6 minutes ago, Prinolan said:

Morning

I have read through this forum and am having a similar challenge with my PV

I have a 5kw Must Hybrid Inverter with built in MPPT. 9 x 365w panels (connected 3 in series x 3 rows). And 4 x 200ah gel batteries.

My system works on a load matching basis for the solar during the day and at night draws from the batteries but keeps the batteries at 50.0V in case of load shedding.

Normally the PV voltage ramps up to around 120V and charge power ranges anywhere from 500w to 3,500w depending on the load needs.

It’s been working well since i installed (a month ago) however from 2 days ago i noticed on the monitoring system that (while the sun is out and sky clear) the PV voltage spikes to higher levels ie around 125V or above and the charge power drops to around 150w and the charger current drops to 2.9-3.1a - this happens for a period ranging from 15mins to 1.5hrs - the first day was 1.5hrs at one go (from 7.15-8.45am) and then 10-15min periods three times after and then day 2 15mins and yesterday 15mins both around 2pm

Any ideas?

should i change my bulk and float rates for my battery

it only started behaving like this after the heavy rain and storms on the weekend but i cant imagine thats changed anything as it works like normal for most of the day except for these short periods when i see the dips

 

PV table1.bmp 1.52 MB · 0 downloads PV graph1.bmp 863.68 kB · 0 downloads

Hi,

The 145v MPPT starts to derate the PV from 125v.

You will have to rewire you panels to have 2 panels in series in order to drop the voltage.

1 hour ago, Bloubul7 said:

Hi,

The 145v MPPT starts to derate the PV from 125v.

You will have to rewire you panels to have 2 panels in series in order to drop the voltage.

ok but normally it runs at around 119-122V

but with this change in charge current where it drops to ~3A and 150w the voltage is spiking to the 125 or higher

sometimes that drop to 3A occurs even when PV voltage is below 120V - and other times even when Voltage is higher than 125V the charge power is still good ie about 600w etc

initially had only 8 panels and voltage was sitting at 80-90 but sometimes dropped to 60 which meant the MPPT switched off. Added a 9th panel to then connect 3 x 3 and voltage picked up to ~120V (normally hovers around 119) and system seems to operate well at that rate

dont understand why all of a sudden its giving this issue when it worked perfectly for the first month

could it be a battery issue?

1 hour ago, Prinolan said:

ok but normally it runs at around 119-122V

but with this change in charge current where it drops to ~3A and 150w the voltage is spiking to the 125 or higher

sometimes that drop to 3A occurs even when PV voltage is below 120V - and other times even when Voltage is higher than 125V the charge power is still good ie about 600w etc

initially had only 8 panels and voltage was sitting at 80-90 but sometimes dropped to 60 which meant the MPPT switched off. Added a 9th panel to then connect 3 x 3 and voltage picked up to ~120V (normally hovers around 119) and system seems to operate well at that rate

dont understand why all of a sudden its giving this issue when it worked perfectly for the first month

could it be a battery issue?

I would not go back to having two panels in series. That was my main problem, because when the voltage dropped too low, the MPPT would switch off. I have three panels in series and four strings in parallel and have not had an issue for a long time. I however use Pylontech batteries.

1 hour ago, Pipes said:

I would not go back to having two panels in series. That was my main problem, because when the voltage dropped too low, the MPPT would switch off. I have three panels in series and four strings in parallel and have not had an issue for a long time. I however use Pylontech batteries.

i have seen on this forum discussion about others having similar issues of PV drop and most attribute it to an issue with the MPPT which or battery which is the issue but was just trying to get an opinion as most are using Lithium batteries whereas i have gel which may be very different in the way they charge etc. so looking for best solution re bulk and floating charge rates

currently my bulk is at 56.4v and floating at 54v - its default on my inverter

should i reduce this perhaps and if so are there any risks in doing that?

really i am trying to figure out why the charge power is dropping to 150w and 3A if the sun is out and the batteries arent close to float - is the mppt faulty

bear in mind its very adhoc and doesnt happen frequently at all - maybe 1 x 15min period during the day - although on the first day it was frequent and it goes back to normal again without me having to do anything but still a concern for me

18 hours ago, Prinolan said:

I have a 5kw Must Hybrid Inverter with built in MPPT. 9 x 365w panels (connected 3 in series x 3 rows).

