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The "Classic" charge controller / Re: Why the low power?
« Last post by mike90045 on Today at 02:26:28 AM »
With homebrew panels, you have a lot of failure points that don't exist in factory panels, and
 if your battery has completed bulk, there may not be anyplace for the power to go, so it's simply not harvested
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The "Classic" charge controller / Re: Why the low power?
« Last post by Resthome on Today at 12:41:54 AM »
OK........Just did an experiment.

Disconnected all panels except #2 and #3.

Measurement with only those 2 in parrallel:

V--30, Watts--224, Amps---8.7

Then I hooked 2 and 3 in series.

V--57, Watts--236, Amps---9.4

SO, Not much difference is there???

Maybe there's a bad panel?.........

Will hook/add  them up one at a time and see.....

But the problem obviously isn't the voltage being too low..........lol

z

Some thing is wrong with your system.

P=EI, so if you have 57v x 9.4A = 535.8W
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The "Classic" charge controller / Re: Why the low power?
« Last post by ClassicCrazy on March 24, 2019, 09:04:24 PM »
Are those amp readings short circuit amps when you were testing the panels ?
You change the way the Classic charges in the Mode Menu on MNGP - go to where it says solar and you can use up down arrows to change to Legacy PO .

Larry
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The "Classic" charge controller / Re: Why the low power?
« Last post by Zardiw on March 24, 2019, 08:25:20 PM »
I started with Panel 2 and added 1 panel at a time and noted the readings on the Solar Status Panel software.

When I added panel 8 there was NO change.

Disconnected 8 and added 9.......again no change.

Disconnected 9 and added 1........no change.

Added 8,9,1 and watts went up a little.

Also took Voc/Amp readings on each panel.

Also took a FLuke DC Amps reading.....it was late in the afternoon........but only 16.9 Amps......shoulda been at least twice that.

And each panel has 67 cells..not 66.......fwtfw.

See Images:

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The "Classic" charge controller / Re: Why the low power?
« Last post by Zardiw on March 24, 2019, 06:20:29 PM »
OK........Just did an experiment.

Disconnected all panels except #2 and #3.

Measurement with only those 2 in parrallel:

V--30, Watts--224, Amps---8.7

Then I hooked 2 and 3 in series.

V--57, Watts--236, Amps---9.4

SO, Not much difference is there???

Maybe there's a bad panel?.........

Will hook/add  them up one at a time and see.....

But the problem obviously isn't the voltage being too low..........lol

z
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The "Classic" charge controller / Re: Why the low power?
« Last post by Zardiw on March 24, 2019, 05:02:36 PM »
What is the Voc of your PV array ?  The Vmp will normally be somewhere around 80% of the open circuit voltage.

It is looking like your Vmp or maximum power point voltage is really close to your battery voltage and this would be why it is requiring the input voltage to be so low.

Make sure that Low-Max (LoMax) is ON in the Tweaks menu.  It's the second menu in I think.  Having that on will make sure that the Classic can drop that voltage down closer to the battery voltage.

I would also use the Legacy P&O mode for such a low PV input voltage.

The better answer may very well be to re-wire the panels for higher Vmp and Voc

Let's check the Voc though first.

The PV array cannot put out any higher voltage than the Voc measurement at any given time and the Vmp will always be below that voltage.
That is why Vic is saying that you need higher voltage.

Voc of the Array is 36.2v ......and when it's hooked up it's 33.1v

The Classic is showing an array voltage of 32.7v.

There's about 100Ft run from the panels to the controller.......so losing a volt apparently.

Edit: Lo-Max was already on............How do I set the Legacy P&O Mode?

So far I'm kind of disappointed in the whole MPPT deal.......Right now I'm getting a lousy 538 watts......out of NINE panels.........lol

z
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The "Classic" charge controller / Re: Why the low power?
« Last post by Zardiw on March 24, 2019, 04:54:01 PM »
Here's some individual readings:

Voltage at array: 33.8v

         Voc
PV---Volts---Amps

1---36.2---5.93
3---36.2---7.32
7---35.1---6.44
9---34.8---6.51

Total of just 4 Panels individually: 26.2 Amps

Currently the Classic is showing 17.9 Total Amps at 32V

Pretty pathetic.............

z
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The "Classic" charge controller / Re: Why the low power?
« Last post by boB on March 24, 2019, 04:39:26 PM »
What is the Voc of your PV array ?  The Vmp will normally be somewhere around 80% of the open circuit voltage.

It is looking like your Vmp or maximum power point voltage is really close to your battery voltage and this would be why it is requiring the input voltage to be so low.

Make sure that Low-Max (LoMax) is ON in the Tweaks menu.  It's the second menu in I think.  Having that on will make sure that the Classic can drop that voltage down closer to the battery voltage.

I would also use the Legacy P&O mode for such a low PV input voltage.

The better answer may very well be to re-wire the panels for higher Vmp and Voc

Let's check the Voc though first.

The PV array cannot put out any higher voltage than the Voc measurement at any given time and the Vmp will always be below that voltage.
That is why Vic is saying that you need higher voltage.


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The "Classic" charge controller / Re: Why the low power?
« Last post by Zardiw on March 24, 2019, 04:38:31 PM »
The PV's vary but are all around 32-35V output.

You say I don't have enough voltage .....and the MPPT needs higher voltage.......

Then Why is it putting out MORE watts the lower the voltage.......lol....see the table I first posted..

I'm going to go outside and take some individual readings off these panels and report back.......

z
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The "Classic" charge controller / Re: Why the low power?
« Last post by Vic on March 24, 2019, 04:35:23 PM »
Hi z,

Yes,  any MPPT Controller needs more voltage headroom than  a PWM Controller.

You can wire these PVs as four strings of two PVs for now,   and the Classic will make considerably more poser than you are seeing now.

PWM  CCs have their place.    There is some "cost" in power to run the voltage converter in an MPPT CC,   But,  under many conditions,   a good MPPT CC,   or a GREAT one like the Classic will produce quite a bit more power that would a PWM CC.   AND,   the Classis is the utmost in flexibility and capability  --  so many options,   functions  and Advanced features,   compared to ANY other MPPT CC on the market  (IMO,   but this is all obvious to most).

With 66 cells, you will not be able to fully charge Flooded batteries,   on many days.  This is especially true with cool batteries,   when using high Absorb voltages,  or trying to EQ.

On warm days,   the Vmp falls with the heat,   and so on.    The exact details also depend upon the quality of the PV cells,   glass,   busbars,   etc.

Some of the above are guesses,   due to not knowing the exact specs on your PVs.

Have Fun,   Vic
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