Impress your friends by using correct units and abbreviations

[rmaddy]

Shouldn't "V - volts, a unit of voltage.", be a unit of Electromotive force?

I tweaked it to say "electric potential.

For the Wikipedia entry on "Volt":

The volt is the derived unit for electric potential, electric potential difference (voltage), and electromotive force

"A battery's voltage is measured...", be, A battery's EMF is measured in volts - V?

A battery has a voltage (electric potential difference).

 

[rin67630]

I tweaked it to say "electric potential.

For the Wikipedia entry on "Volt":

The volt is the derived unit for electric potential, electric potential difference (voltage), and electromotive force


A battery has a voltage (electric potential difference).

Without intensity, a plain voltage will only generate a very low force (excepted at kilovolts on your hair)

 

[Larry Oswald]

So what is C ?

Capacitance or the speed of light ?

For sure and sometimes. Is mass m or M? The gravitational constant is always G.

 

[32 volt boater]

AC vs A/C - AC is alternating current. A/C is air conditioning

Thanks.

 

[Benmanji]

So what is C ?

Capacitance or the speed of light ?

c (lowercase) is a symbol for the speed of light (under specific conditions). C (uppercase) is the symbol for a coulomb, a unit of electric charge.

 

[Warpspeed]

We need a bigger alphabet.

 

[wattmatters]

We need a bigger alphabet.

That's why we use the Greek alphabet so much.

 

[midahar]

The following are common units and their abbreviations. Note that unit abbreviations are case-sensitive. While some units can be understood when written incorrectly, some have a completely different meaning if the wrong case is used. Avoid any possible confusion or ambiguity and use the correct case.

A - amps, a unit of electric current. Named after André-Marie Ampère.
V - volts, a unit of electric potential. Named after Alessandro Volta.
W - watts, a unit of power. Named after James Watt.
Ω - ohms, a unit of electrical resistance. Named after Georg Ohm.
h - hours
k - kilo (SI prefix for 1000)
K - Kelvin, a unit of temperature. Named after William Thomson, 1st Baron Kelvin. Not really relevant in solar discussions.
m - milli (SI prefix for 1/1000)
M - mega (SI prefix for 1000000)

Current is measured in amps - A
A battery's voltage is measured in volts - V
A battery's current capacity is measured in amp hours - Ah
A battery's energy capacity is measured in watt hours - Wh. Wh is simply Ah x V. Many times it is shortened to kilowatt hours - kWh. Example: 5120Wh or 5.1kWh.
An inverter is measured in watts - W. Many times a value is shortened. 4000W can be written as 4kW. Really large systems could be in megawatts (MW) or even gigawatts (GW). Small electronics might be measured in milliwatts (mW).
A wire's resistance is measured in ohms - Ω. Many times the resistance is very small such as 0.002Ω commonly written as 2mΩ (two milliohms).

--------------------------

AC vs A/C - AC is alternating current. A/C is air conditioning

--------------------------

While not a unit, one common abbreviation that should be written correctly is for Lithium Iron Phosphate batteries. The correct written form is LiFePO₄ though most people find LiFePO4 is much simpler to type. LFP is a shorthand abbreviation understood in the context of this forum when discussing batteries.

Incorrect abbreviations would include LiFePO (lithium iron phosphorus oxide), LiFePo (lithium iron polonium), LiFePo4 (lithium iron tetra-polonium), LiFeP04 (using a zero instead of a capital O), LiFe (lithium iron), LifePo4 (wrong case on the F and O).

Note that there is a lithium-ion polymer battery typically written as LiPo. That is not at all the same as LiFePO₄. You do not want to confuse the two types. Though both of those types are specific examples of the more general lithium-ion (Li-ion) batteries.

I use Google speak to to take your diction you don't know what you're going to get it sometimes goes to Mars and gets the strangest things but that was interesting about l i f e p04 I hadn't noticed that it was a zero instead of an o

 

[Supervstech]

I use Google speak to to take your diction you don't know what you're going to get it sometimes goes to Mars and gets the strangest things but that was interesting about l i f e p04 I hadn't noticed that it was a zero instead of an o

Incorrect. It is PO for the molecule of Phosphate PO4
ONLY THE 4 IN THE NAME IS A NUMBER. Li is for Lithium, Fe is for Iron, PO4 is for the molecule phosphate.

Phosphate - Wikipedia

en.m.wikipedia.org

 

[Housingsoft]

The following are common units and their abbreviations. Note that unit abbreviations are case-sensitive. While some units can be understood when written incorrectly, some have a completely different meaning if the wrong case is used. Avoid any possible confusion or ambiguity and use the correct case.

A - amps, a unit of electric current. Named after André-Marie Ampère.
V - volts, a unit of electric potential. Named after Alessandro Volta.
W - watts, a unit of power. Named after James Watt.
Ω - ohms, a unit of electrical resistance. Named after Georg Ohm.
h - hours
k - kilo (SI prefix for 1000)
K - Kelvin, a unit of temperature. Named after William Thomson, 1st Baron Kelvin. Not really relevant in solar discussions.
m - milli (SI prefix for 1/1000)
M - mega (SI prefix for 1000000)

Current is measured in amps - A
A battery's voltage is measured in volts - V
A battery's current capacity is measured in amp hours - Ah
A battery's energy capacity is measured in watt hours - Wh. Wh is simply Ah x V. Many times it is shortened to kilowatt hours - kWh. Example: 5120Wh or 5.1kWh.
An inverter is measured in watts - W. Many times a value is shortened. 4000W can be written as 4kW. Really large systems could be in megawatts (MW) or even gigawatts (GW). Small electronics might be measured in milliwatts (mW).
A wire's resistance is measured in ohms - Ω. Many times the resistance is very small such as 0.002Ω commonly written as 2mΩ (two milliohms).

