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what's wrong with my solar setup


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I've got 4 X 20.8V solar panels, wired in series/parallel.

On a brilliant, sunny, cloudless day at midday, why am I only getting a voltage of 14.3V?

Batteries (6 X TrojanT-105s wired to give 12V) currently reading 13.2V, so only charging at 4A going from the Tracer, but should the voltage be higher?

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Just now, jenevers said:

I've got 4 X 20.8V solar panels, wired in series/parallel.

On a brilliant, sunny, cloudless day at midday, why am I only getting a voltage of 14.3V?

Batteries (6 X TrojanT-105s wired to give 12V) currently reading 13.2V, so only charging at 4A going from the Tracer, but should the voltage be higher?

If the batteries are full, then the solar will only produce a minimum - 4a would suggest they are full and on float.

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5 minutes ago, jenevers said:

But should the voltage be higher🤔

Not necessarily - a 'tail' voltage will be in the order of 14.2-14.6 volts but once they are 'full' the Float voltage drops down & will be 'in the '13's but the exact number depends on battery type / chemistry and construction. I don't know what Trojans should be.

 

 

Battery charger basics | Chargetek.com

Edited by Alan de Enfield
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1 minute ago, Alan de Enfield said:

Not necessarily - a tail voltage will be in the order of 14.2-14.6 volts buy once they are 'full' the Float voltage drops down & will 'in the '13's but exact number depends on battery type / chemistry and construction. I don't know what Trojans should be.

Agreed as long as he is talking about battery voltage but not if its the panel voltage, with such a low output that shoudl be well over 30 volts. We need to await what voltage he is referring to.

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Just now, Tony Brooks said:

Agreed as long as he is talking about battery voltage but not if its the panel voltage, with such a low output that shoudl be well over 30 volts. We need to await what voltage he is referring to.

 

Very true but I was working on his statement :

 

12 minutes ago, jenevers said:

Batteries (6 X TrojanT-105s wired to give 12V) currently reading 13.2V, so only charging at 4A going from the Tracer,

 

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32 minutes ago, matty40s said:

I would remove the positive panel feed and stick it back in...

And just to be clear, that means disconnect and reconnect the positive wire between the panel and the controller. Do not disconnect the wire between the controller and the battery - if you do the controller may go phut.

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The controller limits the voltage, not the battery. The battery limits the ampage, if it is approaching being fully charged.

 

My controller (tracer) charges at 14.4V provided there is sufficient energy coming in from the panels. When it judges that the batteries are full the controller shifts the voltage down to 13.4V. This is the very purpose of a controller, to reduce the voltage when the battery is full to prevent the batteries bubbling too much, which shortens their life.

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13 minutes ago, The Welsh Cruiser said:

When it judges that the batteries are full the controller shifts the voltage down to 13.4V.

The huge problem being that many controllers’ judgment in this matter is flawed.  

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1 hour ago, Tony Brooks said:

Agreed as long as he is talking about battery voltage but not if its the panel voltage, with such a low output that shoudl be well over 30 volts. We need to await what voltage he is referring to.

Sorry I should have made it clearer. I mean only 14.3V from the panels and 13.2V from the batteries.

Edited by jenevers
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1 hour ago, matty40s said:

I would remove the positive panel feed and stick it back in, just in case your controller has gone to sleep

 

 

Also, where are you taking your voltage reading from, the panel output or battery side??

Thanks, I'll give that a try.

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12 minutes ago, jenevers said:

Sorry I should have made it clearer. I mean only 14.3V from the panels...

Then after you do the switch-off-and-on-again thing as above I suggest you look for a poor connection twixt panels and controller. 

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19 minutes ago, jenevers said:

Sorry I should have made it clearer. I mean only 14.3V from the panels and 13.2V from the batteries.

Is it an MPPT controller or PWM? Sounds like it might be the latter, in which case all panels need to be in parallel.

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15 minutes ago, WotEver said:

Then after you do the switch-off-and-on-again thing as above I suggest you look for a poor connection twixt panels and controller. 

Will do.

8 minutes ago, nicknorman said:

Is it an MPPT controller or PWM? Sounds like it might be the latter, in which case all panels need to be in parallel.

No it's an MPPT.

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5 hours ago, jenevers said:

Sorry I should have made it clearer. I mean only 14.3V from the panels and 13.2V from the batteries.

I couldn’t see having a quick read through the thread, but what is the wattage of your panels?

Edited by Chewbacka
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51 minutes ago, Chewbacka said:

I couldn’t see having a quick read through the thread, but what is the wattage of your panels?

It’s a secret so far ;)

 

But he does have a max of 41.6V. 

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40 minutes ago, Chewbacka said:

But if the panels are small and the batteries flat ...........

Then an MPPT controller should still hold the panel voltage at Vmp which would be around 30 to 35v at a guess, for 2 sets of panels in series.

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1 hour ago, nicknorman said:

Then an MPPT controller should still hold the panel voltage at Vmp which would be around 30 to 35v at a guess, for 2 sets of panels in series.

Yup, agreed.  Hence my suggestion that he checks the panel to controller connections.

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8 hours ago, Chewbacka said:

I couldn’t see having a quick read through the thread, but what is the wattage of your panels?

110watts.

Also the correct voltage of the panels is not 20.8V, it's as below

18.6V (vmp)

22.0V (voc)

Edited by jenevers
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Partial success but the plot thickens!

I actually have 2 identical systems of 4 panels, running side by side, each connected to a tracer controller, feeding the same battery bank. Both were showing low voltage readings. I disconnected the positive leads from the panels to the controllers then reconnected (as per Matty40s). One system registered 32 volts👍. The other registered 22 volts but gradually fell down to 13.7 volts👎.

Wattage. Readings are 25W👍 and 9.9W👎.  (Batteries  12.5v)

Edited by jenevers
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