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12v panels automatically changed to 24v panels

 
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Hello, my name is Tomas.  I'm knew to permies and this is my 1st post ever.
    I live in the Philippines and have a 24v solar system.    I have a 20amp mppt charge controller,  two 100amp hour sealed lead acid batteries and two 100 watt 12v panels.   When I got two more 100 watt 12v panels, I wired then series parallel.   I finished in the dark so I wasn't able to check my voltage.    In the morning,  instead of checking my previous nights work, I just flipped the circuit breaker.  But I accidently forgot to flip the circuit breaker to the batteries first.   After that I wasn't getting a charge indicator light on the controller.   When I went outside to check the problem, all four of my 12v panels were now 24v panels!   Did I damage my diodes?  I went to the city and bought 8 new diodes, 2 for each panel but I haven't installed them yet.  How did this happen?   My entire system is down.  
 
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I seriously doubt it's the diodes. Is there any chance you wired the panels in series by accident?
 
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Hi Tomas, welcome to permies. You most likely did not damage the panels but maybe the controller. Some charge controllers need to have the battery circuit on before receiving charge from the panels or the charging circuit can burn out. Some controllers are not protected from reverse polarity either and again the charge circuit burns out.  Hard to say from a distance. Do you have 2 strings of two panels each? If two panels are hooked up positive to negative in series you should read 24 volts or more on the circuit. Is that the case? Next check polarity of each string using a volt meter. It does happen fairly often...
Cheers,  David
 
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The charge controller may be damaged. But when I checked each panel individually,  they were 24v.  Then I connected two panels together and was getting 48v.   So then I connected three panels in parallel, I couldn't use all 4 panels because I didn't have enough connectors for  my new 24v panels.     I was getting 22v at the charge controller, but the light that indicates I'm receiving power from the panels wasn't on.    It changed  for about a day but the next day it wasn't charging anymore.    The new diodes were 25 cents each, so I will try that 1st.  
 
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Mike Barkley wrote:I seriously doubt it's the diodes. Is there any chance you wired the panels in series by accident?


   Hello Mike, I may have wired them in series but or reversed the polarity.    I can't check it now because I already disconnected all the wires.  But each panel is 24v now.  I checked each panel individually.    When I put two panels in series, 48v.       The diodes are very cheap so I will start with that.    I don't know what else there is inside of the panels that could fail besides the diodes.    
     Thanks for the reply.    
 
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Can't hurt to try the diodes. Make sure to replace them exactly as they came out. They have a plus & a minus side. Backwards could destroy your panels. I'm 99.99999% certain diodes aren't the problem though.

Since even one disconnected panel reads high I'm now thinking the controller is bad & you're reading the unloaded voltage. Mine read about 18 volts unloaded. That seems typical but your panels might be different.  
 
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Mike Barkley wrote:Can't hurt to try the diodes. Make sure to replace them exactly as they came out. They have a plus & a minus side. Backwards could destroy your panels. I'm 99.99999% certain diodes aren't the problem though.

Since even one disconnected panel reads high I'm now thinking the controller is bad & you're reading the unloaded voltage. Mine read about 18 volts unloaded. That seems typical but your panels might be different.  


    Hello Mike,.  Thanks for the information.   The high voltage that I'm reading is 22-23volts on a cloudy day directly from the panels.  Not the charge controller.  Everything is disconnected now.    I'm physically at the panel with the wires directly from the panel into my volt meter.   A 12v panel can't produce that much power.   On the back of the panel it says the maximum it can produce is 18v.    So how is it possible that it's giving me 22v on a semi overcast cloudy day?  I have two volt meters and the electrician neighbor came over also to check it out.   Same result.       All 4 12v panels are individually producing 22+ volts each.   I'm not concerned about the controller now.    I'm just trying to get my panels back to 12 volts.    IT'S A SOLAR MIRACLE!!!
   About the diodes, I plan to solder them in tomorrow.  Thanks for telling me that they have a plus and a minus side.   I didn't know that.  I have a home made tilting frame and I took all the panels off this afternoon.    
    If it's not the diodes, what else is there inside of a solar panel that would change/double the voltage?  I haven't got a clue.     It's just very strange.     Thanks for the info.    Tomas---
 
 
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Hi Tomas;
This is quite the problem!   Your panels have not gone 24 volt or you would be seeing  28-30 volts with an open circuit.
I did not think that the diodes was your problem but now I'm thinking it is a good thing to check.
Maybe you miswired  and shorted them???    It a solar disaster !
Keep us posted.
 
