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Hannes Bester

Solar configuration

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Hi all hope you all well...... 

I would like to find out if it's possible to have different sizes panels in a solar array? 

I currently have 2 x 285w panels and would like to add 4 x 370w panels. 

Would this be possible? 

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17 minutes ago, Hannes Bester said:

Would this be possible? 

Hi Hannes. 

You need to match the voltage of the existing string when installing new panels. If you cant, in short, you will degrade that new panels to the same about the same size as the old ones. You will have a lot less issues if you stick to panels as close as possible to your existing panels. 

Look at the VOC rating of the exiting 2 panels, I assume they are connected in Series, then try to match that rating with the panels you add.

There is long explanations around this, but you will end up paying for 370 watts and only getting out 285 watt. 

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14 hours ago, Hannes Bester said:

I would like to find out if it's possible to have different sizes panels in a solar array?

Yes it is but as @Jaco de Jongh stated; don't go that way!

On what device are the 2 x 285 panels connected?

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1 hour ago, RikH said:

Yes it is but as @Jaco de Jongh stated; don't go that way!

On what device are the 2 x 285 panels connected?

They are currently connected to a expert 3kva plus model so I wanted to replace it with 4 x 370w panels but then I had the idea of an external mppt to connect them all but if it's going to be a pro I'm going to add the 4 x 370w panels to the inverter and the 2 x 285w panels on mppt straight to the batteries. 

I thought the inverter could only handle 600w which explains the 2 x 285w panels then I realized it's a plus model 😶

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The sticker on the right side of the inverter will tell you what you can connect to it and how. Putting the other 2 panels on a separate charge controller is the only thing you can do when you want everything as efficient as possible.

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Ok, so I’m in the pre-noob stage (joined the forum today). But it occurs to me that there might be a way...

What if you connect two strings of panels in parallel, with 1x 285w and 2x 370w in each string? If the total voltage on each string doesn’t exceed the MPPT controller rating, wouldn’t that work?

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Hi Everyone Thanks for all the good tips. Just added solar to my Mecer 5000 watt inverter. 12 x CNBM 6P-330 330W POLYCRYSTALLINE SILICON SOLAR PANE 4 strings x 3 panels each into a solar db board with fuses. I am getting 1.2 kw on the inverter under pv input. Is this right or did I connect something wrong as I thought I would get much more. Thanks Wayne

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17 minutes ago, WayneSi said:

I am getting 1.2 kw on the inverter under pv input. Is this right or did I connect something wrong as I thought I would get much more. Thanks Wayne

Hi Wayne, The PV production will start very low as the sun rises in the morning, reaching its peak at around noon and then decreasing again as the sun moves over and sets giving you a nice almost halve round curve if you have enough loads. 

The other factor to keep in mind, the panels can only generate power if there is a demand for it, so lets say at noon you only have a 500 wh load switched on, your panels will only generate 500 watt. 

So to know if your panels are connected correctly, wait for noon and switch a nice big load on, preferably a load 80-90% of your array size, and then gradually add a few small loads to see what your system can produce. Depending on your mounting direction and angle, you can expect 3200wh -  3600wh on a nice sunny day. If you get a lot less than that, you can start checking your wiring, fuses ext

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5 hours ago, moron51 said:

What if you connect two strings of panels in parallel, with 1x 285w and 2x 370w in each string? If the total voltage on each string doesn’t exceed the MPPT controller rating, wouldn’t that work?

Without looking at the exact specs for your panels, the theory remains the same. 

The 285 watt panel in each string will effectively limit the 370 watt panels to 285 watt panels as well. In theory you will have 855 wh per string. 

Strangely enough, we had another member a week or 2 ago that also asked about adding 4 x 370 watt new panels to 2 x 285 watt existing panels.... 

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15 hours ago, Jaco de Jongh said:

Hi Wayne, The PV production will start very low as the sun rises in the morning, reaching its peak at around noon and then decreasing again as the sun moves over and sets giving you a nice almost halve round curve if you have enough loads. 

The other factor to keep in mind, the panels can only generate power if there is a demand for it, so lets say at noon you only have a 500 wh load switched on, your panels will only generate 500 watt. 

