Solar array voltage and battery charging

[acecard]

Hi guys,

I'm on a journey to understand the intricacies of my system!

I have a 3kW array capable of about 320VOC, connected to an AIO 5kW unit. I'm in the UK, and my panels are mounted flat, so I am of course not seeing very high array voltages much at the moment. I've been watching the data output from my unit for a while now, and my array seems to sit at 120V a lot. Yet, at this voltage I don't seem to get any charging current to the battery. Is this normal?? My battery is only at about 50% SOC so surely I should be getting at least some charging if my array is producing voltage?

 

[timselectric]

Check the voltage range for the PV input on the AIO.
It's possible that you are too low at 120v.

 

[acecard]

Check the voltage range for the PV input on the AIO.
It's possible that you are too low at 120v.

Thanks, so I looked in the manual and found something called "start-up" voltage and also "voltage range". The latter says 120-450V and the former says 150V. So it would seem this inverter needs a minimum of 150V in order to begin it's function, although I'm a little confused as to why the manual says the voltage range is from 120 if the charge function doesn't even kick in til 150! Is there a way to modify the system to be able to make use of the sub-150V area of the array, as on low light days, it does seem to however around this point for a lot of the day, and seems like a big waste!

 

[timselectric]

Thanks, so I looked in the manual and found something called "start-up" voltage and also "voltage range". The latter says 120-450V and the former says 150V. So it would seem this inverter needs a minimum of 150V in order to begin it's function, although I'm a little confused as to why the manual says the voltage range is from 120 if the charge function doesn't even kick in til 150! Is there a way to modify the system to be able to make use of the sub-150V area of the array, as on low light days, it does seem to however around this point for a lot of the day, and seems like a big waste!

It takes 150v to wake it up. But only 120v to keep it awake.

 

[TomC4306]

Once you get the load of the mppt turned on, the voltage won't wander around as much with varying conditions.

And actually, my pv voltage is lower in bright sun. The mppt's job is to maximize current. It does that by minimizing voltage required for itself. Today was a perfect example. Crystal clear bright Sun. three panels in a string 82 volts. cloudy day 90 volts.

 

[acecard]

Thanks for the responses guys. I've watched it for a while this morning and on a number of occasions the voltage went over 120V, even to 180V and one point and still no charging current to the battery. Does it need to be over the minimum voltage for a certain amount of time before beginning to charge? Sorry if these questions seem basic, I'm just really struggling to understand how this thing works!! Another thing is that I read that the unit circuitry is the same for charging and inverting, meaning it can't do both at the same time. If that is the case, surely that isn't efficient as I'm inverting pretty much all of the time!

As you may have seen from previous posts of mine, I have been believing that my solar isn't performing right, even accounting for the fact that I'm in the UK in winter. I go days sometimes with literally zero solar production, and with a 3kW array, I really thought I would be getting at least something!

 

[timselectric]

Does it need to be over the minimum voltage for a certain amount of time before beginning to charge?

I have seen it take a couple of minutes, to get going.

Another thing is that I read that the unit circuitry is the same for charging and inverting, meaning it can't do both at the same time.

It can do both at the same time.

As you may have seen from previous posts of mine, I have been believing that my solar isn't performing right, even accounting for the fact that I'm in the UK in winter. I go days sometimes with literally zero solar production, and with a 3kW array, I really thought I would be getting at least something!

I agree that you should be able to get something on most days.

 

[TomC4306]

On is the mppt waking up.
It then loads the panels, drawing the voltage back down.
That secondary ramp up is the mppt finding the power point.
Then making work (Watts).

 

[TomC4306]

Perspective.

 

[TomC4306]

Question...
Is there absolutely no way that you can raise one edge of these panels up? If you are in the UK I don't know 52° north latitude and you have these panels laying flat on the ground they're not going to make much power at all. You would do better to stand them up vertically.

 

[740GLE]

Question...
Is there absolutely no way that you can raise one edge of these panels up? If you are in the UK I don't know 52° north latitude and you have these panels laying flat on the ground they're not going to make much power at all. You would do better to stand them up vertically.

Summer time won’t be bad, winter time horrendous.

 

[timselectric]

View attachment 121369On is the mppt waking up.
It then loads the panels, drawing the voltage back down.
That secondary ramp up is the mppt finding the power point.
Then making work (Watts).

That time frame is way too long.
It should happen in a minute or two, not over an hour and 20 minutes.
But the description is accurate.

 

[timselectric]

When the voltage gets above 150v. It starts to put a load on the panels. This load pulls the voltage down. If it pulls it down below 120v, it stops and repeats when the voltage goes back above 150v. This continues until it's able to pull a load and stay above 120v.
The MPPT increases the load (amps) and monitors the output (Watts). When more load pulls the voltage down enough to actually decrease output, it holds there.
As the sun rises, the voltage will increase. The MPPT increases the load again, and monitors the output.
Everything works in reverse when sunlight decreases.
It adjusts and checks continuously throughout the day. Keeping the output at it maximum.

 

[TomC4306]

That time frame is way too long.
It should happen in a minute or two, not over an hour and 20 minutes.
But the description is accurate.

Had to wait until this morning to see what actual time the sun clears my horizon. 7:30 is when the first rays of sunshine actually begin hitting the panels. Everything prior to that is over the horizon dawn.
This is my first ever solar system so I don't have any prior reference for the little details like mppt time to find. I'm happy with how it's operating. Making 2kw+ from 9am past 3. Peak on this array is currently about 3.5k. Provided clear and sunny. 6 strings.
2nd array voltage is wacky early because the shadow is cast from very close to the array and sweeps across the 2 strings.

 

[Hardergamer1]

I'm in the UK too, but at the southern tip at Lat50.350, and I'm making voc by 8am with MPPT bringing it down to MPV, even when it's raining it stays around MPV just the amps drop.
But the difference is my panels are angled at 55* which I change to 63* soon.
I deleted part of my text somehow lol, As Tom said above can you lift the high end of your panels up? As even lifting them 4-5 inches will help bring the voc up, have a play with this app to see how much extra power you may gain. https://re.jrc.ec.europa.eu/pvg_tools/en/

 

[acecard]

Question...
Is there absolutely no way that you can raise one edge of these panels up? If you are in the UK I don't know 52° north latitude and you have these panels laying flat on the ground they're not going to make much power at all. You would do better to stand them up vertically.

Sadly I can't as they are laying on top of my RV. I did toy with the idea of making a tilting mechanism, but this was going to add to much weight and height.

 

[acecard]

I'm in the UK too, but at the southern tip at Lat50.350, and I'm making voc by 8am with MPPT bringing it down to MPV, even when it's raining it stays around MPV just the amps drop.
But the difference is my panels are angled at 55* which I change to 63* soon.
I deleted part of my text somehow lol, As Tom said above can you lift the high end of your panels up? As even lifting them 4-5 inches will help bring the voc up, have a play with this app to see how much extra power you may gain. https://re.jrc.ec.europa.eu/pvg_tools/en/

Thanks, this app is similar to the globalsolaratlas website I've been using, both suggest I should be getting much more than I am, even with my panels laying flat.