PV panels/charge controller issues

I have four 200 watt panels hooked in series.

My charge controller shows a PV input of 84ish volts and 200 watts in almost full sun.

If I hooked just two of the panels in series, I get 40is volts and 177 watts.

I should have sets of 2 in series, connected in parallel which should give me 40ish volts and 354vwatts in the same sun, right?

That is correct based on the info you recorded and published.

Connected in series increases voltage and allows for smaller gauge wires.
Connected in parallel increases the amperage/wattage and requires larger gauge wires.

Parallel is also better if you may experience some shade.

I like the combo, it is what we do. Same set up with QTY - 4 200 watt panels connected series parallel.

What's the power rating of your controller? Or a make and model.

I've tried editing my original post twice now and failed. Likely due to a really crappy connection on our end.

The controller is a Powmr HHJ-60A mppt.

Josh Hoffman wrote:That is correct based on the info you recorded and published.

Connected in series increases voltage and allows for smaller gauge wires.
Connected in parallel increases the amperage/wattage and requires larger gauge wires.

That was why I originally did all 4 together. We used it like that for a year now and I just wasn't really paying attention. Now I'm a little annoyed that we have likely been wasting half the power we collected lol

Josh Hoffman wrote:

Parallel is also better if you may experience some shade.

I like the combo, it is what we do. Same set up with QTY - 4 200 watt panels connected series parallel.

Just ordered some Y connectors and will switch it when they come in.

Crinstam Camp wrote:Now I'm a little annoyed that we have likely been wasting half the power we collected lol

There are a lot of factors and you may not have been wasting anything depending on the setup, unless you experience some shade.

The MPPT controller is a revolutionary piece of equipment. Sometimes higher voltage is better for MPPT because you can buy smaller gauge wire and lower rated components.

For our setup, we would not want to increase the amperage because we'd need to increase wire size and the controller itself. It is sized correctly as is.

I would just crunch the numbers to make sure your current wire gauge and controller maximum rating meet what the sun will give you in parallel-series combo.

Josh Hoffman wrote:

.....The MPPT controller is a revolutionary piece of equipment. Sometimes higher voltage is better for MPPT because you can buy smaller gauge wire and lower rated components.

For our setup, we would not want to increase the amperage because we'd need to increase wire size and the controller itself. It is sized correctly as is.

I would just crunch the numbers to make sure your current wire gauge and controller maximum rating meet what the sun will give you in parallel-series combo.

I enjoy messing around with electric golf carts and UTVs and have been slowly coming up to speed with the particulars of solar charging.  Is the reduced cable diameter also true for the battery connectors if one is modifying a vehicle from 36V to 48V or higher?  The 36V carts use pretty beefy cables between the batteries.  Can this gauge be reduced for the between-battery connections in a 48V vehicle?  Thanks!

John Weiland wrote:I enjoy messing around with electric golf carts and UTVs and have been slowly coming up to speed with the particulars of solar charging.  Is the reduced cable diameter also true for the battery connectors if one is modifying a vehicle from 36V to 48V or higher?  The 36V carts use pretty beefy cables between the batteries.  Can this gauge be reduced for the between-battery connections in a 48V vehicle?  Thanks!

You would have to figure out all of your variables if you wanted to try to size the correct wire. It would be a little tricky for DC motors (when you provide less or more voltage than the motor is rated for on the tag) because there is a relationship to the voltage and winding size/speed etc.

I doubt the change in wire size would be very significant in the 36 or 48 volt scenario. Maybe 1 size up or down. Applying 48 volts to a 36 volt motor winding will result in increased speeds but potential to overheat the motor windings would exist. Applying 36 volts to a 48 volt motor would result in reduced speeds.

The reason it is significant in the post here (solar) is because of the somewhat fixed nature of the solar panels output and the cumulative effect. Whereas a golf cart or utv has a fixed number of motors.

So taking your 2 panels in series as the baseline.

177/2=88.5 watts per panel. 88.5/195=0.454, so your installed efficiency is 45% of the max of the panels.

For the 2s2p setup I would agree that you should get 4*88.5=354 watts.

But your results for 4 in series is weird. I would have expected you to be getting 354w at about 81V.

