Potential Energy..??

Submitted: Thursday, Feb 11, 2010 at 21:44
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Hmm, well – they thought Mr Voltaic was crackers too…
But would this work?

Suppose (hypothetically) you have a 60W solar panel
Rated as
Max. power: 60 W
Open circuit voltage (V): 22
Short circuit current (A): 4.01
Max. power voltage (V): 18
Max. power current (A): 3.61
So it puts out about 3.5A
Now, this is hardly efficient at charging a 100Ah AGM when camping in the sticks…

So, suppose (also hypothetically) you also have a Battery to Battery charger
This is stated as being a 3 stage charger and is rated as
10v to 15v Input
13.8v to 15v Output 7.5A

Is it feasible/possible to connect the solar panel (with its meagre 3.5A output) to the B2B charger to obtain a 7.5A output???

Or have I had too much red..??

Jedo
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Reply By: pop2jocem - Thursday, Feb 11, 2010 at 22:12

Thursday, Feb 11, 2010 at 22:12
Not 100% sure but if you can get it to work I'm your first customer. (;-))

Cheers Pop
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Reply By: Member - Ed C (QLD) - Thursday, Feb 11, 2010 at 22:15

Thursday, Feb 11, 2010 at 22:15
Whatever it is you're smokin', can you send me some ???

;-))


Confucius say.....
"He who lie underneath automobile with tool in hand,
....Not necessarily mechanic!!"

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Reply By: Lex M (Brisbane) - Thursday, Feb 11, 2010 at 22:16

Thursday, Feb 11, 2010 at 22:16
7.5 amps X 13.8v = 103.5watts.
7.5 amps X 15v = 112.5watts.

You can't get more out than you put in.

without considering losses in system the most you could get out is

4.35 amps X 13.8v = 60 watts
4 amps X 15v = 60 watts


Have another red....
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Reply By: ABR - SIDEWINDER - Thursday, Feb 11, 2010 at 22:21

Thursday, Feb 11, 2010 at 22:21
Hi Jedo

The input is only 15V max so you can't connect the panel without a regulator.

The regulator won't work if it can't sense the battery if you put the DC-DC charger in the way.

It won't work unless you use a very simple regulator but then that will choke the panel anyway.

Regards

Derek from ABR
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Follow Up By: Jedo_03 - Friday, Feb 12, 2010 at 14:08

Friday, Feb 12, 2010 at 14:08
Hi Derek
Yes, I do see these physical limitations:

"The input is only 15V max so you can't connect the panel without a regulator"

I saw that before I posted my OP - but that is a physical design limitation of the B2B device. Perhaps the device could be designed to accept a higher voltage..?

"The regulator won't work if it can't sense the battery if you put the DC-DC charger in the way" - "It won't work unless you use a very simple regulator but then that will choke the panel anyway"

I didn't know that... But, again... Is that a physical limitation of the design specs of current regulators - and could a "regulator" be designed that could still monitor the battery when the B2B is connected - and not choke the panel..?

Just being inquisitive here. No, I'm not on the red...
Jedo



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Reply By: Geoff (Newcastle, NSW) - Thursday, Feb 11, 2010 at 22:35

Thursday, Feb 11, 2010 at 22:35
You've supplied your own answer, "Or have I had too much red..??"
Geoff,
Landcruiser HDJ78,
Grey hair is hereditary, you get it from children. Baldness is caused by watching the Wallabies.

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Follow Up By: Member - Allan B (QLD) - Thursday, Feb 11, 2010 at 22:59

Thursday, Feb 11, 2010 at 22:59
Exactly Geoff.........too much Red!

In the world of physics, you can't get something for nothing.

Even Alessandro Volta knew that!

Cheers
Allan

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Follow Up By: Member - Allan B (QLD) - Thursday, Feb 11, 2010 at 23:28

Thursday, Feb 11, 2010 at 23:28
Oh, and so as to not rewrite history......... Volta was not considered crackers.
He was highly respected throughout his life and was made a Count for his contributions.

Cheers
Allan

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Reply By: Member - Christopher P (NSW) - Thursday, Feb 11, 2010 at 23:11

Thursday, Feb 11, 2010 at 23:11
Thank you for clearing that up for me. Always wondered why you couldn't use a joule thief type circuit (power amplifier) to get more out of a solar panel.
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Reply By: R&J Batteries - Friday, Feb 12, 2010 at 00:00

Friday, Feb 12, 2010 at 00:00
You just described a Maximum Power Point Tracker (MPPT) solar regulator/controller. I try my best to explain what these are and how they work on our website.

You will never achieve greater them the max power current (3.61A) from the panel. Most 'normal' PWM type solar regulators/controllers waste around 30% of this so you will only get about 2.5A in reality from a 60W panel.

Dave
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Follow Up By: Member - Boobook - Friday, Feb 12, 2010 at 06:42

Friday, Feb 12, 2010 at 06:42
Ditto.

