Mecer 5KVA Solar Performance Issues?

[Kalito]

I've two arrays connected to the inverter facing east and north (just discovered and innovated a wall mount for the north wall, can only accomodate 6 panels). The arrays are in strings which have 2x series (VOC close to upto 76 range recommended in manual and Vmp about 61still within range). From the attached ICC screen capture the voltage curve seems to be acceptable especially that I monitored early morning. Temperature is comfortable despite the onset of the dry season with day time temp peaking around 30 degrees. Infact as the day progresses the PV voltage flatlines around 68V. What seems odd though is the current which was all over the place. Is this normal?

Question: Is there any benefit in puting the panels in 3x series? I note reading about that most seem to have them in this style.

I also monitored the PV early morning generation (thanks to ICC) and one load aspect caught my attention. The main frige, A Defy Refrigerator with a rating of A+ and a stated annual consumption of 478kWh per annum and name-plate consumption of 150W (see attached pics) seems to have a very high starting watt draw which spiked the load by 1kWh. This has been consistent, each time this fridge starts for milliseconds it spikes this high. However, the 0.5HP sump pump (circulates fish pond water) has a modest spike a fraction of the fridge despite a higher continous running draw.

Question: Is this seemingly normal for a 150W rated fridge to start with such a high surge? I know about motor surges but this is about 6x its rating!

[___]

1 hour ago, Kalito said:

Question: Is this seemingly normal for a 150W rated fridge to start with such a high surge? I know about motor surges but this is about 6x its rating!

Rule of thumb for an induction motor is 5x nominal. It rings true for my A++ rated fridge (90W compressor, peaks at 450W) as well as the A-rated freezer (which also has a 90W compressor). 150*5 is around 750W. Often the current sensors on the inverters aren't that accurate either. So it doesn't seem that far off to me.

[Sidewinder]

Yes, I wouldn't worry too much about those startup peaks.

I do think you need/could optimise the whole system for longevity etc.

Not mentioned but I would look at the following:

1) Because your array is split, each direction should be on it's own MPPT for max. performance. Means another Axpert in parallel.

2) You don't mention if you have a BMV, but using the Axpert's SOC is as handy as a A+++ fridge on the South Pole! You already have ICC, so use it's capabilities to control the Axpert.

3) Also discussed here on the forum, but a Battery Balancer is best for longevity of your bank, specially if you run of battery during the night. 

[Kalito]

3 minutes ago, Sidewinder said:

Yes, I wouldn't worry too much about those startup peaks.

I do think you need/could optimise the whole system for longevity etc.

Not mentioned but I would look at the following:

1) Because your array is split, each direction should be on it's own MPPT for max. performance. Means another Axpert in parallel.

2) You don't mention if you have a BMV, but using the Axpert's SOC is as handy as a A+++ fridge on the South Pole! You already have ICC, so use it's capabilities to control the Axpert.

3) Also discussed here on the forum, but a Battery Balancer is best for longevity of your bank, specially if you run of battery during the night. 

Great points. Noted on the two arrays and working on it. However, I intend to replace the Mecer with something which will make me actually use the max PV production even as it switches to utility for support. A BMV is in the pipeline.

Batt balancer seems to be what I need especially as I look to adding another bank or when I rob a bank (shhh) and add lithium instead.

Question: I am fairly new to this but what are the Axpert best battery charging settings? Any ideas?

[Kalito]

21 minutes ago, plonkster said:

Rule of thumb for an induction motor is 5x nominal. It rings true for my A++ rated fridge (90W compressor, peaks at 450W) as well as the A-rated freezer (which also has a 90W compressor). 150*5 is around 750W. Often the current sensors on the inverters aren't that accurate either. So it doesn't seem that far off to me.

Thanks man that is a relief!

[Sidewinder]

Just search for Chris Hobson's guide on the Axpert Setting on the forum. Just a few more post to get to 15!!

