Jump to content

Axpert 5kva


Alec Swanepoel

Recommended Posts

7 hours ago, The Terrible Triplett said:

I have a question:
Presuming the 3 panels in series ( 29.5v per panel), so 88.5v @ 750w max 8.14amps per panel on a good day, for losses must also be accounted for, is that enough to charge the 48v 204ah bank?

For as Chris also said, min charge should be 20amps, yet the panels, as per Chris, can do max +-15amps, for on average 5.5 hours per day (being the annual average of good sunshine) which becomes worse if loads are powered at the same time, then batteries are definitely not getting enough amps to charge properly.

5% charge rate is for weekend only use, has the whole 5 days to recharge.
10% charge rate is for general daily use.
13% charge rate is best for off-grid with loads.
You have to get the batteries fully charged every day if they are used every night, so min 10%, max 13%.

 

Alec, another thought to ponder on: When the batts need replacement one day, get max 4 batteries with the AH rating you need.

Thanks - everything everybody commented makes perfect sense

I'm getting the picture..........

Arandoza, you are hitting the nail where it hurts...... more panels.... and still more panels. At the moment I'm doing more battery damage than saving money.

Thanks again!!!

Link to comment
Share on other sites

Thanks - everything everybody commented makes perfect sense

I'm getting the picture..........

Arandoza, you are hitting the nail where it hurts...... more panels.... and still more panels. At the moment I'm doing more battery damage than saving money.

Thanks again!!!

Yes thank you. I agree

Sent from my SM-G920F using Tapatalk

Link to comment
Share on other sites

What you guys are talking about is called oversizing the array. It works, your MPPT will just push the panel into territory where it makes less power, to keep it under the controller maximum (or the configured maximum, some controllers can have the maximum configured to a lower value).

How it does this depends. Some do it by pushing up the voltage above Vmp, The closer you get to Voc, the lower the current goes because at Voc the current is zero, by definition. This means you have to be certain the Voc is well within limits of the controller :-)

Link to comment
Share on other sites

Hi Alec,

I think the panels are the cheap bits :) as they last so long.

The batteries are the expensive bits and need to be replaced ultimately.

My thinking being that if I can save the daytime power for now and have enough battery for backup if Eskom drops :) I am happy.

I also run my Axpert on solar only or solar first, rather than SBU as this seemed to cycle the batteries a lot.

Whereas now on a clear day they appear to cycle twice a day early morning and then late afternoon.

JDP's software had some settings that allowed one to force the inverter to switch to solar later in the morning to avoid discharging batteries when the sun was rising or setting, by switching back to Eskom, from what I understand. I think it has some definite merit. But I am missing a Bmv 702 to

Take advantage of it :)

Also consider that during the day your panels have to run the load and charge the batteries, so one always needs more panels to power it all. I have often observed mine generating 2400watts, while I am only using around 800-900 Watts on load during the day, especially once the clouds have passed and the unit seems to try and recharge the batteries. It occasionally tries to bulk charge to your cv voltage 58.4 volts for example, this is when you see the panels producing the most :)

The one thing I can say is that my "times tables" have improved dramatically in the 1-36 amp X 64-98.2 volt range to calc the watts being generated on the fly :)

I am also thrilled by Chris's post with article on more strings being possible ? It looks really promising and may save me on an additional Mppt or second Axpert. Will still investigate further before "letting the smoke out" as one of the esteemed members has coined the phrase.

Have a great evening all.

Link to comment
Share on other sites

Hi Alec,

I think the panels are the cheap bits [emoji4] as they last so long.

The batteries are the expensive bits and need to be replaced ultimately.

My thinking being that if I can save the daytime power for now and have enough battery for backup if Eskom drops [emoji4] I am happy.

I also run my Axpert on solar only or solar first, rather than SBU as this seemed to cycle the batteries a lot.

Whereas now on a clear day they appear to cycle twice a day early morning and then late afternoon.

JDP's software had some settings that allowed one to force the inverter to switch to solar later in the morning to avoid discharging batteries when the sun was rising or setting, by switching back to Eskom, from what I understand. I think it has some definite merit. But I am missing a Bmv 702 to

Take advantage of it [emoji4]

Also consider that during the day your panels have to run the load and charge the batteries, so one always needs more panels to power it all. I have often observed mine generating 2400watts, while I am only using around 800-900 Watts on load during the day, especially once the clouds have passed and the unit seems to try and recharge the batteries. It occasionally tries to bulk charge to your cv voltage 58.4 volts for example, this is when you see the panels producing the most [emoji4]

The one thing I can say is that my "times tables" have improved dramatically in the 1-36 amp X 64-98.2 volt range to calc the watts being generated on the fly [emoji4]

I am also thrilled by Chris's post with article on more strings being possible ? It looks really promising and may save me on an additional Mppt or second Axpert. Will still investigate further before "letting the smoke out" as one of the esteemed members has coined the phrase.

Have a great evening all.

What is the difference between solar only and the sbu ?

Sent from my SM-G920F using Tapatalk

Link to comment
Share on other sites

What is the difference between solar only and the sbu ?

Sent from my SM-G920F using Tapatalk

Well solar first is for the charging of the batteries when it's available. And my output priority is solar.