84v per 4 panels is 21V per panel which is nudging towards the open circuit voltage of 24.5V. At 200w you were only getting 2.38A from the panels rather than about 4.5A.


I would be really curious to see if you did get 350w when wired for 2series 2 parallel. I think something weird is going on with the controller limiting the power.

This is all assuming that there enough load on the controller to let the panels make their full power.

James Alun wrote:So taking your 2 panels in series as the baseline.

177/2=88.5 watts per panel. 88.5/195=0.454, so your installed efficiency is 45% of the max of the panels.

For the 2s2p setup I would agree that you should get 4*88.5=354 watts.

But your results for 4 in series is weird. I would have expected you to be getting 354w at about 81V.

84v per 4 panels is 21V per panel which is nudging towards the open circuit voltage of 24.5V. At 200w you were only getting 2.38A from the panels rather than about 4.5A.


I would be really curious to see if you did get 350w when wired for 2series 2 parallel. I think something weird is going on with the controller limiting the power.

This is all assuming that there enough load on the controller to let the panels make their full power.

James, the 2 panels in series would result in a reduction of voltage, not wattage, if you removed a panel.

It looks like the first line of your post is taking the 2 panels in series and dividing the watts by 2 and leaving the voltage the same rather than dividing the voltage by 2 and leaving the watts the same.

The series wiring results in increased voltage with same wattage.

The parallel wiring results in increased wattage with same voltage.

Josh are you sure about that?

As I understand it.
Series the voltage adds and the current stays the same.
Parallel the voltage stays the same and the current adds.

Twice as many panels should all ways give twice the power regardless of configuration.

James Alun wrote:Josh are you sure about that?

As I understand it.
Series the voltage adds and the current stays the same.
Parallel the voltage stays the same and the current adds.

Twice as many panels should all ways give twice the power regardless of configuration.

Yes I am saying the same thing. I think the mistake is in the first line of your reply

James Alun wrote: So taking your 2 panels in series as the baseline.

177/2=88.5 watts per panel. 88.5/195=0.454, so your installed efficiency is 45% of the max of the panels.

You should divide the voltage in 2 on the baseline series configuration but you are dividing the wattage in 2.

So then, based on this baseline:

Crinstam Camp wrote:I have four 200 watt panels hooked in series.

If I hooked just two of the panels in series, I get 40is volts and 177 watts.

Each individual panel provides 20 volts and 177 watts.

4 panels in series would be:
80 volts and 8.85 amps

4 panels in parallel would be:
20 volts and 35.4 amps

4 panels in series-parallel would be:
40 volts and 17.1 amps


***Edited to show values in amps, not watts***

Dividing the wattage in 2 is the same as dividing the voltage in 2, if current is the same.
P=IV

4V*3A=12W  2V*6A=12W
2V *3A=6W   4V*1.5A=6W

There's no reason for the current supplied by each individual panel to drop when placed in parallel.

"4 panels in series would be:
80 volts and 177 watts

4 panels in parallel would be:
20 volts and 708 watts

4 panels in series-parallel would be:
40 volts and 354 watts"

I would say that the total going into the controller

4 panels in series would be:
4*20=80 volts,1*4.5= 4.5A, 360W

4 panels in parallel would be:
1*20=20 volts, 4*4.5=18A, 360watts

4 panels in series-parallel would be:
2*20=40 volts, 2*4.5=9A, 360watts

James Alun wrote:
I would say that the total going into the controller

4 panels in series would be:
4*20=80 volts,1*4.5= 4.5A, 360W

4 panels in parallel would be:
1*20=20 volts, 4*4.5=18A, 360watts

4 panels in series-parallel would be:
2*20=40 volts, 2*4.5=9A, 360watts

It looks like you are assigning 4.5 amps to the panels. I believe it should be 8.85 amps

We know a single panel produces 20 volts and 177 watts in full sun (approximately). 177 watts / 20 volts = 8.85 amps per panel. (20V 8.85A)

4 panels in series would be:
4*20=80 volts,1*8.85=8.85 amps (80V 8.85A)

4 panels in parallel would be:
1*20=20 volts, 4*8.85=35.4 amps (20V 35.4A)

4 panels in series-parallel would be:
2*20=40 volts, 2*8.85 =17.1 amps (40V 17.7A)

James Alun wrote:Dividing the wattage in 2 is the same as dividing the voltage in 2, if current is the same.
P=IV

The original post gave 2 panels in series. The voltage would need to be divided in two.