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Yes, please keep us posted. I don't think I've ever heard of a panel doing that. Trying hard to figure out how that is even possible.

Does your meter have a current function? Most do. If it does, put the meter in series with a panel's wires. Does it show any current?



 
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Mike Barkley wrote:Yes, please keep us posted. I don't think I've ever heard of a panel doing that. Trying hard to figure out how that is even possible.

Does your meter have a current function? Most do. If it does, put the meter in series with a panel's wires. Does it show any current?

Hello Mike,
    My friend from the electronic shop came to my house, he soldered in the new diodes.  You were right about the new diodes they had no effect.    He did a few other checks but couldn't find the problem..   I think I ruined all 4 of my solar panels.   The one panel was brand new, never used.    This is truly a disaster!  It's difficult to get solar  panels here,  and I only have a motorcycle.  

IMG_20201007_163238441.jpg
[Thumbnail for IMG_20201007_163238441.jpg]
 
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Tomas Marhold wrote:

Mike Barkley wrote:Yes, please keep us posted. I don't think I've ever heard of a panel doing that. Trying hard to figure out how that is even possible.

Does your meter have a current function? Most do. If it does, put the meter in series with a panel's wires. Does it show any current?

Hello Mike,
    My friend from the electronic shop came to my house, he soldered in the new diodes.  You were right about the new diodes they had no effect.    He did a few other checks but couldn't find the problem..   I think I ruined all 4 of my solar panels.   The one panel was brand new, never used.    This is truly a disaster!  It's difficult to get solar  panels here,  and I only have a motorcycle.   I will check the current in series later today.   I attached a photo of how I got my battery home.   Thanks .

 
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Tomas;
I can see you with solar panel boxes strapped on you like a backpack , riding your scooter back home.
I hope there is a way to repair your panels.
I wonder if a MPPT charge control could make those panels usable ?
 
Mike Barkley
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Nice bike. I'm thinking of trading mine for something more like that. Looks like some really nice batteries too. Which is the only good news because I'm pretty sure something very bad happened to those panels. If you're 100% sure it was wired right the controller is probably trashed too. I still have no explanation on how they could suddenly change to 24 volts. It just doesn't make sense. Seems like a miracle of a bad kind.

 
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Tomas Marhold wrote:
    Hello Mike,.  Thanks for the information.   The high voltage that I'm reading is 22-23volts on a cloudy day directly from the panels.  Not the charge controller.  Everything is disconnected now.    I'm physically at the panel with the wires directly from the panel into my volt meter.   A 12v panel can't produce that much power.   On the back of the panel it says the maximum it can produce is 18v.    So how is it possible that it's giving me 22v on a semi overcast cloudy day?  I have two volt meters and the electrician neighbor came over also to check it out.   Same result.       All 4 12v panels are individually producing 22+ volts each.   I'm not concerned about the controller now.    I'm just trying to get my panels back to 12 volts.    IT'S A SOLAR MIRACLE!!!
   About the diodes, I plan to solder them in tomorrow.  Thanks for telling me that they have a plus and a minus side.   I didn't know that.  I have a home made tilting frame and I took all the panels off this afternoon.    
    If it's not the diodes, what else is there inside of a solar panel that would change/double the voltage?  I haven't got a clue.     It's just very strange.     Thanks for the info.    Tomas---
 



I am in the RP also.  

It is not unusual for a panel to be outside of the listed specs.  Those numbers are measured in a lab under test lighting.  If the energy your receiving is greater than what was in the lab, you could expect it to measure bigger.

