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Axpert 3Kva inverter PV charging intermittently


PhillipvdM
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Good day all,

My setup is as follows:

1. Axpert 3Kva Inverter 

2. 2 x CNBM 330w solar panels

3. 4 x Oliter 12V 100ah batteries, 2 in series and 2 in parralel to give 24V

The settings is set on SOL, battery on AGM. The PV charges intermittently even though the batteries are not full. Any ideas?

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6 hours ago, PhillipvdM said:

The settings is set on SOL, battery on AGM. The PV charges intermittently even though the batteries are not full. Any ideas?

Well, you only have 660W nominal of panels, so a lot of the time the loads will probably be using all the available PV.

Beyond that, all Axperts with factory firmware have the premature float problem. There is no patched firmware for 24V models that would fix it. I suspect that having such low PV triggers the premature float bug more often and sooner. Depending on firmware features, you could work around it with timed absorb or the equalisation settings. Does your firmware have either of those features? My impression is that lower power models (less than 5kVA) often don't have either feature. If so, you might try more panels, or consider a separate charge controller.

Edit: another possibility is that your PV voltage may be too high or too low for your model.

Edited by Coulomb
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Thanks for the replies. The panels is connected in series and if it is not charging is shows an input voltage of between 79 and 82 volts with sunshine on it. 

The loads will never reach 660W as we are running some LED lights (5), 3 x standing fans, 50watt each and a 100Watt fridge.

no timed absorb or equilisation settings. Would I have to out more panels in parrallel to boost the charge ampere?

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Thanks Guys,

I got the PV to charge, my batteries now however is not charging fully, it only charges to 25.6V. My float charge is set to 27V and bulk to 28.4V. Any ideas why it is not fully charging?

Battery specs:

Oliter 12V 100ah batteries, two in serie and two in parralel. Float charge 13.4 to 13.7V and average charge 14.1 to 14.4V.

Happy new year to all.

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5 hours ago, PhillipvdM said:

it only charges to 25.6V

That's an average of 12.8 V per 12 V module. That's the voltage you'd expect from a fully charged lead acid battery module, if it's not being charged (or more than very lightly discharged). Was the 25.6 V at night?

The other thing is that you have a 200 Ah battery, and about 500 W of charging (about 20 A). So it will take about 10 hours to take the battery from dead flat to full, or about 5 h from 50% discharge. You'll only get the full 20 A at close to noon, it it will take more than a day to recharge your battery. When you factor in about 25 W of continuous self consumption 24/7, it will take even longer. The drain will be a little less than that when the inverter proper (the DC-AC converter) is not operating.

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Thanks Coulomb,

Its gel batteries. The 25.6 was at noon with no load on it. It discharged through the night to 22.5V and switched off, running a 100W fridge and two 50W fans, this does not make sense. I am now trying to boost the batteries through a generator, this also seems like its not working. 
 

Is my float and bulk settings correct?

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Also if its not too much of a hassle can you please review my settings:

 

1 - SBU

2 - 20A

3 - UPS

4 - SDS

5 - USE

11 - 20A

12 - 25.5V

13 - FULL

16 - SNU

26 - 28.6V

27 - 27.2V

29 - 22.5V

 

thanks for all the help so far

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1 hour ago, PhillipvdM said:

The 25.6 was at noon with no load on it.

And was it charging at that time?

What charge current?

Are your panels angled at an appropriate tilt and orientation?

Is your inverter's solar charger perhaps one of the 75 V max models? In that case, you need to rewire your panels in parallel.

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It discharged through the night to 22.5V and switched off,

It's not good to let them run that low often. 22.5 V is an emergency cutoff, for extreme situations.

Quote

running a 100W fridge and two 50W fans, this does not make sense.

Your 660 W panels are a bit light, even for this light load. 

Is your inverter perhaps a clone?

Quote

I am now trying to boost the batteries through a generator, this also seems like its not working. 

Axpert-like inverter-chargers are notoriously picky about generator waveform quality. You might need to start the generator with a small load, until the inverter can take over other loads.

Quote

Is my float and bulk settings correct?

Yes, and your other settings seem fine. You could perhaps increase setting 02 (maximum total charge current) to 30 A. This may have a small effect near noon.

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28 minutes ago, Coulomb said:

And was it charging at that time?

What charge current?

Are your panels angled at an appropriate tilt and orientation?

Is your inverter's solar charger perhaps one of the 75 V max models? In that case, you need to rewire your panels in parallel.

It was cahrging yes. 9 amp charge current. Panels is fine. I will have to rewire the panels in parralel yes.

 

29 minutes ago, Coulomb said:

Your 660 W panels are a bit light, even for this light load. 

The batteries max charge amps is 20amp so more panels might not work? When I put the two 330W in parralel, I should get 20AMP or close to it

 

30 minutes ago, Coulomb said:

Is your inverter perhaps a clone?

Seems like it is a clone yes. What does that mean. Time for a new inverter?

 

31 minutes ago, Coulomb said:
Quote

 

Yes, and your other settings seem fine. You could perhaps increase setting 02 (maximum total charge current) to 30 A. This may have a small effect near noon.

As my batteries can only charge with max 10AMP, thus in parralel 20AMP. Will this setting make a change?

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On 2021/01/02 at 12:26 AM, PhillipvdM said:

It was charging yes. 9 amp charge current. Panels is fine. I will have to rewire the panels in parralel yes.

Are you saying that you do indeed have a 75 V max PV solar charge controller?

On 2021/01/02 at 12:26 AM, PhillipvdM said:

The batteries max charge amps is 20amp so more panels might not work?

Usually lead acid battery modules can charge at up to 0.15C; for yours, that would be 15 A per module or 30 A for your whole battery. Are you saying that your modules specifically say not to charge at more than 10 A each?

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When I put the two 330W in parralel, I should get 20AMP or close to it

As long as you have an MPPT charge controller (not a PWM one), and if you don't have a voltage ceiling issue, it should not matter if your panels are in series or parallel. But it sounds like it will be best for your system to have the panels in series.

20 A at ~25 V is ~500 W, but you have losses and some loads, so yes your 660 W of panels will max out your system, in ideal light conditions. But those only exist for a few hours a day, and even in those hours, there are often clouds or the angle of the panels isn't ideal, so you could do with a third panel. 1S3P. That's if your solar charge controller can cope with 990 W nominal of panels. It it's a clone, who knows.

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Seems like it is a clone yes. What does that mean. Time for a new inverter?

Not necessarily. Some clones work just fine; the  problem is the uncertainty of the quality of the components, and what the firmware is doing.

Quote

As my batteries can only charge with max 10AMP, thus in parralel 20AMP. Will this setting make a change?

If you battery modules really can only take 10 A of charge current, then you should not change the maximum charge current to more than 20 A. The battery won't limit itself to 20 A, you need to make the inverter-charger do that. It might still be worthwhile having 3 panels, so that you get to charge your battery at close to 20 A for more of the day, and even in cloudy conditions. But note that some  solar charge controllers will overshoot their battery voltage and current settings if the PV array is too high in power. Perhaps post a photo of the sticker on the side of your inverter (if there is one), which has a brief summary of the most important ratings.

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