[Chris Hobson]

2 hours ago, Kalito said:

Question: I am fairly new to this but what are the Axpert best battery charging settings? Any ideas?

Battery charging settings are determined by the specs of the batteries.There is no best setting. AGM and Gel batteries generally have lower bulk voltages than lead acid batteries and higher float voltages, but that is the problem with general settings - they are general. Better to use the battery spec sheet. Again AGM and Gels can handle a higher charging rate than lead acid's recommended C/10 rating but again be guided by the spec sheet.

[Kalito]

2 hours ago, Chris Hobson said:

Battery charging settings are determined by the specs of the batteries.There is no best setting. AGM and Gel batteries generally have lower bulk voltages than lead acid batteries and higher float voltages, but that is the problem with general settings - they are general. Better to use the battery spec sheet. Again AGM and Gels can handle a higher charging rate than lead acid's recommended C/10 rating but again be guided by the spec sheet.

At 250Ah 25A should do? See spec sheet and kindly advise

6-FM-250 (GP).pdf

[Chris Hobson]

42 minutes ago, Kalito said:

At 250Ah 25A should do? See spec sheet and kindly advise

6-FM-250 (GP).pdf

I see it is one of those high charge AGM batteries. Max charging 62A. So you can open the taps on these batteries. Bulk between 57.6 and 59.2V (at 20^oC) and float 54.4 -55.2V. I would use the lower end of these values since one is above gassing voltage. I would further lower the bulk voltage by 0.6V if ambient temperatures are 25^oC and by 1.2V if ambient temperatures are 30^oC. Float I would lower by 0.4V at 25^oC and 0.8V at 30^oC. The GP range are "general purpose" so basically standby batteries. I don't think they are going to last for a long time. It may be difficult to source "true" solar batteries in Zambia.

[Kalito]

4 hours ago, Chris Hobson said:

I see it is one of those high charge AGM batteries. Max charging 62A. So you can open the taps on these batteries. Bulk between 57.6 and 59.2V (at 20^oC) and float 54.4 -55.2V. I would use the lower end of these values since one is above gassing voltage. I would further lower the bulk voltage by 0.6V if ambient temperatures are 25^oC and by 1.2V if ambient temperatures are 30^oC. Float I would lower by 0.4V at 25^oC and 0.8V at 30^oC. The GP range are "general purpose" so basically standby batteries. I don't think they are going to last for a long time. It may be difficult to source "true" solar batteries in Zambia.

You are quite right on the standby aspect and domestically there are several battery brands. What is your view of Vision batteries? I see you use CBs. How have they been treating you? I am flogging off the genset as it is idle and big (got good deal at the time we were having 10hr load-shedding. With solar I only run it to keep it active. Only done about 225hrs. Idea is to get the right batteries. Perhaps even lithium.

Temperatures are now around 25-30. The Axpert bulk is around 56V and float 54V.

[Chris Hobson]

21 hours ago, Kalito said:

Question: Is there any benefit in putting the panels in 3x series? I note reading about that most seem to have them in this style.

Yes the higher the voltages the lower your losses. With an Axpert the general rule is 3 in series for 60 cell panels (which you have) and 2 in series if they are 72 cell panels. A lot of folk do have 72 cell panels in series of three . The danger is less in South Africa since we cold mornings and as the sun comes up temperatures warm as opposed to temperate Northern hemisphere regions where the sun can be shining brightly while the temperatures are sub zero. 

8 hours ago, Kalito said:

You are quite right on the standby aspect and domestically there are several battery brands. What is your view of Vision batteries? I see you use CBs. How have they been treating you? 

Vision battery specs seem OK better than the CB Solars I have. I think the king of the cheaper AGM/Gel batteries are is Omnipower. Companies like Hoppecke, Trojan and Victron make good Gel batteries but they come at a price. My CB Solars have done their allotted time an I too am in the market for new batteries. 

You should probably look at these reviews

 

9 hours ago, Kalito said:

Temperatures are now around 25-30. The Axpert bulk is around 56V and float 54V.

