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29-03-2018, 16:50
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#46
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Senior Cruiser
Join Date: Nov 2013
Location: Port Moresby,Papua New Guinea
Boat: FP Belize Maestro 43 and OPBs
Posts: 12,888
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Re: Instant benefit from replacing Solar PWM with MPPT controller?
Quote:
Originally Posted by svlamorocha
Both meanings are the same.. Or do we need a separate thread about math?
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No need, we went through the same thing with the same person in the Amps v Amp hours v Amp per hour thread at great length. Apparently it's just incomprehensible to certain people.
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29-03-2018, 17:04
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#47
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Moderator Emeritus
Join Date: Feb 2011
Location: SF Bay Area
Boat: Islander 34
Posts: 5,486
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Re: Instant benefit from replacing Solar PWM with MPPT controller?
Quote:
Originally Posted by StuM
No need, we went through the same thing with the same person in the Amps v Amp hours v Amp per hour thread at great length. Apparently it's just incomprehensible to certain people.
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Or maybe, just maybe, I just like to argue.....
Or is this abuse. Might be in the wrong room.
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29-03-2018, 17:21
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#48
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Registered User
Join Date: May 2008
Location: puɐןsuǝǝnb 'ʎɐʞɔɐɯ
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Re: Instant benefit from replacing Solar PWM with MPPT controller?
Quote:
Originally Posted by StuM
The difference is only significant if talking about alternating current.
Watts is "real power" , VA is "apparent power".
The real "difference" is the "reactive power" in the circuit.
But it's probably simpler to consider "power factor" for equipment using alternating current. The power factor is the ratio between the two.
Power factor = W/VA
Real power (W) is the power that performs work or generated heat. It is the integral of instantaneous voltage multipled by instantaneous current measured over time, divided by that time. It is NOT easy to measure for alternating currents!
Apparent power (VA) is the RMS voltage multipled by the RMS current. it is useful for calculating wire/fuse sizes etc.
In DC circuits, they are essentially the same.
The important thing is that you need to size circuitry for VA, not W.
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I think you may be confusing Root Mean Square equivalents with VA. They aren't the same. RMS is simply the DC equivalent voltage and current of a sinusoidal AC supply. Power factor, on the other hand, represents the lead or lag between current and voltage in an AC load.
AC power supplies like gensets or inverters are most likely to have a VA rating specified, as this expresses maximum rating of the power source without considering the power factor of any circuit it is connected to.
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29-03-2018, 18:20
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#49
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Senior Cruiser
Join Date: Nov 2013
Location: Port Moresby,Papua New Guinea
Boat: FP Belize Maestro 43 and OPBs
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Re: Instant benefit from replacing Solar PWM with MPPT controller?
No confusion on my part.
It would be more accurate to say that "root mean square" (RMS) is the mathematical method of determining the DC equivalent Voltage or Current.
VA is Vrms x Arms
And that is not only true of sinusoidal waves it is applicable for any alternating wave form.
Whether a power factor of less than 1 is the result of capacitive or inductive loads (lead/lag) is irrelevant to the different between Watts and VA.
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29-03-2018, 18:21
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#50
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Registered User
Join Date: Sep 2006
Posts: 9,398
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Re: Instant benefit from replacing Solar PWM with MPPT controller?
Quote:
Originally Posted by FionaJC
I had a teacher just like you, I proved him wrong more than once and he lost all credibility. I have an Electronics engineering degree, a PhD in computer science, run two companies and he is still a teacher. He also told me that women shouldn't do science, we don't have the brains for it.
You remind me of him a lot. Youre real name isn't Richard Edwards is it?
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Why not prove StuM wrong about kVA then, (or admit he's right) rather than resorting to childish name calling?
At present, it's not his credibility that is suffering.
__________________
"You CANNOT be serious!"
John McEnroe
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29-03-2018, 18:25
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#51
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Registered User
Join Date: Sep 2006
Posts: 9,398
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Re: Instant benefit from replacing Solar PWM with MPPT controller?
Quote:
Originally Posted by StuM
No need, we went through the same thing with the same person in the Amps v Amp hours v Amp per hour thread at great length. Apparently it's just incomprehensible to certain people.
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Maybe instead of Watt hours, we should talk in Joules? That ought simplify things, right?
__________________
"You CANNOT be serious!"
John McEnroe
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29-03-2018, 19:06
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#52
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Senior Cruiser
Join Date: Nov 2013
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Boat: FP Belize Maestro 43 and OPBs
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Re: Instant benefit from replacing Solar PWM with MPPT controller?
Quote:
Originally Posted by 44'cruisingcat
Maybe instead of Watt hours, we should talk in Joules? That ought simplify things, right?
