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Old 08-31-2018, 07:28 PM   #21
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Originally Posted by TitanMike View Post
What is the "No Load" voltage output of your panels? From what I've been reading/learning is that some panels deliver more than enough voltage on their own to satisfy the needs of an MPPT controller. They could be lower output of 17- 18 volts or well into the 30 volt range. The small panels I have have an open circuit voltage of 20-22 volts.

If yours are the higher voltage panels then it may be better to stay parallel due to the fixed rooftop panels being more vulnerable to shading.

As it was pointed out earlier, I can move my panels around to avoid shading.
Output voltage at the installation shop was 22V max.
I got home in the dark and left for work next day, in the dark. When I got home had nothing from solar as they had left the main solar switch OFF.
Checking today after work.
Panel mounts under construction that will allow up to 60Deg of elevation and full 360 rotation to always point north and 45Deg elevation.
Will look further into volts etc over the weekend.
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Old 08-31-2018, 07:32 PM   #22
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Originally Posted by ScottBrownstein View Post
"12 volt panels" have an open circuit voltage of 19 or higher. Their maximum power point voltage is closer to 16 or 17 volts. MPPT controllers want some voltage to work with and many will handle up to 100 volts or so. This allows series panels with smaller wire at lower currents. Power is voltage multiplied by current and big systems often use voltages even above 100 volts to allow much smaller conductors. MPPT controllers are more efficient but really only for systems of 500 watts or more. Big residential panels have voltages significantly higher than 20 volts and require MPPT.

Why is MPPT only more efficient with 500 watts or more?
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Old 08-31-2018, 07:37 PM   #23
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Because you need a significantly higher voltage for MPPT to do its stuff. A couple of panels really isn't enough and...MPPT is not 100% efficient and has some significant controller losses. Series panels suffer from more serious shading effects as well. Basically you can't build a 1000 watt system without series panels and higher voltage than 17 or so.

In effect, MPPT is more efficient as the voltage rises...
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Old 09-01-2018, 04:11 AM   #24
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Originally Posted by TitanMike View Post
Correct me if I'm wrong but don't most panels use a combination of series and parallel connections within themselves. Some groups of cells wired in series and then groups wired in parallel. Doesn't this help overcome some of the shading effect when wired in series.

Also, don't panels incorporate bypass circuitry that prevents the "series wired christmas tree light effect"?

I've watched the demo's on YouTube and see how some power is lost but it was only "some", not "all".
Each solar cell is about .6 volts. Most 12v panels have 33-36 cells in series. My 'slim' 100 watt panels have 33 cell. (3 x 11 cells) Each are arranged in parallel to minimize shading. The parallel panels voltage levels are high enough to have at least a 10% higher battery charge amperage with the MPPT. My only concern is the voltage drop between the solar panels & the MPPT. I plan to use Power Distribution Blocks to combine my 10AWG cables pairs from the solar array to 6AWG at my new Victron 100/50 MPPT.

My Renogy 100 Watt 12 Volt Monocrystalline Solar Panel (Slim Design) Specifications:
Optimum Operating Voltage (Vmp): 16V
Open-Circuit Voltage (Voc): 20V

Below is screenshots of my MPPT solar charge controller:
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Old 09-05-2018, 05:02 PM   #25
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Originally Posted by rk06382 View Post
Each solar cell is about .6 volts. Most 12v panels have 33-36 cells in series. My 'slim' 100 watt panels have 33 cell. (3 x 11 cells) Each are arranged in parallel to minimize shading. The parallel panels voltage levels are high enough to have at least a 10% higher battery charge amperage with the MPPT. My only concern is the voltage drop between the solar panels & the MPPT. I plan to use Power Distribution Blocks to combine my 10AWG cables pairs from the solar array to 6AWG at my new Victron 100/50 MPPT.

My Renogy 100 Watt 12 Volt Monocrystalline Solar Panel (Slim Design) Specifications:
Optimum Operating Voltage (Vmp): 16V
Open-Circuit Voltage (Voc): 20V

Below is screenshots of my MPPT solar charge controller:
Attachment 185061Attachment 185062Attachment 185063Attachment 185064
I have my Victron SmartSolar MPPT 100/50 installed.
1Click image for larger version

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1>Early Morning Sun.
2>Mid-day Sun for Alaska.
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Old 09-05-2018, 05:06 PM   #26
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Originally Posted by rk06382 View Post
I have my Victron SmartSolar MPPT 100/50 installed.
What is interesting is that you are getting a 12.5% increase in current with your parallel setup. With my series setup, I get close to 25% increase after taking into account the doubling of the voltage. Exact same Victron controller. I do believe my solar panel voltage is much higher which may have something to do with it.

EDIT: I think that is what we are seeing here. Lower voltage from your panels compared to mine. If I had low voltage panels like that, I would definitely be doing a series connection.
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Old 09-05-2018, 05:31 PM   #27
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Originally Posted by TitanMike View Post
Forgot to mention:
Another reason I am using the Victron MPPT controller is I decided I wanted a controller mounted near my batteries. Since the reference voltage will be coming from the batteries over approximately 3' of #4 awg wire,...
Do you use a Victron battery monitor like a BMV-712 by chance? If so, you can network them if you are using the SmartSolar version of the solar controller and the battery monitor sends the solar controller the reference voltage.
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Old 09-05-2018, 06:09 PM   #28
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Originally Posted by babock View Post
What is interesting is that you are getting a 12.5% increase in current with your parallel setup. With my series setup, I get close to 25% increase after taking into account the doubling of the voltage. Exact same Victron controller. I do believe my solar panel voltage is much higher which may have something to do with it.

EDIT: I think that is what we are seeing here. Lower voltage from your panels compared to mine. If I had low voltage panels like that, I would definitely be doing a series connection.
Quote:
Originally Posted by babock View Post
Do you use a Victron battery monitor like a BMV-712 by chance? If so, you can network them if you are using the SmartSolar version of the solar controller and the battery monitor sends the solar controller the reference voltage.
Yes, I have the BMV-712 networked with the MPPT.

The think if I had 273 watt at double the voltage it would half the amperage but still be 273 watts.

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Post a screenshot of your MPPT if I am missing something.
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Old 09-05-2018, 06:30 PM   #29
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The think if I had 273 watt at double the voltage it would half the amperage but still be 273 watts

Post a screenshot of your MPPT if I am missing something.
I agree.

When I first posted I didn't see that your panel voltage was so much lower than mine.

I do know that when the sun starts rising, my panel voltage, because they are in series, starts the controller earlier than if they were in parallel. When I installed my brothers. MPPT 150/50 we were able to get way better overall watt hours in series overall during the day than what we were able to get in parallel.

I do see that with your shading issues with your AC, you are probably better off with them in parallel. I know some people with your configuration use taller mounts to reduce the shading of AC units. Just something to maybe keep in mind down the road.
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Old 09-05-2018, 07:26 PM   #30
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Do you use a Victron battery monitor like a BMV-712 by chance? If so, you can network them if you are using the SmartSolar version of the solar controller and the battery monitor sends the solar controller the reference voltage.
Yes, also get battery temp from the monitor so charge rate is adjusted accordingly.
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