Josh Hoffman wrote:

It looks like you are assigning 4.5 amps to the panels.

Yep, I am

Josh Hoffman wrote:

This will vary depending on the number of panels and if they are wired in series or parallel.

The array current will change, the individual currents will not. There is no reason for the current being produced by an individual panel to drop unless the controller cannot handle the full array current.


From Footprinthero's series parallel page.

James Alun wrote:

Josh Hoffman wrote:

It looks like you are assigning 4.5 amps to the panels.

Yep, I am

How did you come to this number?

I think this is the sticking point. In the illustration you posted and in both my posts and your posts, we agree that series wiring increases voltage but current stays the same.

If we take the original post information of 2 panels in series producing 40 volts and 177 watts, we would need to halve the voltage, not the amperage to get the value of one panel.

Therefore 1 panel produces 20 volts and 177 watts. Solving for single panel amperage would be 177 watts divided by 20 volts equals 8.85 amps. We can then plug the 8.85 amps into the 3 different configurations.

Josh Hoffman wrote:
4 panels in series would be:
4*20=80 volts,1*8.85=8.85 amps (80V 8.85A)

4 panels in parallel would be:
1*20=20 volts, 4*8.85=35.4 amps (20V 35.4A)

4 panels in series-parallel would be:
2*20=40 volts, 2*8.85 =17.1 amps (40V 17.7A)

Using these figures of 177 watts/20volts/8.85amps lines up with the label posted above buy the original poster. The label is with the panel functioning at optimal performance. The original post recordings are a little less, which is to be expected.

This was why I assumed it was the controller limiting the power. These are screenshots from the manual.

I believe it is saying if it's over 60 volts, the controller will limit it.

Tomorrow I'll hook the individual panels up and get readings from each seperately and post them.

Crinstam Camp wrote:
That was why I originally did all 4 together. We used it like that for a year now and I just wasn't really paying attention. Now I'm a little annoyed that we have likely been wasting half the power we collected lol

Crinstam Camp wrote:This was why I assumed it was the controller limiting the power. These are screenshots from the manual.

I believe it is saying if it's over 60 volts, the controller will limit it.

Tomorrow I'll hook the individual panels up and get readings from each seperately and post them.

When I look up your model, I get the specs below on the website. You would be right at the volt max at 4 panels in series with 80 volts.

In a 12 volt system, you need ~14 volts to charge.

In your situation, you have 80 volts and 8.85 amps. The MPPT would drop the voltage to the 14 volts needed and convert the excess voltage into increased amperage. The PWM would not convert the excess rather it would just be turning off and on rapidly to charge the batteries with what you provide to it. The MPPT utilizes the available resources much better then the PWM when charging.

There are pros and cons to all the different scenarios. Feeding the MPPT the high voltage/low amps rather than low voltage/high amps, series/parallel/combo wiring etc.

We arrived at having 300AH lithium batteries, 800 watts of solar wired in series/parallel and a MPPT controller. We have been using them for 4.5 years and have not changed a thing.

Josh Hoffman wrote:

James Alun wrote:

Josh Hoffman wrote:

It looks like you are assigning 4.5 amps to the panels.

Yep, I am

How did you come to this number?

I think this is the sticking point. In the illustration you posted and in both my posts and your posts, we agree that series wiring increases voltage but current stays the same.

Yes but you haven't been keeping the current the same, you've been keeping the power the same.

Josh Hoffman wrote:
If we take the original post information of 2 panels in series producing 40 volts and 177 watts, we would need to halve the voltage, not the amperage to get the value of one panel.

Yes, we halve the voltage and keep amperage the same.
Halving the voltage, keeping the amperage the same halves the power.

Josh Hoffman wrote:
Therefore 1 panel produces 20 volts and 177 watts.