Bulk 56.4V Float  53.6V

[Kalito]

On 23/09/2017 at 7:59 AM, Chris Hobson said:

Yes the higher the voltages the lower your losses. With an Axpert the general rule is 3 in series for 60 cell panels (which you have) and 2 in series if they are 72 cell panels. A lot of folk do have 72 cell panels in series of three . The danger is less in South Africa since we cold mornings and as the sun comes up temperatures warm as opposed to temperate Northern hemisphere regions where the sun can be shining brightly while the temperatures are sub zero. 

Vision battery specs seem OK better than the CB Solars I have. I think the king of the cheaper AGM/Gel batteries are is Omnipower. Companies like Hoppecke, Trojan and Victron make good Gel batteries but they come at a price. My CB Solars have done their allotted time an I too am in the market for new batteries. 

You should probably look at these reviews

 

Bulk 56.4V Float  53.6V

Thanks this is extremely helpful. Will adopt/use

[___]

On 9/22/2017 at 10:46 AM, Sidewinder said:

Means another Axpert in parallel.

Or just another MPPT. Because of the way the Axpert works (batteries are tied directly to the low-voltage DC bus inside the inverter), you can use any suitable MPPT and just tie it directly to the batteries. A BlueSolar 150/35 is around 5k as I recall.

[Kalito]

On 26/09/2017 at 11:31 AM, plonkster said:

Or just another MPPT. Because of the way the Axpert works (batteries are tied directly to the low-voltage DC bus inside the inverter), you can use any suitable MPPT and just tie it directly to the batteries. A BlueSolar 150/35 is around 5k as I recall.

@plonkster I missed your interesting reply till now. This is interesting. So the MPPT is tied directly to the batteries simulating another bank according to the Axpert?

[Kalito]

On 22/09/2017 at 11:01 AM, Sidewinder said:

Just search for Chris Hobson's guide on the Axpert Setting on the forum. Just a few more post to get to 15!!

@Chris Hobson I found your Axpert settings pdf very useful and have used your settings. However, on SOL setting my Mecer (Axpert) doesn't do what you indicate in the text. When set to SOL it will indeed prioritise solar to supply the load but immediately the load is higher than PV production the Inverter goes to bypass and hence AC. SBU is what makes the Inverter tap into batt. before changing over to AC.

In the settings text an example is given that if say PV is 30W the inverter will draw from battery and operate as though PV is sufficient. My experience with SOL setting disagrees. My inverter immediately switches to AC if PV is not sufficient or if load is higher than PV.

[___]

3 hours ago, Kalito said:

So the MPPT is tied directly to the batteries

The Axpert puts an inverter and an MPPT into one case, but internally the output of the MPPT and the input to the inverter are tied to the same bus which is in turn connected to the batteries. It's exactly the same as the more traditional "external mppt" model, except the connections are neatly hidden. That... and the inverter can control the power levels of the MPPT for self-consumption purposes.

Adding another external MPPT cannot of course be controlled by the inverter, so it isn't exactly the same... just very close.

[Kalito]

20 hours ago, plonkster said:

The Axpert puts an inverter and an MPPT into one case, but internally the output of the MPPT and the input to the inverter are tied to the same bus which is in turn connected to the batteries. It's exactly the same as the more traditional "external mppt" model, except the connections are neatly hidden. That... and the inverter can control the power levels of the MPPT for self-consumption purposes.

Adding another external MPPT cannot of course be controlled by the inverter, so it isn't exactly the same... just very close.

I do not want to take it for granted that I have understood you in respect to the connection. I see @Chris Hobson loves your comment too. Now explain as though to a dummy. I understand the common bus thingy but I am visualising the operational practicality of it. MPPT linked to the battery in parallel (effectively making the bank always full) and sending the juice to the inverter making it see plenty power for self-consumption? In SBU (Solar>Battery then Utility) consumption (Chris your preferred setting) effectively makes the Axpert maximise the available juice including from our virtual battery? In the event that the battery is discharged the external MPPT supplies the watts assuming enough array generation? The North facing array is 1,560W (260x6) peak the east facing is effectively 1,530 (255x6). I must mention that I have a "spare" 5kVA which I could probably hookup but I am thinking more of the future (personal preference really).

