On 2020/03/12 at 5:17 AM, Coulomb said:

So the maximum recommended discharge of 0.2C (sometimes written as C/5) is for you just 24 A, or about 600 W. With losses, you should only be drawing some 550 W. That's just 11% of your inverter's capacity. My point is, you need good discipline to stay under that load the vast majority of the time, even if your intentions are good.

 

Thank you. Just to make sure I understand, 0.2 (for me) means I should not be drawing more than around 550w at any one point. This is independent of the time period it is drawn over. This relates to the out (or in) flow of electricity from the battery, not how long it can sustain this output.

So to keep my battery in the best nick possible I should avoid stressing it by trying to draw too much from it at any one point...

 

1 hour ago, Lyle said:

Just to make sure I understand, 0.2 (for me) means I should not be drawing more than around 550w at any one point. This is independent of the time period it is drawn over.

Yes, exactly. It's an instantaneous thing. So the 0.2C limit is about amps, not amp·hours.

Though there is a separate limit to how much you take out over time as well; that's often stated as 50% of rated capacity (so 50% × 120 Ah = 60 Ah), though you get even better battery life if you restrict most discharges to 20% of capacity (20% × 120 Ah = 24 Ah).

Thank you so much.... 

 

I have an off grid setup using the above 5Kva Axpert inverters. 3 inverters setup for single phase with one Master and two Slave units. PV is supplied by 36 x 330W panels in 3 equal clusters feeding an inverter per cluster.  All is working well however what confuse me is the charging behaviour from utility/generator power source. While all three inverters will charge the battery with solar PV source, only the master will charge with utility/generator power and only with the 2 slaves disabled. Enable the 2 slaves and the system will show there is utility power however it simply won't use that source to charge.

Then disable the 2 slaves and the master will start charging again but intermittedly not continously as it does with PV supply.  Utility charge rate is set at 20Amp and the generrator is a 10Kva unit suppling a constant 230V at 50Hz.

I have not done the installation so I am still trying to figure out why this weird behaviour when utility power is supplied to the system. Any ideas?

16 hours ago, DSF said:

While all three inverters will charge the battery with solar PV source, only the master will charge with utility/generator power and only with the 2 slaves disabled.

That's weird. I note that the charger source priority, as well as the maximum utility and total charge current settings (settings 16, 11, and 02 respectively) are settings that don't automatically transfer from one machine to another. So it may be that the slaves have disabled utility charging, or set it to only 2 A. I would have thought that the master would still charge from utility when directed, even if the slaves don't.

Hi all i have a Mecer 5kva inverter and is totally off grid. No and then it needs a boost and so i start the generator. Tonight the generator only kicks in and out and no charge to batteries. Any ideas why. Worked fine before no suddenly its a no go

7 hours ago, RNEL said:

Tonight the generator only kicks in and out and no charge to batteries.

Perhaps the generator needs a tune up and/or governor adjustment?

If the generator output is only accepted for less than a minute at a time, that might explain the lack of battery charging. It takes a minute or so for the utility charger current to ramp up to noticeable levels.

Hi Everyone

Thanks for all the good tips.

Just added solar to my Mecer 5000 watt inverter.

12 x CNBM 6P-330 330W POLYCRYSTALLINE SILICON SOLAR PANE

4 strings x 3 panels each into a solar db board with fuses.

I am getting 1.2 kw on the inverter under pv input.

Is this right or did I connect something wrong as I thought I would get much more.

Thanks Wayne

 

 

Can anyone please assist me? 

I have a Mecer 5kVA inverter that keeps on tripping the power and giving me a error code 11 - "Main relay failed". Is this something that can be rectified by playing around with the settings or does it just mean that the inverter is on its way out? 

 

On 2020/05/08 at 12:04 AM, WayneSi said:

Hi Everyone

Thanks for all the good tips.

Just added solar to my Mecer 5000 watt inverter.

12 x CNBM 6P-330 330W POLYCRYSTALLINE SILICON SOLAR PANE

4 strings x 3 panels each into a solar db board with fuses.

I am getting 1.2 kw on the inverter under pv input.

Is this right or did I connect something wrong as I thought I would get much more.

Thanks Wayne

 

 

Hi Wayne, 

Are you still experiencing the low output from your panels? 