No, 1 panel produces 20V but not 177 watts.

2 panels produce 40 volts multiplied by N amps = 177 (in series)
1 panel produces 20 volts multiplied by N amps = 177/2

N did not change. N will only change if the amount of light hitting the panel changes.

I x V = P
I x (V/2)=P/2

Crinstam Camp wrote:This was why I assumed it was the controller limiting the power. These are screenshots from the manual.

I believe it is saying if it's over 60 volts, the controller will limit it.

Tomorrow I'll hook the individual panels up and get readings from each seperately and post them.

That makes a whole heap of sense.

Switching to series-parallel will bring your voltage down below the protection voltage and then you can get full power from your panels.

Josh Hoffman wrote:The MPPT would drop the voltage to the 14 volts needed and convert the excess voltage into increased amperage.

Except it's not doing that. When I split it into two sets of 2, both produce 177W, as 1 set of 4 it's only producing 200ish.

Crinstam Camp wrote:

Josh Hoffman wrote:The MPPT would drop the voltage to the 14 volts needed and convert the excess voltage into increased amperage.

Except it's not doing that. When I split it into two sets of 2, both produce 177W, as 1 set of 4 it's only producing 200ish.

When you hook 4 panels in series  you say you get "84ish volts and 200 watts in almost full sun"

When you hook 2 panels in series you say you get "40ish volts and 177 watts"

Have you tried the series parallel with the 4 panels yet in similar sun?

Crinstam Camp wrote:I have four 200 watt panels hooked in series.

My charge controller shows a PV input of 84ish volts and 200 watts in almost full sun.

If I hooked just two of the panels in series, I get 40is volts and 177 watts.

I should have sets of 2 in series, connected in parallel which should give me 40ish volts and 354vwatts in the same sun, right?

Lots of good points raised. What I want to know is the size of your battery bank and how old it is. The charge controller can be trying to restrict what your batteries get depending on how big the bank is. You get best utilization of solar on lead batteries at about C10 or 10 percent of rated capacity of the batteries. So 800 watts of solar would need 8kW of battery storage to use the full 800 watts effectively. A good test is to hook up a load equal to the maximum output of your solar on a sunny day and run it. I test with a 1200 watt space heater. With that running see how much your panels put out. If you get near full output (say 80 percent) from the panels with a big load on the system the panels are good, the batteries are the weak link.
CHeers,  David

James Alun wrote:Yes but you haven't been keeping the current the same, you've been keeping the power the same.

Okay, I see what you are saying with me keeping the power constant and not the current in my posts like I should be.

If his panel were producing 20 volts and 177 watts, it would be 91% efficient. That would be more inline with the tag on the panel.

But the 2 together are only producing the 177 watts.

Josh Hoffman wrote:

James Alun wrote:Yes but you haven't been keeping the current the same, you've been keeping the power the same.

Okay, I see what you are saying with me keeping the power constant and not the current in my posts like I should be.

If his panel were producing 20 volts and 177 watts, it would be 91% efficient. That would be more inline with the tag on the panel.

But the 2 together are only producing the 177 watts.

Exactly!
And that's where my figure of 45% came from.

So now there are 2 broad possibilities, well actually 3.
Either the panels aren't generating the power properly eg dirty, misaligned, very old etc.
Or the power is being lost somewhere eg very long cables, cables too small.

Or possibly measurement error eg measuring at the wrong time of day, measurement averaged instead of instantaneous, etc.

Or the bits that David is talking about.

James Alun wrote:

Josh Hoffman wrote:

James Alun wrote:Yes but you haven't been keeping the current the same, you've been keeping the power the same.

Okay, I see what you are saying with me keeping the power constant and not the current in my posts like I should be.

If his panel were producing 20 volts and 177 watts, it would be 91% efficient. That would be more inline with the tag on the panel.

But the 2 together are only producing the 177 watts.

So now there are 2 broad possibilities, well actually 3.
Either the panels aren't generating the power properly eg dirty, misaligned, very old etc.
Or the power is being lost somewhere eg very long cables, cables too small.

Or possibly measurement error eg measuring at the wrong time of day, measurement averaged instead of instantaneous, etc.

