Good day

i have two 400 w solar panels in very hot sun and clear sky..

now im not familiar in understanding this program so well.

but what i want to know on this picture with 2 x 400 w panels.... where on the picture does it possibly say im getting around 800 watts..?

 i see the 437 watts being used by the computer running but pv input power reads 471.

 so do i add these together to get the whole sum or is one of the panels not working so well?

 

thanks

The panels are producing the same amount as your load, so 437W of load + 34W of inverter consumption = 471W. Your batteries are fully charged so there is nothing for the panels to do. Add more load...... 

Typed all this out and got beaten to the enter key. But anyway, what he said in other words...

Best guess is that your panels (under control of the MPPT) are producing only enough to supply your actual demand, and not any excess energy that would cause some overheating and damage to the system. Out of the total 471W power being generated, 437W is being output to your computer (actual active loads), and the rest is probably self-consumption by the inverter and some heat dissipation in the wiring, etc. The battery is full at 100% capacity, so no energy could/should be going towards charging the battery.

Other issues surrounding the 800W: The nameplate 800W capacity is a theoretical maximum measured under ideal laboratory conditions, ie low temperature, with light shining 90 degrees onto the panel. In reality the maximum power you can harvest at any given time will be lower than the 800W depending on factors like the position of the sun, the time of day, the day in the season, angle of your roof, the weather, temperature of the panels, efficiency losses in the inverter, etc.

And then, just say that right at this moment, in this environment, when the panels can produce for argument's sake 700W maximum, then it will still only produce as much as the load that you put onto it. You might have headroom to add an extra smallish load onto it like a 200W television, and make the panels work a little harder. But then if you exceed the momentary production capacity of the system, like by turning on a 1000W toaster, you'll start to drain power from the battery to supplement the power demand.

The MPPT is limiting the power since the batteries are full and the load is low. Bear in mind you will only get 800W out of the panels at midday, if they are in an optimal orientation. 

ok....im really trying to understand this...

 

when i loaded a second computer on see how the out put and input pv changed...but then it switched over automatically to eskom as the two panels  couldnt give enough power it seems.

This one is harder to explain - let me give it a stab:

Your load is 1000W. It indicates that the load is 25% of max - so you probably have a 4000w inverter.  Your batteries are full. Let's say you can get 700W from solar.

If your inverter has a proper reading of the State of Charge (SOC) of the battery, it would supply the load from the battery AND solar input, and not switch back to the grid.

However, it is clear that the inverter has switched to the grid - it is only using 168W from solar to top up the battery at 2 Amps.

What probably happened is the following: The load you are drawing is 1000W.  The inverter tried to supply the load, drawing from the battery and solar.  There are two things that will get the inverter to switch back to grid:

1) Under load, the battery voltage drops (to say 49V) due to internal resistance, or the battery pack being a bit small (and solar too) - AND the inverter does not read the SOC from a proper battery Management System (BMS).  When this happens, the inverter determines the battery SOC from the battery voltage, which has dropped to a level that would indicate the battery is flat. This can happen very quickly.  The voltage level is not a reliable method of determining SOC. Shazam - the inverter switches back to the grid. Solution: get a BMS or a BMV700 that will give the inverter a proper SOC.  This will allow the inverter to continue working even at lower battery voltages - it will essentially ignore the battery voltage and rely on the proper SOC. The specific bms to get would depend on your inverter model and battery.  Some combinations are incompatible and will not be able to read the SOC.

2) Depending on the inverter, there could be a software maximum current setting for the battery - to protect the battery - which will cause the same result.  If this is the case, investigate what the max charging or discharging limit for you battery should be.  Exceeding this will shorten your battery life.

However, knowing you should be able to get 700W from solar, this means that somehow your inverter could not even draw 300W from the batteries - this is worrying.  I would get a clever person to investigate the system - it should perform better.

Another solution would be to add more solar panels - but first get the battery working properly.

I you want better answers, you will have to list your full system component list here - specific inverter, batteries, BMS, everything.

So the true answer to all of this is ?????

regarding the panel watts not really showing 700-800 watts

On 2019/09/10 at 7:24 PM, Dennis said:

So the true answer to all of this is ?????

regarding the panel watts not really showing 700-800 watts

you will possibly never see 800W because of losses and conditions, but you will see as close to it as the panels can provide PROVIDED you have enough load that does not exceed the PV. You dont mention what inverter you have, but I am guessing a regular axpert, that inverter cannot mix sources, and once you exceed the load that the panels can provide you will switch back to grid.

eg:

- PV potential is 700W and you are drawing 300W, the PV wattage will show 300W. 