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If you can handle bigger numbers, that may help - but kiloJoules would keep the numbers more manageable.
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29-03-2018, 19:16
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#53
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cruiser
Join Date: Jan 2017
Boat: Retired from CF
Posts: 13,317
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Re: Instant benefit from replacing Solar PWM with MPPT controller?
Quote:
Originally Posted by StuM
Charging LiFePo4, which can take all the current you can throw at them. The optimum case to demonstrate the supeiority of MPPT.
Where you are using solar during the day for charging FLA and to power variable house loads, you will very rarely see anything like that improvement.
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Only if your main use of PV electricity is charging your bank.
Many people have useful work for the "excess" once a lead bank's acceptance drops.
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29-03-2018, 19:22
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#54
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Registered User
Join Date: May 2008
Location: puɐןsuǝǝnb 'ʎɐʞɔɐɯ
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Re: Instant benefit from replacing Solar PWM with MPPT controller?
Quote:
Originally Posted by StuM
No confusion on my part.
It would be more accurate to say that "root mean square" (RMS) is the mathematical method of determining the DC equivalent Voltage or Current.
VA is Vrms x Arms
And that is not only true of sinusoidal waves it is applicable for any alternating wave form.
Whether a power factor of less than 1 is the result of capacitive or inductive loads (lead/lag) is irrelevant to the different between Watts and VA.
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What can I say? If you think RMS and power factor is the same thing then you're confused. Think phase shift.
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29-03-2018, 20:59
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#55
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Senior Cruiser
Join Date: Nov 2013
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Boat: FP Belize Maestro 43 and OPBs
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Re: Instant benefit from replacing Solar PWM with MPPT controller?
Quote:
Originally Posted by Reefmagnet
What can I say? If you think RMS and power factor is the same thing then you're confused. Think phase shift.
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Who said that?
Power factor is the ratio of Watts to VA where Watts is "real power" and VA is "apparent power" (the vector sum of "real power" and "reactive power").
VA is V rms x A rms for alternating current systems.
Added: Since you've introduced phase shift - that is the fundamental cause of reactive power.
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29-03-2018, 21:22
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#56
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cruiser
Join Date: May 2011
Boat: Hitchhiker, Catamaran, 40'
Posts: 1,827
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Re: Instant benefit from replacing Solar PWM with MPPT controller?
While you guys argue your watt hour semantics I will point out that if you are using your mppt controller for solar panels wired in series you might see a bigger gain. But if your panels have shading issues you will need to wire the panels in parallel anyway. I have two 195 watt panels fixed mounted at different angles to each other and one big mppt controller. I would be better off with two smaller controllers.
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29-03-2018, 21:26
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#57
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Registered User
Join Date: Jun 2011
Location: Pacific Central America
Boat: Tayana 37
Posts: 49
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Re: Instant benefit from replacing Solar PWM with MPPT controller?
I am overwhelmed by the talent that my simple enquiry has unleashed.
So, I know I just need another panel......my next dilemma - what colour? (Primary shades only!)
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29-03-2018, 22:54
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#58
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Registered User
Join Date: Aug 2011
Location: Melbourne Australia
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Posts: 2,912
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Re: Instant benefit from replacing Solar PWM with MPPT controller?
Quote:
Originally Posted by Suijin
The there are 24”x60” panels that are 160 watt so I’d start with replacing your panels.
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I just bought a pair of panels, 5 feet by 2 foot 3 inches that are 250 Watts each,
59 inches by almost 27 inches.
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29-03-2018, 23:02
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#59
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Registered User
Join Date: May 2008
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Re: Instant benefit from replacing Solar PWM with MPPT controller?
Quote:
Originally Posted by StuM
Who said that?
Power factor is the ratio of Watts to VA where Watts is "real power" and VA is "apparent power" (the vector sum of "real power" and "reactive power").
VA is Vrms x Arms for alternating current systems.
Added: Since you've introduced phase shift - that is the fundamental cause of reactive power.
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Your answers sound like google copy and paste, even down to the font change. I'm not convinced you really do understand the practical difference of VA and Watts.
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29-03-2018, 23:16
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#60
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Registered User
Join Date: Dec 2013
Location: Malta
Boat: Nicholson 26
Posts: 112
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Re: Instant benefit from replacing Solar PWM with MPPT controller?
Quote:
Originally Posted by john61ct
Watts per hour is commonly used to define watt-hours, but I agree is actually confusing, since watt-hours per unit of time is more precisely correct.
However using such nitpicking to put others down is indeed uncalled for.
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How many Whats? / hour do you get here if you ask a question?
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