So to know if your panels are connected correctly, wait for noon and switch a nice big load on, preferably a load 80-90% of your array size, and then gradually add a few small loads to see what your system can produce. Depending on your mounting direction and angle, you can expect 3200wh -  3600wh on a nice sunny day. If you get a lot less than that, you can start checking your wiring, fuses ext

Hi Jaco Thanks for responding.

So its starts at 300 to 400 watt and builds till 1.2 kw then goes down like you said. My load is always more than 1.2 kw and when the pool pump goes on it goes to 2.2 kw. and then they use the microwave it goes to 3kw.  So the load always more than what is produced. That's why I want at least 3kw of solar to cover it as when the utility kicks in when the sun goes down it always has to charge the batterie because it used quiet a lot of battery during the day. And when Eskom starts its load shedding I am going to be in trouble for the evening load shedding when the batteries are low.

I connected up 3 panels together in series and used 6 mil solar flex wiring to bring the positive and negative down to the fuse box. I hope its not the fuses. When I use the meter. The 3 panels comes to 270 on the meter . 2nd and 3rd and 4th string says 270. When I Check the mains on the DB board it also says 270. I thought it would add it all together. 

Thanks for your help so far.

Wayne

 

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38 minutes ago, WayneSi said:

I hope its not the fuses.

What is the rating of the fuses? 

Do you know how to test continuity? Chose the Ohm setting on your meter, remove a fuse and test for continuity over the fuse. It should be lower than 1 ohm. 

38 minutes ago, WayneSi said:

thought it would add it all together. 

 

Please post the specks of your panels. 270 volts for a 3 panel string does not seem right. And please also post a picture of the sticker on the side of your inverter. Depending on the model, 270 volt seems to high.

Something in this value (270) volt and 12 panels in 3s4p does not make sense. 

EDIT: A little sketch of how you connected everything will also help. and maybe a picture of the combiner box?

Ah wait, I think I see whats happening here. Here is the specks. 

Panels.png.0a83fa6f1c7cadc8abec30691700167b.png

47 volt open circuit x 6 = 282volt... and 6 x 330 watt is 1980 wh minus losses should give around 1580 wh... 

I think you have six panels in series and the other six is not connected to the inverter.. 

 

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18 hours ago, Jaco de Jongh said:

What is the rating of the fuses? 

Do you know how to test continuity? Chose the Ohm setting on your meter, remove a fuse and test for continuity over the fuse. It should be lower than 1 ohm. 

Please post the specks of your panels. 270 volts for a 3 panel string does not seem right. And please also post a picture of the sticker on the side of your inverter. Depending on the model, 270 volt seems to high.

Something in this value (270) volt and 12 panels in 3s4p does not make sense. 

EDIT: A little sketch of how you connected everything will also help. and maybe a picture of the combiner box?

Ah wait, I think I see whats happening here. Here is the specks. 

Panels.png.0a83fa6f1c7cadc8abec30691700167b.png

47 volt open circuit x 6 = 282volt... and 6 x 330 watt is 1980 wh minus losses should give around 1580 wh... 

I think you have six panels in series and the other six is not connected to the inverter.. 

 

Hi There

Ok I have 5 kw RCT Inverter with 4 x 200ah Gel Batteries . 12 x 330 watt panels.

Here is the Inverter pics and Solar Panel specs + Plan. I also used the laptop to see specs of software inside the Inverter via usb. Also I think I had it on the wrong setting on  the tester. Check in Pic if its in the right place please.125.4  is on all 4 strings and on the mains. 

But when I switch the mains on the inverter clicks to PV the Tester drops to 53.7. Let me know if you need anything else or any other pics.

