Solar Panel Query --- advice needed ...

The picture tells a slightly different story:
200 watts delivering 12 Amps to the Solar regulator
5 Amps charging 200ah of AGM's @ 14.3v

The solar system is mounted flat on the roof, so obviously it's not pointing in the correct position to gain anything like optimum performance, but it's not an elcrapo low performance solar system, maybe that is why it works reasonably well.

I assure you the pic was not taken on a chilly temp day, so if 12 Amp is about 70% of the best performance from a 200 watt Solar system I'm more than happy :-)

Image Could Not Be FoundMaîneÿ . . .

Mainey

If you are getting 12 A into the controller and only 5 A into the battery I think there is something wrong. There are 3 possibilities I can think of:

1. Instrument error. One of the meters is way out.

2. There is a 7 A load on the system and this is not being taken into account.

3. The controller is wrongly installed. This is quite common with these controllers that were originally designed for positive earth installations (telecommunications systems.) The 3 negative terminals are all at different potentials where as the 3 positive terminals are connected together. If you read the technical articles in the Wanderer you will see many examples of where solar installers have stuffed up the installation in motorhomes.

PeterD

Peter,
(1) No, there's nothing wrong with any of the instruments
(2) Yes, there could be a 7 Amp load on the 14.3v battery system (probably not)
(3) No installation problems either, I installed it :-)

The more obvious solution (to me) is:
maybe, just maybe, the 14.3v battery system is close to fully charged and the fridge is *not* running.
The Solar regular is obviously doing it's job of regulating the current going to the 14.3v battery system.

Just because the Solar system can collect 12 Amps, does not automatically mean they are *all* sent to the battery system all of the time, that would soon destroy any battery system.




This picture clearly shows the fridge is running
3.1 Amps from the 13.1v battery system
4.9 Amps direct from the Solar system
(~8 Amp draw) Image Could Not Be FoundMaîneÿ . . .

The 70% efficiency comes from a standard regulator, not the Panels.

As per Mainey's example, he is getting 12A from 200W of solar panels. At say 17V that makes sense. But the output of the regulator, ie the usable power into the batteries the voltage is 13.1 on the voltmeter. 13.1 x 12A is 157watts.

157w divided by 200w = 78% efficient.

Mainey, the 12A doesn't just dissapear, 7.1A must be going to the load.

Steca PR1515 - PWM shunt regulator.

The extra 7.1A goes to heat in the regulator.

This explains how an analogue shunt regulator works.
http://www.waynecard.com/index.php?page=solar-shunt-charger

A PWM regulator works the same but has some more smarts controlling the shunt circuit.

So your getting 12A from the solar panel and 7.1A is doing nothing but heating up the shunt in the regulator. 100watts +. The regulator should be getting quite warm.

Ahh yes. Forgot about that, thanks Lex.

Lex,
Yes the Steca regulator is PWM controlled !!
Steca PWM technical specs the Steca regulator does not even get warm.

You can't seriously believe the Steca reg is simply wasting 7.1 Amps "heating up the shunt in the regulator" on any *permanent* basis, that just does not happen.
UNLESS-> your suggesting it's being "regulated" by the Steca regulator so it will not send the full 12 Amps to an already fully charged battery system, with-out actually using the word "regulate" ??


consider this:
will a Toyota 100 Amp Alternator, at ALL times, supply the full 100 Amps to the battery ?
or
will a Ctek 50 Amp battery charger, at ALL times, supply the full 50 Amps to the battery ?

-> of course not
reason being the 100 (or 50) Amps is "regulated" by the appropriate device
exactly the same as Steca Solar regulator "regulates" Solar power to the battery.



