peterb
Well-Known Member
I'm pushed by the wind turbines thread to ask whether sailing boats have different definitions for amperes compared with the rest of the world?
Can we get this right? Amperes are a measure of current, that is to say instantaneous current. When charging a battery they measure how quickly a battery is charging, not how much charge has been put in.
The scientific unit for charge is the coulomb, the amount of charge resulting from a current of one ampere flowing for one second. For practical purposes this unit is inconveniently small, so we use a unit 3600 times bigger; the charge resulting from one ampere flowing for one hour. For obvious reasons, we call this an ampere-hour.
Amps are an instantaneous thing. Putting it into water terms, amps are the rate at which water (charge) is coming out of the tap; the amount of water that has run into the bucket is the charge in amp-hours.
A unit of amps per hour is almost meaningless; in the water context it would be the rate at which the tap is being turned.
So we measure charge or discharge rates in amperes; we measure the total charge (current x time) in ampere hours. In terms that sailors understand, amp-hours tell us how much we have drunk /forums/images/graemlins/smirk.gif or how much is left in the glass, amps tell us how quickly we are drinking.
Am I being pedantic? Probably. But if we are going to speak the same language, isn't it better if we all define our words in the same way?
Can we get this right? Amperes are a measure of current, that is to say instantaneous current. When charging a battery they measure how quickly a battery is charging, not how much charge has been put in.
The scientific unit for charge is the coulomb, the amount of charge resulting from a current of one ampere flowing for one second. For practical purposes this unit is inconveniently small, so we use a unit 3600 times bigger; the charge resulting from one ampere flowing for one hour. For obvious reasons, we call this an ampere-hour.
Amps are an instantaneous thing. Putting it into water terms, amps are the rate at which water (charge) is coming out of the tap; the amount of water that has run into the bucket is the charge in amp-hours.
A unit of amps per hour is almost meaningless; in the water context it would be the rate at which the tap is being turned.
So we measure charge or discharge rates in amperes; we measure the total charge (current x time) in ampere hours. In terms that sailors understand, amp-hours tell us how much we have drunk /forums/images/graemlins/smirk.gif or how much is left in the glass, amps tell us how quickly we are drinking.
Am I being pedantic? Probably. But if we are going to speak the same language, isn't it better if we all define our words in the same way?