Remember the panels will only supply according to the load.

Orientation and angle of the panels also plays a role.

9 hours ago, francois said:

Are you still experiencing the low output from your panels?  ...

Orientation and angle of the panels also plays a role.

He also posted in the topic Solar Configuration. As you say, orientation is important; we convinced him to angle up his panels, and he has much better output now.

11 hours ago, Rusty Trader said:

I have a Mecer 5kVA inverter that keeps on tripping the power and giving me a error code 11 - "Main relay failed".

What model of Mecer 5 kVA inverter (there are several) is that? It seems to be mis-documented in some models' user manuals.

If you have an Axpert MKS II (Mecer SOL-I-AX-5NB), then it actually means "PV over voltage".

What is your PV voltage when this happens?

How many panels do you have in series and what model of panel are they? At least the Voc specification would be very helpful.

Thank you so much for the reply.

According to the quote I received from the installer it only shows: 330W Canadian panels but more information than that about the panels I do not have, ☹️. 

It does appear to be an Axpert or so again the quote suggests. Unfortunately I did not do the installation and or purchase the products to have any more information. I can however provide images of the inverter (once the sun comes up). Only 05:00 AM here in SA. 

I do have 10 of the 330W panels in series on the roof and the PV input voltage fluctuates between 239 - 240 V at any given moment. 

13 minutes ago, Rusty Trader said:

I do have 10 of the 330W panels in series on the roof and the PV input voltage fluctuates between 239 - 240 V at any given moment.

Is that at 5am? I would think that's before dawn at this time of year. Perhaps you're reading AC input voltage?

I did a quick search for Canadian Solar 330 W panels, and it gave a Voc of almost 46 V (at 25°C). That's nearly 460 V for 10, and it would be higher than that in early morning before the panels warm up yet have decent sun. The upper end of the MPPT range is 430 V; 450 V is the absolute maximum (capacitors could explode above that voltage).

My guess of what's happened is that the installer is used to Canadian Solar panels of around 300 W, and hasn't checked the specifications as the power of the available panels has crept up over the months. There was a big jump in Voc from the 310 W panels (60 cell, Voc around 40 V) to the 320 W panels (72-cell, Voc around 45 V).

So it looks like while 10 of the 310 W panels is fine, 10 of the 320 W panels is a little over specification, and 10 of the 330 W panels is way over, causing the fault code 11 to come up.

You would be better off with 2 strings of 5 panels, or if you have the roof space and can afford it, two strings of 6 panels. 12 x 330 = 3960 W, well within the 4500 W maximum allowed. Two strings of 7 panels would be just over the limit (4620 W, 2.7% over).

I hope you can get your problem sorted out satisfactorily.

Thank you, yes, I was reading the AC input voltage off the display. 

I was assuming that the panels were connected in series but now that you've mentioned it, my panels are stacked 5 in a row. 

1 hour ago, Rusty Trader said:

Thank you, yes, I was reading the AC input voltage off the display. 

I was assuming that the panels were connected in series but now that you've mentioned it, my panels are stacked 5 in a row. 

Hi Rusty,

Are they stacked 5 in a row on the roof? They could still all be connected in series that way.

I posted this as a new question and then realized it may be more appropriate here, since I started this thread many moons ago :-).

I am moving my noisy inverter out of the house, along with the batteries. I will be moving them outside into a small corrugated metal shed 3m from the DB board. Eventually I may upgrade to a 5Kw system, so I want to be sure my new cables will be sufficient.

My current Off-The-Grid system:

• Mecer SOL-I-AX-3MPlus48 Inverter/Charger
• 6-300W Enersol panels
• 2-US3000 Pylontech Batteries [less than one year old]
• Yamaha EF5500FW Generator

So what size cable from the inverter to the DB board [3m] would be sufficient, even for a 5Kw system?

I live in Swellendam, and the metal corrugated shed will be in the shade - any special considerations needed for the shed to house the inverter and batteries?

And if I wanted a bit more power, would it be better to add 2 more panels or one more battery?

Any other suggestions/recommendations?

3 hours ago, Jesse said:

So what size cable from the inverter to the DB board [3m] would be sufficient, even for a 5Kw system?