The picture posted above clearly shows what's happening:

Solar system delivering 12 Amps to the Solar regulator
Solar regulator sending just 5 Amps to *TRICKLE CHARGE* the 14.3 Volt battery system

Easy to see and understand, no tricks, no gimmicks and no problems


This picture (below) clearly show 10 'Plus' (cause it can't show 12) Amps is charging the battery system, however with the 7 Amps you claimed to be "wasted" heating up the shunt, takes the total to 17+ Amps minimum, from a 200 Watt solar system - I believe this pic shows your numbers & ideas don't add up to a credible explanation as I'm sure you will also agree, it's impossible to get 17+ Amps from a 12v, 200 watt Solar system.
Image Could Not Be FoundMaîneÿ . . .

Mainey, I don't think Lex is implying that the Stecca will always use 7A internally. He is saying that as a shunt type charger, the "excess" available current is dumped to ain internal load to control the output. If the external load requires more current then less will be diverted, or shunted to the internal load. If your charge requires the full 12A then the charger simply won't divert the 7A ( which as you correctly point out isn't available).

I don't think this is a comment on Steccas wasting 7 (or whatever at the time) amps, it is just the way that type of charger works.

At the time you took the picture you had 12A from the solar panel and 5A going into the battery. If you had no other load then where do you think the missing 7A is going? It has to go somewhere.

The solar regulator has to waste the excess current. That's how a shunt charger regulates.

How much it wastes at any time will be the difference between what the solar panel is putting out and what it needs to charge the battery appropriately at the time.

All regulators have to waste or limit power somehow when the solar panel is outputting more than needed. I believe solar panels don't like the load being switched when working, My panels have a warning about this. Therefore the common way of regulating is by switching the excess current to an alternative load internally, (a shunt). The solar panel doesn't see any difference from it's end so it's happy.

With fridge disconnected from the 12v circuit, the battery shows 12.8v
with (about) zero Amps going to it from the 8.6 Amps available at the time
obviously because they were being "wasted" somewhere else

Where these "wasted Amps" go or hide, is not the point.

Just like the scenario above of the 100 Amp Toyota Alternator and Ctek 50 Amp battery charger, not all the Amps available from either of these devices are sent to the battery either, because they are also "regulated" efficiently, hence the terminology 'trickle charge' is applied, because only a small percentage (%) is sent to the battery as it reach's the point of being fully charged Image Could Not Be FoundMaîneÿ . . .

Mainey an alternator or Ctek or similar charger are not similar examples. If you have a 100A alternator that is connected to a battery charging at 5A, and nothing else is connected, the Alternator only outputs 5A. Same for the charger.

Can we agree to disagree, as I believe they are similar examples, reason being all three devices are very capable of putting out much higher current than is sent to the battery and in some instances more than the battery can handle consistently.
The current from all three devices must first travel via a *regulator* before it goes to the battery.
The total current produced by any device mentioned above does not go direct to the battery with-out first being regulated in some way.

You say: "If you have a 100A alternator that is connected to a battery charging at 5A, and nothing else is connected, the Alternator only outputs 5A. Same for the charger"

Are you sure?
if the Alternator is rated @ 100 Amps, isn't it's output "regulated" by the Alternator's *regulator* down to the 5 Amps you mention ?
Same with the 50 Amp battery charger, it's output is "regulated" - hence the terminology "trickle charge" and "boost charge" etc.

(where the 'missing' current goes to when regulated is not relevant, as it does NOT go to the battery)

Maîneÿ . . .

The difference is that a ctek or an alternator is "pre-regulated". That is they produce only the current needed as controlled by the INTERNAL regulator. They may be capable of producing more than needed but the regulator controls how much is produced.

A solar panel is usually "post-regulated".
It produces whatever it is capable of in the current solar conditions and the EXTERNAL regulator then disposes of that current as it sees fit.

The other important issue is that Regulators don't regulate current. They regulate voltage. The current is a result of the (regulated) voltage and the load. You can have current limiters but that is totally seperate. A 100A alternator means that it can supply 'up to' 100A at the regulated voltage.

That depends on what you mean by "regulate".