No, actually none of those are a possibility, because when I hook just 2 panels in series, I was getting 177 watts, when I change it to 4, with all those things you mention, remaining the same, I get 200 watts.

We aren't talking theory here, this is what's actually happening.

Crinstam Camp wrote:

James Alun wrote:

Josh Hoffman wrote:

James Alun wrote:Yes but you haven't been keeping the current the same, you've been keeping the power the same.

Okay, I see what you are saying with me keeping the power constant and not the current in my posts like I should be.

If his panel were producing 20 volts and 177 watts, it would be 91% efficient. That would be more inline with the tag on the panel.

But the 2 together are only producing the 177 watts.

So now there are 2 broad possibilities, well actually 3.
Either the panels aren't generating the power properly eg dirty, misaligned, very old etc.
Or the power is being lost somewhere eg very long cables, cables too small.

Or possibly measurement error eg measuring at the wrong time of day, measurement averaged instead of instantaneous, etc.

No, actually none of those are a possibility, because when I hook just 2 panels in series, I was getting 177 watts, when I change it to 4, with all those things you mention, remaining the same, I get 200 watts.

We aren't talking theory here, this is what's actually happening.

sounds like your wiring is not the issue. What battery bank size are you using?

David Baillie wrote:What battery bank size are you using?

6 x 12.8v 100Ahr LiFeP04 in parallel.

Crinstam Camp wrote:I believe it is saying if it's over 60 volts, the controller will limit it.

That 60 volt limit is on output voltage not the input.

Input voltage range is 20-80v. While 84v is above that so maybe they are putting a hard limit for 200w to prevent overheating.

Crinstam Camp wrote:

James Alun wrote:

Josh Hoffman wrote:

James Alun wrote:Yes but you haven't been keeping the current the same, you've been keeping the power the same.

Okay, I see what you are saying with me keeping the power constant and not the current in my posts like I should be.

If his panel were producing 20 volts and 177 watts, it would be 91% efficient. That would be more inline with the tag on the panel.

But the 2 together are only producing the 177 watts.

So now there are 2 broad possibilities, well actually 3.
Either the panels aren't generating the power properly eg dirty, misaligned, very old etc.
Or the power is being lost somewhere eg very long cables, cables too small.

Or possibly measurement error eg measuring at the wrong time of day, measurement averaged instead of instantaneous, etc.

No, actually none of those are a possibility,

He is talking about your other problem, why those two panels are only producing at 45% efficiency?

Crinstam Camp wrote:

David Baillie wrote:What battery bank size are you using?

6 x 12.8v 100Ahr LiFeP04 in parallel.

Thanks, so that rules that out.

Alex Ronan wrote:

Crinstam Camp wrote:I believe it is saying if it's over 60 volts, the controller will limit it.

That 60 volt limit is on output voltage not the input.

Input voltage range is 20-80v. While 84v is above that so maybe they are putting a hard limit for 200w to prevent overheating.

Crinstam Camp wrote:

James Alun wrote:

Josh Hoffman wrote:

James Alun wrote:Yes but you haven't been keeping the current the same, you've been keeping the power the same.

Okay, I see what you are saying with me keeping the power constant and not the current in my posts like I should be.

If his panel were producing 20 volts and 177 watts, it would be 91% efficient. That would be more inline with the tag on the panel.

But the 2 together are only producing the 177 watts.

So now there are 2 broad possibilities, well actually 3.
Either the panels aren't generating the power properly eg dirty, misaligned, very old etc.
Or the power is being lost somewhere eg very long cables, cables too small.

Or possibly measurement error eg measuring at the wrong time of day, measurement averaged instead of instantaneous, etc.

No, actually none of those are a possibility,

He is talking about your other problem, why those two panels are only producing at 45% efficiency?

Chances are that your controller is pooched then. Do you have a clamp on amp meter? Make sure the amps going into the battery match what your controller is saying. If I was trouble shooting this one I would start by unhooking each panel, shorting each panel's cables and checking the amp reading of each. Rebuild your string when you know each panel is performing well independently. That controller is supposed to take a single string of all four so don't waste time trying to make it work with two strings. If your output does not match the sum of your individual panels results the controller is shot. It is far more likely that an entry level controller is not working than 4 solar panels malfunctioning.  

