Metric Way of Stating Battery Capacity
- Thread starter Oldtoad
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Aaron_85
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Ampere IS the SI defined unit of current.
Another way is coulomb. 1 coulomb is 1 amp second so 280ah is 1MC in SI base units.
I guess you could state it that way, but it doesn't mean much in everyday use.
If we factor in voltage and quoting total energy, our 896 watt hours becomes 3.2MJ in the base SI unit of energy. Also a useless unit for everyday use.
Another way is coulomb. 1 coulomb is 1 amp second so 280ah is 1MC in SI base units.
I guess you could state it that way, but it doesn't mean much in everyday use.
If we factor in voltage and quoting total energy, our 896 watt hours becomes 3.2MJ in the base SI unit of energy. Also a useless unit for everyday use.
For most electricity measurement, W-hr is used. Or kW-hr- which is what is used for homes.
But like Aaron said, Amp is the SI unit- for some reason, batteries use A-Hr as their capacity measurement instead of W-hr. Seems like at some point it was easier to spec a unit for it's current pull than it's power pull- even though the overall measurement is the same thing when voltage is used.
Keeping a power*time as the unit is slightly more straight forward, as you can understand how much power a unit uses and how long you will use it, as opposed to the actual energy unit of Joule.
Given when all of the development for electricity took place, there was no time where a non-SI unit took place. Still is a lot of odd uses of SI units....
But like Aaron said, Amp is the SI unit- for some reason, batteries use A-Hr as their capacity measurement instead of W-hr. Seems like at some point it was easier to spec a unit for it's current pull than it's power pull- even though the overall measurement is the same thing when voltage is used.
Keeping a power*time as the unit is slightly more straight forward, as you can understand how much power a unit uses and how long you will use it, as opposed to the actual energy unit of Joule.
Given when all of the development for electricity took place, there was no time where a non-SI unit took place. Still is a lot of odd uses of SI units....
Mike Jordan
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Wait...whaAat?!? Post the youboob metric vid. That sounds entertaining
Q-Dog
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I've heard many people talk of using lithium/LiFePo4 to replace a metric crapload of lead batteries.
Brendon Tait,Wait...whaAat?!? Post the youboob metric vid. That sounds entertaining
Mike Jordan
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Quite disappointed. I was looking forward to learning something new
Hedges
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You could say a 280 Ah 3.2V cell stores 3.2 mega-Joules of energy.
Joule - Wikipedia
NobodyOfNaught
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I assume my metric you mean SI units, metric is just a system of dividing units, you could use the metric system to divide imperial units with kilo-inches and micro-pounds.
SI units are an international standard of units that use the metric system for division.
The amp is an SI unit just like meter and an amp hour is a derived unit much like kilometers per hour.
The base unit for energy is joules, however it's easier for most people to think in a unit like watt hours because we know how much power a device uses and an hour is an easy to comprehend length of time.
With Batteries we typically think in amps because within our systems the voltage basically remains the same but the amps are what is different depending on the device. And since we mostly size wire and fuses based on amperage it's just easier to think about everything in amps.
SI units are an international standard of units that use the metric system for division.
The amp is an SI unit just like meter and an amp hour is a derived unit much like kilometers per hour.
The base unit for energy is joules, however it's easier for most people to think in a unit like watt hours because we know how much power a device uses and an hour is an easy to comprehend length of time.
With Batteries we typically think in amps because within our systems the voltage basically remains the same but the amps are what is different depending on the device. And since we mostly size wire and fuses based on amperage it's just easier to think about everything in amps.
A 280Ah lead acid battery has no where near the ca-ching of a 280Ah LifePo4.
I know battery manufacturers fib about what they got, like most men trying to get lucky. Except us studs, here on the diysolar forum, of course.
Just trying to wrap my head around this re-volting electron flow. Thanks all.
I know battery manufacturers fib about what they got, like most men trying to get lucky. Except us studs, here on the diysolar forum, of course.
Just trying to wrap my head around this re-volting electron flow. Thanks all.
DerpsyDoodler
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Jiga....that’s jigawatts, Marty. Great scott!
Mike Jordan
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Ah is just a derivative of V/Wh so, a 280Ah LiFePO4 cell is 896Wh, so 4 of them in series would be 280x12.8 or 3.584KWh
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