The solar first means that when it discharges the batteries and switches back to Eskom to carry the load, it will continue to use solar to try and charge the batteries, until night and then it uses Eskom to charge. This means that Late in the afternoon the batteries hit the low level, inverter switches to Eskom, but keeps using the solar to charge the batteries, which means that I squeeze as much from the solar as possible back into the batteries.

When on Solar/battery/utility and utility + solar, it appeared the Axpert would

Discharge batts around 3:30

Pm when load is more than solar, deplete batteries, switch over to Eskom, then recharge the batteries from Eskom and solar, so charge them faster and because solar was still available

Although only 80w maybe it would begin this SBU cycle again.

Where as on the solar first it slowly charges, and it's unlikely to recharge them fully before the sun goes down, so one stays on Eskom a bit longer for the load, and only Once no solar the eskom charging kicks in. So less cycling in the afternoon.

This is where oversizing the Pv panels would also help me :) especially in winter.

Link to comment
Share on other sites

Thanks Chris. Its still a bit confusing for me. I use sbu but was alway wondering whats the difference as my manual does not explain it well. How much do you produce on a good day?

Sent from my SM-G920F using Tapatalk

Link to comment
Share on other sites

Well solar first is for the charging of the batteries when it's available. And my output priority is solar.

The solar first means that when it discharges the batteries and switches back to Eskom to carry the load, it will continue to use solar to try and charge the batteries, until night and then it uses Eskom to charge. This means that Late in the afternoon the batteries hit the low level, inverter switches to Eskom, but keeps using the solar to charge the batteries, which means that I squeeze as much from the solar as possible back into the batteries.

When on Solar/battery/utility and utility + solar, it appeared the Axpert would

Discharge batts around 3:30

Pm when load is more than solar, deplete batteries, switch over to Eskom, then recharge the batteries from Eskom and solar, so charge them faster and because solar was still available

Although only 80w maybe it would begin this SBU cycle again.

Where as on the solar first it slowly charges, and it's unlikely to recharge them fully before the sun goes down, so one stays on Eskom a bit longer for the load, and only Once no solar the eskom charging kicks in. So less cycling in the afternoon.

This is where oversizing the Pv panels would also help me [emoji4] especially in winter.

Thanks for the explanation. Make sense

Sent from my SM-G920F using Tapatalk

Link to comment
Share on other sites

Positives aside, for they are just good. Negatives is where solar bites you.

Over sizing has 2 danger zones:
1) If you exceed the max volts, controller can be destroyed on the spot.
2) If the MPPT operates at +-100% capacity consistently, the heat it can generate can become a problem.

Link to comment
Share on other sites

The only other thing is that even when on solar as a output priority, the power being supplied from panels and batteries during the day can still see-saw, and the DOD on the batteries will be up and down, depending on your varying load, and clouds passing by.

Anouther reason I want a few extra panels to mitigate this effect and try to keep the draw from the batteries as stable/ low as possible.

Link to comment
Share on other sites

Positives aside, for they are just good. Negatives is where solar bites you.

Over sizing has 2 danger zones:

1) If you exceed the max volts, controller can be destroyed on the spot.

2) If the MPPT operates at +-100% capacity consistently, the heat it can generate can become a problem.

What will happen if your batteries is full and you load is half of your solor?

Sent from my SM-G920F using Tapatalk

Link to comment
Share on other sites

Think of the panels as the big kid on the other side of the see saw moving it gently up and down [emoji4] rather than your friend who just jumped off when you were at the top. [emoji4] ouch

[emoji1] [emoji1]

Sent from my SM-G920F using Tapatalk

Link to comment
Share on other sites

4 minutes ago, Arandoza said:

moving it gently up and down

Have you ever seen what happens on a cool sunny day, when clouds move in front of the sun, few minutes later clear sky's again, with the input from the panels? 

Close to that boy jumping off. :D

Link to comment
Share on other sites

What i see on mine is that it only spike let say my load is 500 to 600. I dont get that big spakes if the battery if full.

Sent from my SM-G920F using Tapatalk

Link to comment
Share on other sites

What still konfusses me is when the batteries are full, inverter operating at max the panels and controller can provide so zero goes into / out of batteries as per BMV, yet the batts are not damaged.

 

Link to comment
Share on other sites

Like today. Batteries was full and my load was about 600 when the cloud passes it only went up about 120 to 150w

Sent from my SM-G920F using Tapatalk

Link to comment
Share on other sites

Yes TTT agree. Also it can be that it was late in the day thats why i did not get those big spikes. Maybe around 12 to 1 it will give wat the pv size is?

Sent from my SM-G920F using Tapatalk

Link to comment
Share on other sites

1 minute ago, Manie said:

Maybe around 12 to 1 it will give wat the pv size is?

Depends on SOC of batteries and load powered at the time. If batts need a charge and the load is quite high, the controller will do its best to provide.

It is awesome to see it happen. BMV show a huge drain, few minutes later a huge positive inflow of current to the batts, whilst inverter is just working, and later the SOC is 100%, you see zero going in / out of batts.

Gives you a fuzzy feeling in the stomach seeing it work so flawlessly, in balance.

Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

×
×
  • Create New...