Alex Ronan wrote:

Crinstam Camp wrote:I believe it is saying if it's over 60 volts, the controller will limit it.

That 60 volt limit is on output voltage not the input.

Input voltage range is 20-80v. While 84v is above that so maybe they are putting a hard limit for 200w to prevent overheating.

Crinstam Camp wrote:

James Alun wrote:

Josh Hoffman wrote:

James Alun wrote:Yes but you haven't been keeping the current the same, you've been keeping the power the same.

Okay, I see what you are saying with me keeping the power constant and not the current in my posts like I should be.

If his panel were producing 20 volts and 177 watts, it would be 91% efficient. That would be more inline with the tag on the panel.

But the 2 together are only producing the 177 watts.

So now there are 2 broad possibilities, well actually 3.
Either the panels aren't generating the power properly eg dirty, misaligned, very old etc.
Or the power is being lost somewhere eg very long cables, cables too small.

Or possibly measurement error eg measuring at the wrong time of day, measurement averaged instead of instantaneous, etc.

No, actually none of those are a possibility,

He is talking about your other problem, why those two panels are only producing at 45% efficiency?

Clouds arent cooperating today, but there was enough sun to watch as the volts went over 80, the wattage went down. I watched it bounce from the high 70s to low 80s multiple times and saw it repeated.

Edited to add: it doesn't limit the wattage in that manner anyway, today when it was 79ish it was about 267 watts, as it went above 80v the wattage started to drop. If we had more sun today I'm pretty sure it will keep dropping the wattage as it goes higher but it didn't even hit 81 today.

As for the efficiency of the panels, it was never the point of my post, if it had been I would have pointed out it was smokey and hazy in the air at the time.

Crinstam Camp wrote:

No, actually none of those are a possibility, because when I hook just 2 panels in series, I was getting 177 watts, when I change it to 4, with all those things you mention, remaining the same, I get 200 watts.

We aren't talking theory here, this is what's actually happening.

Sorry Crinstam, I was throwing out my thoughts on the list of possibilities that assumed that all of the equipment was functioning properly.

Since I haven't seen it mentioned yet, and since I think everyone has by now figured out that panels in series add voltage and in parallel add current, what I will point out is that yes, higher voltage is always better for lower current and therefore smaller wires, BUT every charge controller has an absolute maximum input voltage limit. Exceed that, and you'll damage the charge controller (MPPT or regular). And to decide what maximum voltage the controller will see, worst-case, use the open-circuit output voltage numbers off the solar panels, not the voltage measured in normal operation when they're being loaded down somewhat. For example, if the Voc ("Voltage, open-circuit") on a panel is 22V, and you have 4 in series, your charge controller must be able to withstand an 88V input without damage.

David Baillie wrote:Chances are that your controller is pooched then.

I think the controller is working as designed. If the controller was bad then it would be noticed when 2 panels are connected also. An even number of 200w output makes me think it is doing what it was designed to (a safety feature). Broken things usually have random results.

it was 79ish it was about 267 watts, as it went above 80v the wattage started to drop.

That is was I would expect from a safety power limit (hard limit was probably the wrong terminology). Once the controller goes over the max input voltage it starts lowering the amps until it reaches the power limit (which appears to be 200w).

Alex Ronan wrote:
I think the controller is working as designed. If the controller was bad then it would be noticed when 2 panels are connected also.

I think you're correct in this, which is wjy I pointed out the comparison between two and four.

We've used this system like this since last spring. I just didn't pay enough attention when we upgraded from our old panels.

I fully expect once we get the Ys in that we'll see full power output when appropriate.

It should also mean we could add two more panels and switch it to a 3x2 setup?

Crinstam Camp wrote:It should also mean we could add two more panels and switch it to a 3x2 setup?

For voltage, yes, you can have 3 in series.

But the max wattage for a 12v system with that controller is 720w, you will be WAY over wattage connecting 6 (3 series x 2 parallel) 195w panels. Even 4 panels (2x2) is pushing the limit if start getting closer to ideal conditions.