You are on the right track Jedo_03

In simple terms a normal PWM type controller can maintain the current but a MPPT controller can maintain the POWER in watts ( ie 80W) byt doing as you described.

Whatever you are drinking or smoking, have more it must be brain food.

MPPT controllers have come down in price significantly lately from $350 - $1000 to not much more than a PWM and less than $100. You would be crazy to buy anything else.

Mandrake ( Solar Steve) on here sells them at a reasonable price

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Follow Up By: Member - Boobook - Friday, Feb 12, 2010 at 06:58

Friday, Feb 12, 2010 at 06:58
Oops wrong button

Mandrake ( Solar Steve) on here sells them at a reasonable price

Solar Steve

also there are tons on ebay here

These should give you an idea on how they work.

What the heck is MPPT

and

MPPT explained

It is pretty neat to see 4.0Amps going into it from the panel and 5.2 amps coming out.

You will get 10 - 30% more charge than a PWM controller. It is especially efficient in th emorning when your batteries are low and the temp is low ( higher solar output voltage). Right when you need it most!!


Also Dave, your comments on the current are not quite correct. You DO get more amps out of the controller than you put in.

In the case of the PWM, the 30% loss occurs as a result of the voltage drop ( from say 19V to 13.8. The current is preserved, ie if you have 3.61A going in, you also have about 3.61A going out.

In the case of the MPPT, it has a DC-DC inverter that preserves the POWER ( at about 95% efficiency).

So if you have a 80W panel that has 19V and 4.21A into the MPPT, you will get an MPPT output of (say) 13.8V and 5.8A. ( less 5% ineffeciency).


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Follow Up By: Member - Ed C (QLD) - Friday, Feb 12, 2010 at 14:14

Friday, Feb 12, 2010 at 14:14
I'm using a Morningstar Sunsaver MPPT controller :)

Still can't get 7.5A from a 60W panel......

So what'm I doing wrong ???
(maybe I'm smokin' the pipe from the wrong end)

;-))

Confucius say.....
"He who lie underneath automobile with tool in hand,
....Not necessarily mechanic!!"

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Follow Up By: Jedo_03 - Friday, Feb 12, 2010 at 14:27

Friday, Feb 12, 2010 at 14:27
Nah Ed...

It was ME who suggested 7.5A - and I was alluding to the output of the B2B device... I don't think R&J or Boobook have suggested that the MPPT device will give you an output of 7.5A from a 60W panel. They do say, however, that you can get a 10% - 30% more charge using an MPPT controller... eg
"So if you have a 80W panel that has 19V and 4.21A into the MPPT, you will get an MPPT output of (say) 13.8V and 5.8A. ( less 5% ineffeciency)."

Jedo
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Follow Up By: R&J Batteries - Friday, Feb 12, 2010 at 14:57

Friday, Feb 12, 2010 at 14:57
Are you sure you 60W panel is actually making 60W? There is a lot of old and/or over-rated panels out there.

A 60W panel on a normal PWM controller will give you about 2.5A.

Using a MPPT regulator will let the panel realise its full potential and give you around 3.5A.

MPPT's don't magically create power. They DO let the panel produce its rated output. However, for small systems typcially found on trailers & vans, the extra cost of the MPPT is hard to justify VS installing another panel.

Dave
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Follow Up By: Jedo_03 - Friday, Feb 12, 2010 at 15:26

Friday, Feb 12, 2010 at 15:26
Hi Dave
Thanks for that info - I'm learning all the time...

The "60W panel" mentioned in my OP is hypothetical. I haven't advanced to solar panels yet.
I'm only going by the figures stated/claimed by various SP sellers. I've no doubt these specs are over-state and don't allow for circuit resistances etc.

My OP just "wondered" (naively) whether a B2B could be run inline with solar power to "boost" charge at the battery. Perhaps such a system could be designed - see my follow up to David Bester's post above.
Jedo
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Follow Up By: Jedo_03 - Friday, Feb 12, 2010 at 15:28

Friday, Feb 12, 2010 at 15:28
Sorry - my apology to Derek Bester...
I did of course mean Derek Bester and not David
Jedo
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Follow Up By: Member - Allan B (QLD) - Friday, Feb 12, 2010 at 15:44

Friday, Feb 12, 2010 at 15:44
Yes Jedo, such a system has already been designed, its called a MPPT Controller.
No need, and no point, in placing a B-to-B charger after it. It would achieve nothing other than additional efficiency losses.

Cheers
Allan

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Follow Up By: Jedo_03 - Friday, Feb 12, 2010 at 20:13

Friday, Feb 12, 2010 at 20:13
Thanks Allan, and all others, for sharing your knowledge...