For example a battery charger controls the current dependant on the voltage measured at the battery. The voltage at the battery terminals is dependant on a number of things, eg state of charge - current input - internal impedance to name a few.
The charger controls the current into the battery while monitoring the battery voltage for what the charger deems appropriate for it's charging program.
Does it regulate the voltage? Maybe, but they do it by controlling current and thereby indirectly controlling voltage

An simple alternator regulator controls battery voltage by controlling field strength which controls the current supplied by the alternator and reduces field strength to keep the voltage down to a safe level.
Does it regulate the voltage? Once again it controls the current.

Am I being pedantic?

A 100A alternator means that it can supply 'up to' 100A at the regulated "voltage."

Missed that point. A 100A regulator means that it can supply a max of 100A.
This is dependant on the physical characteristics of the alternator, field strength - impedance of windings etc.

The voltage at that time is dependant on the external connections, EG short circuit a 100A alternator and it will supply 100A at zero volts (but probably not for long).

I'm being pedantic again. :-)

I guess so Rex,

I would have thought that a 100A alternator was designed with the physical characteristics of the alternator, field strength - impedance of windings etc to cope with a 100A load at it's rated output. That's why it is a 100A alternator yeah?

And sure, a short circuitwould mean zero volts, output. A short circuit across a nuclear power station would mean zero volts by definition too, also for a very short time. Maybe we are at crossed purposes REx, my point was that a 100A alternator will output 0 to 100A ( under rated loads).

Of all the interesting replies above, you are the only one to suggest the quickest and simplest way, measure the short circuit current.

A lot of people seem to be not aware of that it is quite OK to short circuit the panel with an Amp meter, no regulator or battery need to be involved. Actually, do NOT connect anything other than the Amp meter when doing this test. And DO set the Amp meter to the expected DC amp range if its a multimeter.

My only difference in opinion with the answer above is the comment:
"When connected to a battery this output voltage will be about 17v"
When one connects a solar panel directly to a battery one measures the battery terminal voltage at that time, no more or less. 17V would certainly ring alarm bells if I measured that.

V8 Troopie posted:
my difference in opinion with the answer above is the comment:
"When connected to a battery this output voltage will be about 17v"
When one connects a solar panel directly to a battery one measures the battery terminal voltage at that time, no more or less. 17V would certainly ring alarm bells if I measured that."

Hi V8

Probably did not make it clear,when I said that " you will not be able to read that".
Because as you say you will be reading the bat voltage which will be a bit higher than the state of charge, but certainly should never be higher than 14.5<15v, depending on battery type.
The point I was trying to make was that the panel max output[watts] is usually based @ about 17v for 36cell panels.
Many panel do have a graph on the back showing the output volts versus current.
They are constant current devises which means they will give virtually the same current outpt under load from short circuit [0v]TO loads with an equivalent impedance of about 3.8ohms @ which the output volts will be approx 17v[max watts]
This of coarse based on sufficient & constant sun intensity.l

yes, and "This of coarse based on sufficient & constant sun intensity" differs greatly from hour to hour, hence the reason we get sooo many different Amperage reading at different times of the day

Maîneÿ . . .

Hi

Of course if the bat voltage is 14.5v@ 4.5 amps input, " watts " INPUT from the solar panel is 65.25w, about 81.5% of its rated capacity[watts] for an 80w panel.

Maîneÿ . . . posted:
yes, and "This of coarse based on sufficient & constant sun intensity" differs greatly from hour to hour, hence the reason we get sooo many different Amperage reading at different times of the day
Maîneÿ . . .

Hi Mainy

Very very true.

High intensity light say reflected from clouds can actually give a significant increase in current < about 10%

I wonder that too, but I'm not going to denigrate a product with unknown specifications.
The numbers quoted are not totally relevant to real life performance in the bush.

Would like to see an 80 Watt compared to a BP 80 Watt, as a direct comparison, however from the East coast over here to the Best coast is a long way to run extension cables.


Maîneÿ . . .

Hi
I believe that some are not rated @ load conditions as above but @ open circuit volts.
You need to ensure you are getting applesfor apples specs wise.

Have a look at my last ebay purchase to add to the other six I already bought from this guy a couple of years back.

Wazzaaaa

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