I have Jinko 460w panels.  I've measured them putting out greater than 500w on a clear day.

That being said here is what I would do if I were wearing your sineles.

1.)  Find a 150w incandescent light bulb, (or solder up a series string of lower wattage bulbs),  wire on some pig-tails and use it to check the power of each panel.  Put the panel under a load then measure the voltage out and current through the panel.  Measuring a panel's open circuit voltage/current can be misleading.  

Here this will give you an idea of what I am talking about.

https://www.youtube.com/watch?v=JZQEJ33xblE

2.)  I suspect your diodes are good.   But you could get your multimeter and check your diodes.  Most meters have a semi-conductor PN junction test function.  Beeps in one test lead polarity.  No beep when that polarity is reversed.  Double beeps ... shorted diode.  No beeps ... open diode.  

https://www.youtube.com/watch?v=mMXDa5hVzXA

If your meter does not have a diode check function then set it to measure ohms and do the same steps.  Low ohms one way.  High ohms the other.

https://www.youtube.com/watch?v=c5OhQHdCZfA

Most smoked components will be noticeable .  Burned or stinking.

3.) You can test your charge controller by using car/motorcycle batteries.  

You have to have more power coming in than going out.  Most CC manufacturers spec a minimum of 30% more than output battery voltage.  So two panels producing 24vdc under load is going to have a hard time charging a 24vdc battery bank.

Wire three in series for 36vdc.  Wire that cell into the solar panel input breaker on the CC.   Wire two more in series for 24vdc.  Hook that up to the battery out breaker on the charge controller.  

Close the battery side breaker first.  Your cc should boot up.  No blinking lights/led's/lcd's  well its a problem.  If it does boot up ...

Close the "solar input" side breaker.  You should get some indication of current flow from the stack of three batteries into the stack of two.


Hope that helps.

 
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Mark Cunningham wrote:

Tomas Marhold wrote:
    Hello Mike,.  Thanks for the information.   The high voltage that I'm reading is 22-23volts on a cloudy day directly from the panels.  Not the charge controller.  Everything is disconnected now.    I'm physically at the panel with the wires directly from the panel into my volt meter.   A 12v panel can't produce that much power.   On the back of the panel it says the maximum it can produce is 18v.    So how is it possible that it's giving me 22v on a semi overcast cloudy day?  I have two volt meters and the electrician neighbor came over also to check it out.   Same result.       All 4 12v panels are individually producing 22+ volts each.   I'm not concerned about the controller now.    I'm just trying to get my panels back to 12 volts.    IT'S A SOLAR MIRACLE!!!
   About the diodes, I plan to solder them in tomorrow.  Thanks for telling me that they have a plus and a minus side.   I didn't know that.  I have a home made tilting frame and I took all the panels off this afternoon.    
    If it's not the diodes, what else is there inside of a solar panel that would change/double the voltage?  I haven't got a clue.     It's just very strange.     Thanks for the info.    Tomas---
 



I am in the RP also.  

It is not unusual for a panel to be outside of the listed specs.  Those numbers are measured in a lab under test lighting.  If the energy your receiving is greater than what was in the lab, you could expect it to measure bigger.

I have Jinko 460w panels.  I've measured them putting out greater than 500w on a clear day.

That being said here is what I would do if I were wearing your sineles.

1.)  Find a 150w incandescent light bulb, (or solder up a series string of lower wattage bulbs),  wire on some pig-tails and use it to check the power of each panel.  Put the panel under a load then measure the voltage out and current through the panel.  Measuring a panel's open circuit voltage/current can be misleading.  

Here this will give you an idea of what I am talking about.

https://www.youtube.com/watch?v=JZQEJ33xblE

2.)  I suspect your diodes are good.   But you could get your multimeter and check your diodes.  Most meters have a semi-conductor PN junction test function.  Beeps in one test lead polarity.  No beep when that polarity is reversed.  Double beeps ... shorted diode.  No beeps ... open diode.  

https://www.youtube.com/watch?v=mMXDa5hVzXA

If your meter does not have a diode check function then set it to measure ohms and do the same steps.  Low ohms one way.  High ohms the other.

https://www.youtube.com/watch?v=c5OhQHdCZfA

Most smoked components will be noticeable .  Burned or stinking.