My intention is to replace with a wifi-enabled router (for monitoring) such as an Imeon/Goodwe which can properly handly self-consumption (only get from utility the top-up to solar). But for now to max my current situation at fair cost the external MPPT sounds exciting if I understand correctly.

There is a local distributor of Morningstar, Outback, Midnite and Magnum. What model fits your pref of Blue Solar closest?

[___]

Okay, let me lay some ground work first. In the old days you worked out how much storage you needed. Then you worked out how big the solar array had to be to properly charge the batteries, but not so big that it overcharges it.

So if you had a 200Ah battery, you had to either size the array so that it won't go over 35A, or you had to install a charge controller that allows you to configure a limit. It is common to slightly oversize the array, but that limit remains.

This had a downside. What if you had 50 amps available, and enough loads that you could dump 20 amps directly into the loads and leave the other 30 for charging the batteries? That would be a safe situation, would it not? Unfortunately, with the traditional setup, you'd hit the limit on the MPPT (at 35), you'll use 20 for the loads and charge at 15, wasting the other 15 amps.

One thing the Axperts brought to the tables -- and it did so very cheaply -- is a dynamic current limit on the MPPT. There is constant comms between the inverter and the MPPT to ensure that consumption is added into the calculation. In other words, you can now put up an array that can push 50 amps, configure it for a safe max of 35, and if there is a load that wants 20 amps, it will increase the limit on the MPPT to 50A so that everything is used while the batteries are still protected from a high charge rate.

That is the first half of the story. Second half, also using the traditional setup. You'd have the MPPT as a separate unit, and it would have its own cables going directly to the battery (via the proper breakers and fuses and all that, not important here). The inverter, also a separate unit,  would be connected directly to the battery as well (also via the correct fuses and disconnects and what have you). So essentially the MPPT output, the inverter input, and the battery bank are all wired together in what you might call parallel, and it's visually apparent to you since you can see the cables.

What I am saying is that internally, inside the Axpert, they did the same thing. The MPPT is wired directly to the battery just like we did in the old days. The inverter is wired directly to the battery, just like in the old days. It's just neatly hidden inside the case.

In the olden days (and even now with some setups), when you had two arrays pointing in different directions, you use separate MPPTs with them. Each one simply connects to the battery (again, fuses and disconnects.... pffft). Incoming power goes into the battery, outgoing power goes to the inverter. Any difference between the two goes into (or out of) the battery. The battery itself is the hub, like a big old holding dam.

Now what I am saying is that the fact that the MPPT is inside the case with the Axpert doesn't prevent you from adding another one externally. It's exactly like in the old days... EXCEPT... that nice feature I mentioned first... you don't have that. That second MPPT, if it is big enough, can cause the battery to overcharge. If the battery is big enough, no problem. If your batteries are small... then that might be a problem.

[Kalito]

Makes a lot sense seeing that we have two charging points i.e the two MPPTs which are not essentially in sync. But is it a simplistic view to assume that both Axpert and external MPPT will see that the battery is full and hence pass-thru?

You had earlier given a Blue Solar 150/35 as an option for such an operation. Would you be in a position to give a Morningstar, Midnite, Magnum alternative if you don't mind? I ask because I have local dealer for these brands and the cost-benefit analysis will inform my decision moving forward.

[Chris Hobson]

23 hours ago, Kalito said:

@Chris Hobson I found your Axpert settings pdf very useful and have used your settings. However, on SOL setting my Mecer (Axpert) doesn't do what you indicate in the text. When set to SOL it will indeed prioritise solar to supply the load but immediately the load is higher than PV production the Inverter goes to bypass and hence AC. SBU is what makes the Inverter tap into batt. before changing over to AC.