I would use 6 mm² for AC-in, and 4 mm² for AC-out. Reason for the difference being that the AC-in could be charging the battery as well as supplying the load through the 4 mm² cable.

3 hours ago, Jesse said:

And if I wanted a bit more power, would it be better to add 2 more panels or one more battery?

Hard to say; I think I'd go for 2 more panels.

Edit: that's to be able to supply more energy to loads from PV over the course of a typical 24-hour period; if you literally wanted more power (i.e. the ability to supply higher-powered loads, or more loads at once), then more battery is what you need.

Edited December 11, 20205 yr by Coulomb

Thanks Coulomb

Regarding adding two more panels, my current system has two sets of 3-300w panels [in series] wired in parallel [see attached].

Can I just add one more panel to each series?

7 hours ago, Jesse said:

Can I just add one more panel to each series?

Eek. I assumed that you had the panels wired 2S3P, so you just add another pair in parallel.

If your panels are 72-cell, it's already too high in voltage. But 300 W panels may be 60-cell, in which case it's OK.

But you definitely can't run 4S (which is what you end up with if you do as suggested above).

If they are 60-cell, your best bet is to add three new panels, all in series, in parallel with the two existing strings.

If they are 72-cell, your best option is to rewire them as 2S4P; then you don't need (and can't use) a third panel.

They are all 72 cell, and I'm curious why that makes a difference?

I set them up as per sustainable.co.za's instructions, as I bought the last three panels from them:

"The panels will need to be connected in 2 parallel strings of 3 panels in series due to the maximum voltage parameters of the built-in MPPT charge controller in your inverter."

And I'm glad to change the configuration to your recommendation if I add two panels, which I believe would generate maximums of about 73 volts and 33 Amps, but would you suggest I change to a 2S3P configuration if I keep with my existing 6 panels?

 

On 2020/12/13 at 11:34 PM, Jesse said:

They are all 72 cell, and I'm curious why that makes a difference?

The more cells in series, the higher the panel voltage, both open circuit and under load. 3S means 3 x 72 = 216 cells in series, which will be about 216 x 0.6 = 130 V open circuit at 25°C, just as derating is starting. At 0°C, you usually get about 7% more voltage, which is about 139 V. Modern panels usually go a little higher voltage than this.

With the PV voltage so high, the buck controller has to work harder to chop it down to battery voltage, and that makes it run hotter. This reduces life of the capacitors, and causes the firmware to cut back the power when the SCC heats up. All in all, you are far better off with 2S than 3S (72-cell panels only).

With 60-cell panels, you need 3S to get adequate voltage from the panels under lower light conditions, and the 17% fewer cells means 17% lower voltage, more head room, and lower temperature.

On 2020/12/13 at 11:34 PM, Jesse said:

I set them up as per sustainable.co.za's instructions, as I bought the last three panels from them:

"The panels will need to be connected in 2 parallel strings of 3 panels in series due to the maximum voltage parameters of the built-in MPPT charge controller in your inverter."

Interesting. They obviously haven't tried it on their own inverters.

On 2020/12/13 at 11:34 PM, Jesse said:

And I'm glad to change the configuration to your recommendation if I add two panels, which I believe would generate maximums of about 73 volts and 33 Amps, but would you suggest I change to a 2S3P configuration if I keep with my existing 6 panels?

Yes, always 2S for 72-cell panels, if using 145 V absolute max SCCs.

I should put that in my signature. Oh, wait...

Thanks Coulomb - I really appreciate your thoroughness.

Happy Holidays!

One more question

I do want to add two more panels to my 6-300watt panel system, but there seems to be a lack of 300watt panels.

Are there cons to adding 2-315watt panels?

5 hours ago, Jesse said:

Are there cons to adding 2-315watt panels?

Yes. If the Vmps differ by more than 5%, don't do it. 315 is exactly 5% more than 300, so it depends on whether the extra power is the result of "all voltage" or "some current". With differing Vmp, none of the panels will be running near their optimum power point, and array output will suffer. I think that there are some safety issues as well, in case a string shorts and all the other strings dump their current into it. Of course, each string needs its own PV rated fuse.

Also, to add just two panels, your existing panels will have to already be wired 2S. But with 300 W panels, that's likely already the case.

The larger panels may have a different size or appearance, which might be a consideration.