Allan - no, it probably wouldn't be an 'as-is' B2B charger - more along the lines of a modified MPPT, or something composite, that exploits Ohm's Law...
Volts and Current have direct proportionality:
If R is kept constant, then increasing voltage will increase current. So it got me thinking. How if it was possible to somehow harness that 18/19/20V output of a solar panel and thus increase the output current to a battery..??
Of course, R cannot be kept constant. But it can be factored-in to devices (like CTek factored-in temp sensors). And - there ya go - somebody has already developed the MPPT..!! So I do think it is reasonably feasible to postulate a device that would capture the output voltage of a SP and ouput higher currents. Along the lines of a B2B charger...
I only became interested in 12V 'stuff' after my recent retirement - and after a self-install of an Aux Batt in the rear of my Nissan (Thanks Derek Bester..), so my working knowledge of 12V devices is "in development" which is why I thank all of you for sharing your knowledge and your time. However-though, I believe in innovation and forward thinking. That's how and why we developed to where we are today. Take those college boys who had the idea of linking their gargantuan 'computers' together all those years ago... If they'd taken any notice of the naysayers and 'it can't be done' / 'won't work' brigade then we wouldn't be chatting and sharing knowledge on forums like these...
So it was in that spirit that I posted my OP... Just an innovative thought...
Jedo


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Follow Up By: Member - Allan B (QLD) - Friday, Feb 12, 2010 at 20:30

Friday, Feb 12, 2010 at 20:30
Jedo, I know where you are coming from and I encourage you.

During a lifetime in electrics and electronics I have had my dreams and bright ideas too. Some of them even worked! Occasionally I still have them. But I should quit and just enjoy my retirement. LOL

So keep at it. They even wrote a song in 1972 which suits this .........

"To dream the impossible dream
To fight the unbeatable foe
To bear with unbearable sorrow
To run where the brave dare not go" etc.

Cheers
Allan

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Follow Up By: Jedo_03 - Friday, Feb 12, 2010 at 21:01

Friday, Feb 12, 2010 at 21:01
Thanks Allan...

And the world will be better for this
That one man, scorned and covered with scars
Still strove with his last ounce of courage
To reach......... the unreachable star

I once sang this at a talent quest in the UK and won second prize of 10 pounds.
True...

In my previous working life, as well as my hospital clinical work, I was in a professional group researching the "Neural Basis of Dysphagia" - looking at the anatomy and physiology of the brain involved in the complex neurological control of swallowing, and more particularly what goes wrong when folks have a stroke or brain cancers and the like. Nothing at all to do with 12V 'stuff' - but illustrates my drive for "what if..."
Oh well... Off to Wilcannia tomorrow with the missus to watch the Darling Bash. The river has peaked there and the locals are having a celebration day of floating down the river on home-made 'boats'... Gonna be a sight to see...
Jedo
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Follow Up By: Member - Allan B (QLD) - Friday, Feb 12, 2010 at 21:35

Friday, Feb 12, 2010 at 21:35
Jedo, I can only say.......WOW!

Cheers
Allan

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Reply By: Jedo_03 - Friday, Feb 12, 2010 at 13:55

Friday, Feb 12, 2010 at 13:55
Aye - well...
Nice to see that I'm not right...
But I'm not wrong either...

I confess to being "uneducated" in the 12v realm, but I'm working on that...
My suggestion (above) came from the fascinating (to me) fact that a B2B "booster" can amplify the voltage at the end of a long wire (which is subject to voltage drop) from say 12.4v, to say 13.5v and enable a battery in the van to be charged. Now, I have no idea (as yet) how a B2B "booster" works - only that it does......
Now... I linked the above with another nugget in info regarding solar power that said something along the lines of it being an error to place the regulator close to the panel because the longer feeder line of the regulated supply would then suffer a voltage drop - whereas with the regulator closer to the battery or appliance, the regulator would compensate for the voltage drop between the long wire of the panel to the regulator... Hence there would be less loss...

I also confess to being facetious about the "red"... I do try to be light-hearted when I can. But I am keen to know more about 12v 'stuff' now that I have an Aux batt in the back of the patrol and soon to have 2 more aux batts in the van.
It was interesting to know that there is already a "gadget" (MPPT) that is able to "boost" the output of a solar panel. Thanks for that info. Nice to know that people with enquiring minds are discovering new things all of the time - eh..?? A bit like Volta, who appears to have had learning difficulties as a child (he didn't talk 'til he was 4 and didn't catch up educationally with his peers until he was 14) but went on to excel after that... [The controversy between Volta and Galvani is off topic, so I won't pursue that one...]
Jedo
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Follow Up By: Bonz (Vic) - Friday, Feb 12, 2010 at 21:12

Friday, Feb 12, 2010 at 21:12
Jedo,

The way I understand it is:

Energy is the same thing but it can be in many different forms, kinetic (moving) potential (its going to do something) etc, and every time you change the mode of the energy there are losses (not gains).

So you cant ever get more energy out of something that you put into it, except your wife, but that another story.

.
Time is an illusion produced by the passage of history
.

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