wattage, or even amperage rating - so what gives, here?

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

#### davenn

Moderator
Sep 5, 2009
14,271
if its a PP3 type 9V battery, they are just a low current battery up to around 350mA continuous till voltage starts dropping

#### Flurng

Dec 29, 2012
21
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
Hello again, BobK! Thanks for the helpful Info, although I guess what I should have asked is, supposing a device ( transistor, LED, motor, etc...) requires 1 watt; could a typical 9 volt battery power it, and if so, for how long? In the past, I have come across "30 watt" speakers, "5 watt" motors, "1/4 watt" resistors, and so forth - I guess I'm just wondering about the maximum wattage a battery can handle.

Dec 29, 2012
21

#### Flurng

Dec 29, 2012
21
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
Thank you, Ratch, for the info. I do understand the distinction, but I'm still unclear as to exactly how much "power" or energy a battery can provide. Typically, I work with standard, common 9 volt "transistor" style batteries, and I'm just wondering about the maximum power such a source can supply. For instance, I've no delusions that a 9 volt battery could power a jumbo jet, but what about a "10 watt" speaker, or a "5 watt" motor, etc....?

#### Flurng

Dec 29, 2012
21
if its a PP3 type 9V battery, they are just a low current battery up to around 350mA continuous till voltage starts dropping
Thanks, davenn - this is exactly the type of info I'm looking for! Unfortunately, I have no idea what a PP3 battery is, or what type I'm working with - typically, I'll just grab a common alkaline 9 volt, such as a Duracell or Energizer....

#### Martaine2005

May 12, 2015
4,956
Hi Flurng,
The link 'minder' supplied is a PP3 9V battery. Although Duracell don't seem to say 'PP3'.

Martin

#### Ratch

Mar 10, 2013
1,099
Thank you, Ratch, for the info. I do understand the distinction, but I'm still unclear as to exactly how much "power" or energy a battery can provide. Typically, I work with standard, common 9 volt "transistor" style batteries, and I'm just wondering about the maximum power such a source can supply. For instance, I've no delusions that a 9 volt battery could power a jumbo jet, but what about a "10 watt" speaker, or a "5 watt" motor, etc....?

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

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