It’s been working well since i installed (a month ago) however from 2 days ago i noticed on the monitoring system that (while the sun is out and sky clear) the PV voltage spikes to higher levels ie around 125V or above and the charge power drops to around 150w and the charger current drops to 2.9-3.1a - this happens for a period ranging from 15mins to 1.5hrs -

My strong guess (it's impossible to be sure that's happening inside a clone) is that the SCC is overheating due to the high panel voltage. It should not (if it copied the Axpert behaviour exactly) be limiting power until the panel voltage (as read by the inverter) reaches 130 V. You could possibly convince yourself that it's temperature related by temporarily adding extra cooling, and noting whether the charge current increases.

As I now say in my signature, 3S of 72-cell panels is always trouble.

On 2020/02/27 at 11:24 PM, KobusC said:

My panels are also wired 3 per series, so I assume my PV voltage is fine.

Only if they are 60-cell panels.

Edit: can you monitor your inverter temperature?

Edited November 6, 20205 yr by Coulomb

15 hours ago, Prinolan said:

whereas i have gel which may be very different in the way they charge etc. so looking for best solution re bulk and floating charge rates

currently my bulk is at 56.4v and floating at 54v - its default on my inverter

should i reduce this perhaps and if so are there any risks in doing that?

Those settings are standard for a gel battery. Yes, there is a risk when reducing the voltages that the battery will not charge fully, and that will reduce life.

However, reducing the absorb/bulk voltage about half a volt in summer is a good idea. I would not change the float voltage; it's a little on the low side already, and the temperature coefficient for the float voltage is usually less than that for the absorb voltage.

4 hours ago, Coulomb said:

My strong guess (it's impossible to be sure that's happening inside a clone) is that the SCC is overheating due to the high panel voltage. It should not (if it copied the Axpert behaviour exactly) be limiting power until the panel voltage (as read by the inverter) reaches 130 V. You could possibly convince yourself that it's temperature related by temporarily adding extra cooling, and noting whether the charge current increases.

As I now say in my signature, 3S of 72-cell panels is always trouble.

how would i add extra cooling?

and no dont think there is a way to monitor the temp of the inverter

i hear the fans going when the sun is out

i can go listen to it when it gets very hot

but its amazing that it does it so infrequently

 

22 hours ago, Pipes said:

I would not go back to having two panels in series. That was my main problem, because when the voltage dropped too low, the MPPT would switch off. I have three panels in series and four strings in parallel and have not had an issue for a long time. I however use Pylontech batteries.

I agree with this, provided they are 60-cell panels.

1 hour ago, Prinolan said:

how would i add extra cooling?

and no dont think there is a way to monitor the temp of the inverter

i hear the fans going when the sun is out

i can go listen to it when it gets very hot

but its amazing that it does it so infrequently

 

If you use the ICC software, you can monitor the inverter temperature. See below 

Just an update on my experience with this... the issue has not yet reoccurred for me, but the temperatures have been fairly moderate of late with a fair bit of rain & cool weather. And the inverter does not seem to have been working as hard. It could well be a temperature thing as @Coulomb suggests - seems most likely to me. 

I am, however, probably going to ditch my "Axpert" (I reckon it's a clone, grrr...) in favour of a Sunsynk fairly soon, so not sure I will be able to contribute experience on this point for too much longer.

Incidentally, it seems to me that the Axpert's MPPT range of 60-115dv (145vdc max) is a bit limiting, and ends up being a bit restrictive in terms of PV array arrangement & wiring. Feels like the inverters with higher MPPT voltages going up to around 450-500vdc are just much more convenient, flexible. Fewer strings, lower current & thinner cables, etc. And in some cases dual MPPTs, like on the Sunsynk.

5 hours ago, Prinolan said:

how would i add extra cooling?

I imagined holding a house fan under the fans at the bottom of the inverter. Blowing the same way as the internal fans, of course. [ Edit: Possibly with the cable cover off, presuming that there is such a thing. ]

Quote

and no dont think there is a way to monitor the temp of the inverter

With Axperts, I believe that you can read the maximum temperature on the provided Watchpower application. Probably with other monitoring software as well.

Edited November 6, 20205 yr by Coulomb

Hi

I see no-one has come up with a solution to the infrequent PV watt drops on our axpert inverters.  😞

A few months ago I decided to install a remotely triggered cut-off switch, triggered by a Sonoff wifi switch that I am able to control from work or wherever.