In the settings text an example is given that if say PV is 30W the inverter will draw from battery and operate as though PV is sufficient. My experience with SOL setting disagrees. My inverter immediately switches to AC if PV is not sufficient or if load is higher than PV.

I have never had the need to test SOL as I run off-grid. If it goes into bypass under what conditions does it return to PV?

 

 

[___]

3 hours ago, Kalito said:

But is it a simplistic view to assume that both Axpert and external MPPT will see that the battery is full and hence pass-thru?

Axpert looks at the voltage, at least with the right program configured (I'm not familiar with it). It doesn't care which MPPT is raising the voltage, whether it be the internal or external one.

Where there is a BMV involved and maybe a bit of third party software (like ICC), you should of course make sure that the external MPPT also goes through the shunt so that the current is seen.

3 hours ago, Kalito said:

You had earlier given a Blue Solar 150/35 as an option for such an operation. Would you be in a position to give a Morningstar, Midnite, Magnum alternative if you don't mind? I ask because I have local dealer for these brands and the cost-benefit analysis will inform my decision moving forward.

I'm not familiar with the other brands. I know Midnight, Morningstar and Outback are very good reputable brands. They are usually more expensive than the BlueSolar (where I live). The cheaper MPPTs (again, where I live) are lower  quality and do not represent enough of a saving to take them over the BlueSolar.

For example, the other MPPT I know well is the Microcare unit. That's a single sync buck converter, and it costs more than 5k for a 40 amp unit. For 5 the same price I can get the 150/35, which is a double async buck converter (interleaved), in other words much lower ripple, and has a 5 year warranty. That's why I recommend this one, but it doesn't necessarily mean the others are bad :-)

[Kalito]

3 hours ago, Chris Hobson said:

I have never had the need to test SOL as I run off-grid. If it goes into bypass under what conditions does it return to PV?

Aah I think from my experience this manual statement is incorrect unless there is something amiss somewhere. PV completely goes around 18:30hrs (starts around 05:30hrs) this time of the year. I just took some screen shots of the readings which reveal very interesting issues about the manual statement:

According to the manual Utility provides power if any one condition happens:

Solar energy is not available (in this image solar energy is available but not sufficient)

Battery voltage drops to either low-level warning (not the case)

or the setting in program 12 (I have this set to 48V)

When the inverter searches for PV watts and they are above the load+batt (I notice battery typical float is 54W) or whatever battery + load is at the time the inverter disables utility.

Maybe the battery voltage did dip below 48V triggering Utility and I caught it at the moment when Batt was on its way to 53.6V float! I now have something to monitor tomorrow though.

[WilliamS]

Hi Guys. I have a 5kva Mecer inverter charger connected to 6 x 320w panels in series. The battery is a 48v Li-iron Leoch 100AH. The battery is full at about 11.30am (normal sunlight) and seems fine in terms of normal usage from the household appliances. But at some point between 2pm and 3pm the battery stops receiving charge and by 5pm is on less than 50% of its charge. If I reset when it stops charging, it will resume normal operation ie keep the battery at between 96 and 100% until the sun goes down. This happens frequently, but not everyday. I've checked that the inverter is programmed to supply the household requirement first and extra power is diverted to charge the battery. We generally use less power than is being generated by the panels, yet once the battery is full the inverter stops charging the battery (which is correct) but doesnt resume charging even when battery is below 75% and there incoming charge is more than the amount required for the household. Any possible solutions? 

[Coulomb]

On 2020/07/11 at 12:49 AM, WilliamS said:

But at some point between 2pm and 3pm the battery stops receiving charge and by 5pm is on less than 50% of its charge.

This has happened before.

* Is it a King compatible model?

* What main firmware are you running?

I think that the Kings (or was it MKS IIs?) had a problem with older firmware that caused this. Fortunately, more recent firmware is available for these two.