3.) You can test your charge controller by using car/motorcycle batteries.  

You have to have more power coming in than going out.  Most CC manufacturers spec a minimum of 30% more than output battery voltage.  So two panels producing 24vdc under load is going to have a hard time charging a 24vdc battery bank.

Wire three in series for 36vdc.  Wire that cell into the solar panel input breaker on the CC.   Wire two more in series for 24vdc.  Hook that up to the battery out breaker on the charge controller.  

Close the battery side breaker first.  Your cc should boot up.  No blinking lights/led's/lcd's  well its a problem.  If it does boot up ...

Close the "solar input" side breaker.  You should get some indication of current flow from the stack of three batteries into the stack of two.


Hope that helps.

Hello Mark,  Thanks for all of the information.  I think you know a lot about electricity and solar.  Yesterday I put one panel in the sun and hooked up the multi meter.    22.4 volts and around 2.4 - 3.04 Amps. But the Amps kept fluctuating.       Upon further inspection the silver ribbons in the panels look damaged at the intersections.   I attached a photo.     Surprisingly, one panel is working but damaged.    I switched my batteries back to 12v and using the one panel to charge them but it's not working so good.    I got a battery charger today and using it now to keep the batteries fresh.     But they sat at 12.4 for a weeks.   I will check out your function test on YouTube.     I ordered a soldering iron from Shopee but it didn't arrive yet.    I borrowed one from my friend but it has no power it's useless.
   I'm in Nueva Ecija, Palayan city, Luzon.   Small Town.    
    Thanks.   Ignat.     T---

IMG_20210323_124007233.jpg
[Thumbnail for IMG_20210323_124007233.jpg]
 
Mark Cunningham
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Tomas Marhold wrote:

Hello Mark,  Thanks for all of the information.  I think you know a lot about electricity and solar.  Yesterday I put one panel in the sun and hooked up the multi meter.    22.4 volts and around 2.4 - 3.04 Amps. But the Amps kept fluctuating.       Upon further inspection the silver ribbons in the panels look damaged at the intersections.   I attached a photo.     Surprisingly, one panel is working but damaged.    I switched my batteries back to 12v and using the one panel to charge them but it's not working so good.    I got a battery charger today and using it now to keep the batteries fresh.     But they sat at 12.4 for a weeks.   I will check out your function test on YouTube.     I ordered a soldering iron from Shopee but it didn't arrive yet.    I borrowed one from my friend but it has no power it's useless.
   I'm in Nueva Ecija, Palayan city, Luzon.   Small Town.    
    Thanks.   Ignat.     T---




Ok let's do a bit of math.  22.4vdc * 2.4a = 53.76 watts.  I seem to remember that those were 100w panels.  To be honest that sounds about right to me.

The specs that you were sold are not the specs that you can expect the panel to produce in real life.  Look at your spec sheet, (may have to download it from the mfg),  Most will have a "STC" and NMOC rating.  Standard test conditions, (the best they can get in a lab setting).  Normal mode of ..... whatever.  That is usually 70%->90% of STC.  Estimated real life.   You were advertised STC specs.

My Jinko's STC is 460w.  The NMOC is something like 360w if memory serves.  I've measured them producing 500+ watts.

So sticking a meter on a panel in an open circuit normal environment is good for basic  Pass/Fail tests.   Not so good for actual real world performance testing.

What is the Model and Mfg for your panels and charge controller?   I'll look them up and maybe we can sort this out.




 
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I would agree an open voltage of 22 or 23 volts is not unusual on a 12 volt panel. Please dont tear it open yet. I would try the 3 panel experiment on the mppt charger first. 1.5 times battery voltage for an mppt string is very common. A 24 volt string open circuit voltage up to 50 volts will not power my mppt charge controller.  I use an outback 60 amps charger. Do you have a make and model for the charger?
 
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