I now have the ability, if I see that a dip has occurred, to cut the panel feeds remotely until the MPPT resets, and then connect them again.

This is probably not the best solution and does not solve the root problem, but has taken away the frustration of sitting at work and seeing that the input from the panels is zero and not having the ability to do something about it, now I have!

Regards

9 minutes ago, KobusC said:

Hi

I see no-one has come up with a solution to the infrequent PV watt drops on our axpert inverters.  😞

A few months ago I decided to install a remotely triggered cut-off switch, triggered by a Sonoff wifi switch that I am able to control from work or wherever.

I now have the ability, if I see that a dip has occurred, to cut the panel feeds remotely until the MPPT resets, and then connect them again.

This is probably not the best solution and does not solve the root problem, but has taken away the frustration of sitting at work and seeing that the input from the panels is zero and not having the ability to do something about it, now I have!

Regards

Hi Kobus,

I haven"t had that issue for a long time. I initially had my 12 panels split into 6 sets with 2 panels in series per set. I think this caused too much of a voltage drop under certain conditions, so I ended up connecting 3 panels in series, so that I ended up with 4 sets. 

I don't know what application you use to monitor your system, but the below Voltage on my system dropped too low:

I also currently have my 12 panels string up into 2 panels per set.

This is my voltage as right now, not sure if this is to low or not?

8 minutes ago, KobusC said:

I also currently have my 12 panels string up into 2 panels per set.

This is my voltage as right now, not sure if this is to low or not?

That Voltage is okay, but keep an eye on it. When the PV Watts go very high, you will see that Voltage drop as the Amps increase. I think mine went down to around 70V when I noticed the PV Watts drop out.

Pipes

 

Just had a trip around 12h00   😞

I was able to reset it though with my boer-maak-n-plan device  🤠

I constructed a graph showing the values at the trip time. The volts was at 95.1 and the watts at 3159w. Not sure what it means, does not seem to drop that low, unless it is in the 10 minute between measure zone.

I note that just before the PV freeze, the PV voltage was at the equal highest it's been all day. Given that you system possibly only monitors the PV voltage every 5-10 seconds, it's possible that the PV voltage exceeded 125 V. I don't know of any reason that this would trigger a PV freeze. At 130 V, it starts ramping down the PV power, linearly to zero at 145 V.

Your PV power looks very strange. It looks like the power was zero from 9-10:45am, for example. Does it really behave that way?

Coulomb

Sorry, it only appeared like that because I cropped the watts below 1000. Below is the complete graph for the day.

When the watts dropped to zero the volts was actually at 95.1 at that point. The input watts stayed at zero while the volts continues to appear, up to 120.2v at the moment I disconnected the panels at 13h02. At 13h10 I reconnected it when the voltage was also zero. Thereafter it continued normally until sunset. 

Not sure why the watts fall away but the voltage remains, does not make sense.

 

I have some thoughts:

Seems like this is some sort of fault induced by the fridge load. It could be a design fault. Or possibly the sudden current spike on the battery DC induces a voltage in the PV that pushes it over a limit or causes it to enter some protection state.

Do the solar and the battery wires share a conduit? Perhaps try moving them further apart or putting them in different conduits (preferably a metal one for the PV).

P1000

The PV and battery wires does not share a conduit, they are quite separate from each other.

If I have a look at the battery volts it was at 54.1v when the pvWatts drop occurred.

If your battery Volts were sitting at 54.1V at that time, then it is quite possible that your PV Watts will drop significantly, as the load is going to drop when your batteries are fully charged. It should not drop to zero, but mine drops to the current load requirement which is about 900W due to the pool pump running and other smaller things like the fridge etc.

Pipes

You are right, it does drop the pv watts to match the current load. In the above case however it drops to zero watts and never recovers unless with manual intervention or when the MPPT resets that night.

Do you have an Axpert King with early firmware perhaps? Sorry, no time to check back for this information. From poor memory, around 71.86 there were PV problems that were largely fixed in later firmware.

Hi Coulomb

Ssorry for not replying earlier, long weekend in SA  🙂

Yes I do (Feb2020 purchase).

It is a Voltex King 5KVA, not sure what firmware is on it. Will have a look tonight to see if I can find it.