I got very good advice on the general forum but I am still somewhat uncertain as to what exactly the Axpert will do for me.

As to whether it will provide PV power blended into the mains supply on the dedicated circuit on which it operates Coulomb says:

. . . I would describe it as the Axpert using PV power first, battery power second. However, if the load on that circuit exceeds what the inverter can supply, then the entire load switches over to AC-in (if available), and PV power only charges the battery (unless full).

Sorry my ignorance.  Assuming a constant mains supply, does that mean the batteries start providing power when the sun sets?

What I need is a system where the mains operate whenever there is a supply, the panels blend in and the batteries are left undisturbed (other than a slight top up from time to time). The batteries should only provide power if there is a mains failure. So after sunset the mains supply me. During the day also but if it is sunny I get some use out my panels. And if there is a mains failure the batteries start working.  

Is that possible?

Coulomb:

So really, the main place that the Axpert falls behind as far as usage of solar power is concerned is when it is in line mode. [emphasis provided]

What does that mean? When and how does it get into that mode and what other mode is available?

 

Perhaps someone can refer me to a source where I can read a bit about the axpert without troubling Coulomb et al??

 

regards

Hi Clivan, The axpert 5kva Mk11 does exactly what you want. It will use available pv and add to that grid power still required or battery power if the grid is not available.

 

Edited April 19, 20197 yr by Chris-R

OK how do I know what axpert i bought?  It is a SOL-I-AX-5p

When I google I get this:  Axpert HYBRID 5000VA / 5000W Inverter Charger 4000W MPPT 48v (SOL-I-AX-5P)

 

Is that the one?

 

I also got a much smaller unit for an outside cottage - 1.5kva/1200 watt.  Can that one do it? How do I set it up to do what I want?

 

I think it comes back to my main questions - the bothersome issue about ignorance

ahh ... @Clivevan, you certainly joined the right forum... i was n your shoes a few months ago  

While i am not that clued up on everything i can tell you that going through the specs of each component you bought closely then highlight things you don't understand and ask it here.  Broad questions usually gets answered in detail, but not understanding the detail makes a "whoosh" sound as it goes over your head  

Start like this:

1. Why do i want solar?
   1. Will give you an idea of which way to go. Grid tied if you want to save money, Off-grid if you want to be self sustained
2. How much power do i use?
   1. Gives you an indication of how many KwH you will need to accommodate
3. Will i do the install myself?
   1. Doing a self install will probably save you quite a bit, but the rabbit hole is quite deep, and just as much fun as Alice portrays 
4. What components are required
   1. Based on question one and two above you can start figuring out what equipment you need (base equipment, like inverters, chargers, pv modules, batteries etc.) 

Once you have those four questions answered then its down to the nitty gritty, like equipment specs, wire thickness, connectors, fuses and the lot.

I know i just wrote a lot without answering any questions, i wish i could, but i am still a noob  

Edited April 19, 20197 yr by stoic

On 2019/04/20 at 1:51 AM, Clivevan said:

Sorry my ignorance.  Assuming a constant mains supply, does that mean the batteries start providing power when the sun sets?

That depends on the settings, particularly the Output Source Priority setting, setting 01. If you choose SOL for that setting, yes it switches to line mode (= bypass mode on this model, utility provides all the load power) immediately after sunset. It will even top up your battery with utility power if the PVs didn't get them full at the end of the day.

Quote

What I need is a system where the mains operate whenever there is a supply, the panels blend in and the batteries are left undisturbed (other than a slight top up from time to time).

You can also do exactly that, with the UtI (Utility first) Output Source Priority setting. But then, you'll get almost no value from your panels. To get value from your panels, you probably want SOL Output Source Priority, so the inverter switches to battery mode during the day, with the PV panels charging the battery and keeping it full. That means there is a risk of losing mains when the battery is low near the end of a rainy day, but you can tell the inverter to switch to line/bypass mode at a fairly high voltage, so the battery never gets all that low even if PV production is terrible. This is controlled by settings 12 and 13, "back to utility" and "back to battery" settings. You'd probably want to set setting 13 to "FUL", meaning if the battery needs to be recharged during the day, then it won't go back to battery mode until the battery is completely full. When the battery is charging during the day, it will use a combination of utility and any available PV power, and the loads will be powered by the utility only.

Quote

The batteries should only provide power if there is a mains failure.

This is the closest that you can get, without a hybrid inverter. [ Edit: or wasting your PV panels. ]

Quote

So after sunset the mains supply me. During the day also but if it is sunny I get some use out my panels. And if there is a mains failure the batteries start working. 

You'll get all the above with SOL Output Source Priority.

Quote

 Coulomb:

So really, the main place that the Axpert falls behind as far as usage of solar power is concerned is when it is in line mode. [emphasis provided]

What does that mean? When and how does it get into that mode and what other mode is available?