  • STC Power Rating 330W
  • PTC Power Rating 302.47W 1
  • STC Power per unit of area 170.1W/m2 (15.8W/ft2)
  • Peak Efficiency 17.01%
  • Power Tolerances 0%/+3%
  • Number of Cells 72
  • Nominal Voltage not applicable
  • Imp 8.85A
  • Vmp 37.3V
  • Isc 9.26A
  • Voc 45.9V
  • NOCT 45°C
  • Temp. Coefficient of Isc 0.05%/K
  • Temp. Coefficient of Power -0.41%/K
  • Temp. Coefficient of Voltage -0.142V/K
  • Series Fuse Rating 15A
  • Maximum System Voltage 1000V

 

Thanks in Advance Wayne

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20200510_152112_resized.jpg

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18 minutes ago, WayneSi said:

Let me know if you need anything else or any other pics.

Thank you, from what I see here everything looks fine. When the sun is out tomorrow, please open all the fuses and then measure the voltage athe the bottom of the fuses, string by string to ensure all 4 strings are producing power. 

21 minutes ago, WayneSi said:

But when I switch the mains on the inverter clicks to PV the Tester drops to 53.7.

This should not happen with all 4 strings connected. 

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12 minutes ago, Jaco de Jongh said:

Thank you, from what I see here everything looks fine. When the sun is out tomorrow, please open all the fuses and then measure the voltage athe the bottom of the fuses, string by string to ensure all 4 strings are producing power. 

This should not happen with all 4 strings connected. 

Hi There

That's Exactly what I did on the pics above . Opened up all the fuses and did pv+1 and pv-1 then the rest till pv 4 separately at the bottom. And all came to the same 125.4. then I pushed all the fuses up again and checked the mains ,and it had 125.4.   Must it drop down like that when the inverter kicks into pv mode to 53.7

Can it be the Inverter that is Faulty.

 

Must I change Bulk charging voltage CD to 57.7

Float charging voltage 54.4

Max charging time CV 60 min

Battery cut off Voltage 49.v

 

I see you recommended that to someone else.

 

Thanks Wayne

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3 minutes ago, WayneSi said:

Must it drop down like that when the inverter kicks into pv mode to 53.7

Nope, its should drop to about 110-115 volts, maybe a bit lower with very heavy loads. 

6 minutes ago, WayneSi said:

Must I change Bulk charging voltage CD to 57.7

Float charging voltage 54.4

Max charging time CV 60 min

Battery cut off Voltage 49.v

Not sure about your battery specs.. have to check it,.

Did you check the continuity of your fuses?

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On 2020/05/08 at 5:25 PM, moron51 said:

with 1x 285w and 2x 370w in each string - wouldn’t that work?

Nope. In a string you should only use the same panels and with the same orientation. Otherwise you will fall back to the level of the weakest panel or worse.

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On 2020/05/08 at 11:14 PM, Jaco de Jongh said:

Strangely enough, we had another member a week or 2 ago that also asked about adding 4 x 370 watt new panels to 2 x 285 watt existing panels.... 

Haha yes that's what I thought. I don't want to disclose his name but it started with a H and ended with annes Bester. First post in this topic.

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3 hours ago, WayneSi said:

Must it drop down like that when the inverter kicks into pv mode to 53.7

Can it be the Inverter that is Faulty.

Hi Wayne, I think that voltage drop to 53.7V is normal and I also think your inverter is doing what it is supposed to do. My reason is looking at your laptop data, if you have an actual load of 1189W as seen on your laptop and your PV is showing 554W you should actually add the two together = 1743W (Total actual generated.)

Than your discharge current was 14A at the time.

Take the 1743W/14A= 124.5V this is spot on as you measured with the multi-meter. you can also look on the inverter display and use the Amps reading and PV (Volts) and PV (Watts) and use the same above little formula it should be spot on every time. If you have no load “on”when doing these checks than the PV (Watt) reading will seem to be higher if the battery requires it for charging, even than the formula should work. Just my 2cents😁

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2 hours ago, Gerrie said:

My reason is looking at your laptop data, if you have an actual load of 1189W as seen on your laptop and your PV is showing 554W you should actually add the two together = 1743W (Total actual generated.)

Gerrie, i dont know what to say right now, but lets look at this again....

The load is 1189 watts, right? on the AC side, that will be 1189 / 236.1 VAC = 5.03 amps. 

So the 14 amps Discharge is definitely not the AC amps, correct? If it was the load should have been 236.1V x 14A = 4627.6 Watts.