- PV potential is 700W and you are drawing 900W, the PV wattage will show 0 (unless the battery is charging for example - but none of the available 700W will go to load)

 

what is your setting? SUB?

 

On 2019/09/10 at 5:09 PM, Ironman said:

This one is harder to explain - let me give it a stab:

Your load is 1000W. It indicates that the load is 25% of max - so you probably have a 4000w inverter.  Your batteries are full. Let's say you can get 700W from solar.

If your inverter has a proper reading of the State of Charge (SOC) of the battery, it would supply the load from the battery AND solar input, and not switch back to the grid.

However, it is clear that the inverter has switched to the grid - it is only using 168W from solar to top up the battery at 2 Amps.

What probably happened is the following: The load you are drawing is 1000W.  The inverter tried to supply the load, drawing from the battery and solar.  There are two things that will get the inverter to switch back to grid:

1) Under load, the battery voltage drops (to say 49V) due to internal resistance, or the battery pack being a bit small (and solar too) - AND the inverter does not read the SOC from a proper battery Management System (BMS).  When this happens, the inverter determines the battery SOC from the battery voltage, which has dropped to a level that would indicate the battery is flat. This can happen very quickly.  The voltage level is not a reliable method of determining SOC. Shazam - the inverter switches back to the grid. Solution: get a BMS or a BMV700 that will give the inverter a proper SOC.  This will allow the inverter to continue working even at lower battery voltages - it will essentially ignore the battery voltage and rely on the proper SOC. The specific bms to get would depend on your inverter model and battery.  Some combinations are incompatible and will not be able to read the SOC.

2) Depending on the inverter, there could be a software maximum current setting for the battery - to protect the battery - which will cause the same result.  If this is the case, investigate what the max charging or discharging limit for you battery should be.  Exceeding this will shorten your battery life.

However, knowing you should be able to get 700W from solar, this means that somehow your inverter could not even draw 300W from the batteries - this is worrying.  I would get a clever person to investigate the system - it should perform better.

Another solution would be to add more solar panels - but first get the battery working properly.

I you want better answers, you will have to list your full system component list here - specific inverter, batteries, BMS, everything.

imo his system is doing exactly what it was designed to do (unless I am mistaken on what he has), he must have his setting on SUB and the unit cannot mix, so once pv potential is reached it will switch. I "think" if he had it on SBU he would see what he expects, but obviously that means that he will run his batteries, and depending on his setup that could leave him in the dark.

8 hours ago, Dennis said:

regarding the panel watts not really showing 700-800 watts

At this time of year, I'd expect only 600 W max from nominally 800 W panels; perhaps edging towards 650 W towards the end of spring. You can see the full 800 W or perhaps a bit more when the panels are new, they face the sun at a good angle, it's summer, near the middle of the day, there are clouds, and for thirty seconds or so after the cloud suddenly passes you'll see that power level. That's the reality of panel production, and it's the reason for NOCT (Normal Operating Cell Temperature) ratings.

[ Edit: speaking of which, I just saw a peak of 6062 W of PV power from my two 3000 W SCCs, when my panels total 5650 W nominal. So I guess it can happen in spring, too. ]

You will only even see this 600-650 W when the Solar Charge Controller has somewhere to put it, either charging a not-nearly-full battery, or (partially) supplying loads.

Patched firmware (see this post for what patched firmware, if any, you can run) does a better job (via KettleKomp™) than factory firmware, as far as staying in battery mode (and several other areas, particularly battery charging).

Edited September 11, 20196 yr by Coulomb

You'll seldom see 800 watts from those panels. I have a theoretical 3900 W of solar power on my roof, but I never see it, the sun would have to be shining optimally on all panels at the same time. That would mean, amongst other things,  that the angle of the panels has to be optimal. They should be at a steeper angle in the winter than in the summer, which means that most of the year they are at a less than optimal angle.

In my case there is another factor. The panels are split into two arrays - one facing east, one facing north (both with an -ish suffix). So the chance of all panels working optimally at the same time is about zero

 

Is it possible that your inverter is set to maintain the batteries at 100% so that you have maximum battery life in case of an outage?

My system can be set to run that way. In that mode it just keeps the batteries provided at 100% and the solar makes no contribution to servicing the load. I run it in hybrid mode which balances the various resources, using solar first, battery second and mains as a last resort.

Wow..

Thanks guys for all the info from you  that messaged here.

Appreciated