Amp Rating

[jodeb720]

Ok - I thought I understood electricity ratings (watts, volts, amps).

I know volts and undestand watts is a measure of work - but amps are a capacity.

So when a motor has a rating of 12volts and 12 amps are the amps consumped of amps over an hour (60 minutes)? or is that a constant draw of amps per minute?

If it were watts (it would be volts x amps = watts or in this case 144 watts) - but again, watts are a measure of work - not a capacity or a rating of wires.

This all goes back to me using a 12 volt winch with a 12 amp rating - so if i'm sizing a battery and I expect the motor to run for no more than 10 minutes then i'd use 2 amps if amps are measured per hour.

What am I missing?

Forgive my ignorance, but it's better to ask and understand it than spend money foolishly.

Thanks in advance

Josh

[mike-s]

Watts are not work, they're the rate work is done. Work is measured in joules, which are watt-seconds. But it's common to use watt-hours or kilowatt-hours instead.

One point of confusion is that people commonly say X uses so many amp-hours to refer to work/energy, but that's incomplete. Unstated is the voltage. It's used as a relative term.

Your 12 volt 12 amp motor, when running, uses 144 watts of power. If it runs for an hour, it uses 144 watt-hours of energy.

When working with batteries, it's common to just assume the voltage and only use amps and time. Then it's thought of as a 12 amp motor running for 1 hour using 12 amp-hours.

So, for your winch example - if the winch draws 12 amps for 10 minutes, it will consume 12 amps x 1/6 hour = 2 amp-hours.

[MrWizard]

think of amps as rate of flow
like 1 quart per minute verus 1 gal per minute of water

12 amps is a current/flow rate being used, if that motor runs for 1 hr, you use 12 ampHrs at 12v or 144 watt hrs

water at 1 quart per minutes needs 4 minutes to fill a gallon bucket
while 1 gal a minute will fill the same bucket in 1 minute

10 minutes water run a 1qt per minute is 10qts aka 2.5 gallons of water

you have a 12amp motor, buy a 15amp switch or even a 20 amp switch
you want the switch contacts to have a higher rating than the max draw of the motor, so the contacts do NOT heat up and burn up or get pitted

[Old-Biscuit]

Amps: Amperes, commonly known as amps, measure the flow of electricity as an electric current. Specifically, it measures the amount of electrons that flow past a certain point per second.


PER SECOND


Amp Hour Rating..that is how batteries are rated
if a battery has a rating of 100AH @ 20 Hr rate, then that battery was discharged over 20 hours with a 5 amp load.



12V winch with a 12A rating will use 12 amps per second to run motor at rated speed.

[mrkoje]

I think you are confusing Amp Hour with Amp. Amp Hour is a metric used in storage for how many amps (flow) can be drawn from a battery bank over a course of time before discharged. Amp by it self is current (flow in the common analogy)


On google:

Voltage is measured in volts, current is measured in amps and resistance is measured in ohms. A neat analogy to help understand these terms is a system of plumbing pipes. The voltage is equivalent to the water pressure, the current is equivalent to the flow rate, and the resistance is like the pipe size.
What are amps, watts, volts and ohms? | HowStuffWorks
science.howstuffworks.com/environmental/energy/question501.htm