The fact that its called Discharge amps is because it is the amps drawn from the batteries at that moment. so 50.4 Volts DC x 14 amps = 705.6 watts from batteries, plus 554 watts from pv = 1259.6 Watts (Load) 

The question is, why would the 12 x 330w (3960whp) panels only give 554wh when the load is only 1200?? watts, and take the rest from the batteries. 

2 hours ago, Gerrie said:

I think that voltage drop to 53.7V is normal and I also think your inverter is doing what it is supposed to do.

And no, this is not normal for a 1218w load to pull down the voltage of a 3960 wh array from 125 to 53 volts, unless this test was done early morning or late afternoon..

 

EDIT: I see this test was done 15H19, so a volt drop is normal in this case. 

 

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4 hours ago, Gerrie said:

Hi Wayne, I think that voltage drop to 53.7V is normal

Sorry, I disagree. It's a huge drop from 125 V, and it's just a few volts over the battery voltage. It's as if the MPPT is stuck on solid, not switching. As if it's a PWM model (but it doesn't appear to be an MPPT model by the label).

Quote

if you have an actual load of 1189W as seen on your laptop and your PV is showing 554W you should actually add the two together = 1743W (Total actual generated.)

Sorry to disagree again. It's showing zero charge current, and 14 A discharge current. So the battery is providing some 14 x 50.4 = 706 W.

Than your discharge current was 14A at the time.

Quote

Take the 1743W/14A= 124.5V this is spot on as you measured with the multi-meter.

You're dividing the total load by just the current provided by the battery; the result is meaningless. The fact that it's nearly Voc for the panels is merely coincidence.

Here's my calculation.

PV power + battery power = output power + losses

554 + 706 = 1189 + losses

losses = 1260 = 1189 = 71 W. We expect a constant loss of a little under 50 W, so the rest is switching loss.The real battery current could be as high as 14.9x A (it gets truncated in factory firmware), so that probably explains the unexpectedly low loss.

@WayneSi, it does look like your MPPT may be faulty, or somehow they bolted a PWM solar controller inside a box with an MPPT sticker. But actually, a PWM controller would have well less than a volt drop; this sounds more like the MPPT is doing the best it can with very poor PV input (bucking very slightly, only about 2 V).

But the other possibility, which seems much more likely, is that you have a high resistance connection somewhere in the PV input, causing the PV voltage and hence power to collapse. Perhaps a non-contact thermometer can locate the problem; it could be getting quite hot dropping decent voltage at 10 A (= 554 W / 53.7 V). Check for voltage drops along the PV input wiring. If it's not after your junction box, then it's weird because it would have to be common to all three PV strings. I've not heard of a bad batch of panels, but that is an outside chance as well.

When all is working well, in full sun I'd expect the panel voltage to drop to some 90-100 V, but no lower than that.

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5 hours ago, Jaco de Jongh said:

And no, this is not normal for a 1218w load to pull down the voltage of a 3960 wh array from 125 to 53 volts,

Oh!! Jaco / Coulomb great!! 2 against 1 not fair,  I can’t argue further😬😁 🤣

I’m wrong!! I apologize, but I can’t understand as I have been through a exercise about 4weeks back on my own clone and I know my PV voltage is different to Wayne’s. Mine is only PV min= 36VDC and V max=105VDC. (My aray with inverter switched off is normally about 88V this only two panel series x 3p)so when I start loads and pulling from PV the voltage normally sit closely to the 54VDC range

I also got Voltages from PV even as low as 53V when dc current where 30A with Watts at 1680W. Now maybe my inverter can also be faulty that I’m not aware of but it basically run off-grid everyday since these checks and I did not experience any issues. When my batteries were  “I think” fully charged with no load and inverter just sitting idling even the fan switches off, the Voltage where 56V with 2A charging and 189Watt. When start taking load again it would drop again and deliver the Watts to loads in conjunction with battery bank. I don’t make use of a laptop and software but measured directly on pv terminals with a tong tester and multimeter. What am I not seeing?  

I still have my scribbled notes with these low voltages.

 

 

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