--------------------------

AC vs A/C - AC is alternating current. A/C is air conditioning

--------------------------

While not a unit, one common abbreviation that should be written correctly is for Lithium Iron Phosphate batteries. The correct written form is LiFePO₄ though most people find LiFePO4 is much simpler to type. LFP is a shorthand abbreviation understood in the context of this forum when discussing batteries.

Incorrect abbreviations would include LiFePO (lithium iron phosphorus oxide), LiFePo (lithium iron polonium), LiFePo4 (lithium iron tetra-polonium), LiFeP04 (using a zero instead of a capital O), LiFe (lithium iron), LifePo4 (wrong case on the F and O).

Note that there is a lithium-ion polymer battery typically written as LiPo. That is not at all the same as LiFePO₄. You do not want to confuse the two types. Though both of those types are specific examples of the more general lithium-ion (Li-ion) batteries.

Thanks, Maddy.

 

[Oscars]

This discussion was super helpful for me. Thanks guys n gals.

 

[fblevins1]

All that being true, why is ohms law stated as E over I times R? Why not V over A times Ω? Yea....dats wud I taught. (oYo) I'll show myself to the door.

 

[KITROBASKIN]

Such a fun and informative thread, with members expressing logic, convention and a touch of beauty.

What about the company Victron Energy using VA instead of watts? Just how relevant is it for most of our uses? Could it be considered by some to be an affectation? Are there other companies choosing to use VA over watts (other than specifically differentiating circuitry affects)?

 

[MisterSandals]

What about the company Victron Energy using VA instead of watts?

I suspected it was either a European thing or made more sense for equipment that spans the 50hz/60hz and 230V/240V realm.

I liked it because it made me stop and think a little more about the numbers and units since its a different way of looking at things.

 

[Warpspeed]

VA reactive power is highly applicable to inverters, far more so than watts.

Power is the rate of doing work. You lift up a weight over a certain distance, in a certain time, and REAL power is needed to do that.
When the same weight drops or is lowered over the same distance that stored power is fully recovered.

Reactive power is like the guy in the picture below. Electrical energy is stored then released by either a capacitor or an inductor. Its like the energy stored and released in a mechanical spring.

Try telling the guy below that the strength of the spring makes absolutely no difference, because all of the energy in the spring is fully recovered.

If your inverter is working into a highly reactive load, its going to sweat and suffer like the guy, even though no real power is being consumed.
No heat is generated in the reactive part of the load, and no real power dissipated either. But your inverter still has to fight that reactive load, and maybe supply a very high circulating current that can even blow up your inverter in attempting to do so.

Its why commercial alternators are always rated in kVa and not watts.
Strictly speaking, inverters should be rated in kVa as well.

 

[fblevins1]

I suspected it was either a European thing or made more sense for equipment that spans the 50hz/60hz and 230V/240V realm.

I liked it because it made me stop and think a little more about the numbers and units since its a different way of looking at things.

All I know is most VA meters seem to be more representing voltage times current, maybe even simple math function, but...a wattmeter can go all nuts on you if your measured current is not in phase with the voltage, when I was calibrating power quality analyzers, I had to make sure my two sources were phased locked to each other in order for the wattmeter to read properly, not so much a problem with VA meters. Now I don't have to worry about phase because my new calibrator is dual output so my current and voltage outputs are automatically in phase. Fun fact, when I calibrate power quality analyzers, the unit may display 240,000 watts, but I am lying to it. I might be pulling pulling 4 watts max out of my calibrator.

 

[wattmatters]

What about the company Victron Energy using VA instead of watts? Just how relevant is it for most of our uses?

Victron are doing the right thing since VA and watts are not the same thing.

VA only equals watts when the AC voltage and current are both in phase. This is the case when circuit loads are resistive only.

When voltage and current are out of phase (which is common on any AC circuit with inductive loads or capacitive elements) then VA <> W.

 

[fblevins1]

Victron are doing the right thing since VA and watts are not the same thing.

VA only equals watts when the AC voltage and current are both in phase. This is the case when circuit loads are resistive only.

When voltage and current are out of phase (which is common on any AC circuit with inductive loads or capacitive elements) then VA <> W.

A few years ago, your username would have meant nothing more to me than a play on words. But after being forced to dive into the microgrid academic world, I love using wattmeter's on both the AC and DC sides, I hate having to continuously calculate VA from a voltmeter and current meter and prefer to just monitor watts on both sides, although I guess DC is exclusively VA, expressed in watts? I find watts to be the most important unit of measure when determining solar budgets, (how much power from the PV's, How much power from the batteries, how much power from the loads) I wish AWG was stated in watts per application. Anyway....your username...very correct.

 

[timselectric]

I wish AWG was stated in watts per application.

It can't be because it can be used with a wide range of voltages. It's cross section only limits the amperage it can carry.

 

[wattmatters]

although I guess DC is exclusively VA, expressed in watts

Power factor only applies to AC. There is no phase on DC, only on AC.

Hence VA = W on the DC side.

I find watts to be the most important unit of measure when determining solar budgets, (how much power from the PV's, How much power from the batteries, how much power from the loads)

While using watts and watt hours is good for making assessment for sizing system generation and storage capacity, VA (and reactive power) is something you need to be very aware of especially if you are powering large inductive loads such as motors.

You can find your inverter would appear to have sufficient rated capacity, when for an inductive load it may not.