The inverter has half a dozen modes, but most of them are unusual, like fault mode or start-up mode. The two main modes are battery mode and line mode.

In battery mode, the battery supplies all the loads, but any PV power is available to charge the battery. When the battery is full, effectively the loads are supplied entirely via PV power, if there is enough. Any shortfall comes from the battery, to be replaced once the PV power exceeds loads again. If you have enough PV panels for the load, then this will hardly bother the battery at all; it will stay above about 95% SOC (note: the SOC display on the Axperts is terrible, especially with LFP batteries; for lead acid batteries, it's quite rough). In battery mode, utility charging is not possible.

In line mode, some relays come into play and the AC-out is connected to AC-in. In your situation, this means the loads will be powered by the utility. In this mode, the utility charger is available, and PV can charge the battery as well. The battery will not discharge at all in this mode, except for some losses (perhaps 35 W).

When to switch between these two major modes is a fairly complex decision. Obviously, if Eskom drops out, the inverter will immediately switch to battery mode. With the SOL Output Source Priority, the inverter will switch to line mode when PV is not available (i.e. at night, or if you switch off the PV isolator). Whenever it is in battery mode, it will switch to line mode if the battery voltage drops below setting 12 (the Back to Utility voltage), assuming that AC-in is present. When in line mode, it may consider switching to battery mode (during the day in the case of the SOL Output Source Priority) if the battery voltage exceeds setting 13 (the Back to Battery setting). Setting 13 is either a battery voltage, or the special setting FUL; the latter means when the battery is fully charged, and the charger switches from absorb stage to float stage.

On 2019/04/20 at 1:51 AM, Clivevan said:

Perhaps someone can refer me to a source where I can read a bit about the axpert without troubling Coulomb et al??

You might get some extra feel for how it works by reading the user manual. The one from MPP Solar for the PIP-5048MS model doesn't require registration for downloading: 

• PIP-MS 1-5KVA manual-20190109.pdf

Edited May 14, 20197 yr by Coulomb
"fairly complex operation" → "fairly complex decision"

TX Coulomb and all - I am busy reading and learning.

Stoic your questions are very pertinent - but I think I have passed that point (perhaps).  See if you think I need to give more consideration to anything (often a newly qualified axpert expert has better insight into the mind of the newby):

 

Your first question:

1. Why do i want solar?
   1. . . . . Grid tied if you want to save money, Off-grid if you want to be self sustained

Neither - I do not believe I can save much money grid tied.  And off-grid is even worse money wise.   So just load shedding.

BUT it would be nice to be able to survive an extended load shed. Then I need panels.  Enough to charge the batteries. And not to have them totally wasted  (standing idle most of the time between extended loadsheds), it  will be nice if I can switch them into my main DB for average days (average electricity days that is ie mains are working) So grid tied in this limited sense. But much more important for me to determine and cater for an "essential" load.

 

 How much power do i use?

1. Gives you an indication of how many KwH you will need to accommodate

 

Base load in my house is  max 500 watts during the day.  But much less if I only use the essential load. Some evenings essential load may reach 750 watts.  During any load shed I cope easily with 750 watts (max and only if the load shed coincide with 5.30 pm to 9.30 pm. Otherwise my essential load is no more than 400 watts)  I have town gas for home heaters, geysers and stove.  So a 5kva axpert with 4 x180 amp omni batteries should be ample.  Not sure what else I need - battery equaliser or some such item? separate small DB?  switches and fuses? cabling?  I also require a slight rewire from my DB but my electrician will do. Using the batteries basically ONLY during load shed and never drain below 60% (that is using 40% DOD thus 60%?) and even that DOD only VERY very rarely when load shed coincides with evening hours or someone makes a mistake or something. In this way I hope my batteries will last 5 years.  rEalistic?

But spikes are nevertheless enormous - every now and then may reach 15000 watts and during winter office hours are a constant 8000 watts (without counting spikes) Problem is an outside office where electricity is still used the old fashioned way.  And an outside laundry. Before I even think of comprehensive grid tie I need to get rid of the electric heaters in the outside office area. And some.

1. Will i do the install myself?
   1. Doing a self install will probably save you quite a bit, but the rabbit hole is quite deep, and just as much fun as Alice portrays 

My house I will leave to an expert.  And watch closely and ask questions. I am also doing a small outside flat.  Its base load mostly zero.  Sometimes the essential load reaches 300 watts (1 PC and TV).  Can survive load shed with 3 kva axpert and x2 180 amp batteries. Will see if between my electrician and I we can do the job once the house is done and with a bit of advice from the installer.

1. What components are required
   1. Based on question one and two above you can start figuring out what equipment you need (base equipment, like inverters, chargers, pv modules, batteries etc.) 

I tried to answer that above. But please PLEASE add whatever value you are willing to assist with!!