Modina

I am house renovating and last year I simply wasn't ready with a proper place to mount a system.  Then in January, with the storm of load-sh!tting events, I went into overdrive getting an education and attempted shopping spree.  I spend 2 weeks nearly solid, trying to source equipment.  I'm a electronic engineer, so I understand tech, but I was new to this market and had to pick up the ropes.  THREE times I placed orders with different suppliers and each order failed.  Normally the final purchase price was still pending due to some sort of variable delivery charge, so the order needed to be accepted (by the supplier) and a formal invoice to be sent.  I am still waiting for answers from some of these.  Luckily I never made any payments.

My initial gut told me to go for a 3KVA 24V system.  Every time an order failed, I revisited sites and pricing and reconsidered my options.  A friend said I should rather go for a 48V system.  So at one stage I wanted to place an order for a Kodak 5.48 with ONE Pylontech at Powerforum shop.  I was told the supplier is not willing to sell one battery.  I would at least need to submit a power budget.  Time was ticking.  No example of a power budget was provided.  Communications where slow, taking 2 days turn-a-round.  I moved on and scrapped my 48V idea.

I ended up ordering a clone on Takealot.  A MCE 2.5KW VM II with a 3KW 60-400V MPPT.  I paid R 6200.  A very good price considering the high voltage MPPT.  I then decided on a Hubble AM4 battery.  It is rated at 110Ah with a max discharge of 100A.  Rated at 1C.  Well, at 1C and 110Ah it should actually have a max discharge current of 110A, should it not?  But let's not split hairs.  I order the battery from Liteglo, paid 20K.  I should add that the MCE inverter's status on Takealot altered between sold-out and available multiple times over a period of about 2+ weeks(!)

I intend getting panels later.  Yes, I am concerned of a possible total meltdown of Eskom.  Then I would sit with my finger you-know-where.  Funds are not the problem, but again, my renovation is lagging and I am not really ready for roof dances.  More importantly, I simply do not have the energy to go through another similar purchasing exercise, hitting my head against closed doors.  So I want to take a breather for 3 months and wait for stocks to replenish before I venture into this market again.  I do have a 5KVA gennie to fall back on, in a worst case scenario.  However, the inverter self-consumption (inefficiency) is a problem.  Thus I am a big fan of running as much as possible from 12VDC.

Today, it is NOT about what you WANT but what you can get.  That is my experience.  I could not even get a fuse holder(!)  I looked EVERYWHERE, including Auto electricians.  Later I did manage to order one from Communica.

You need to see what is in STOCK and realise, that even if you phone to confirm, next day the stock might be zero.  I would recommend suppliers that are not dedicated solar system sellers as I think they are more likely to have stock.  I think a solar seller is everyone's obvious first stop.  Also watch out for scheisters out to scam you, as I expect more and more of them will be crawling out of the woodwork in these times.  I see on Gumtree there are some guys asking an absolute fortune for total junk.

When deciding on batteries, make sure that they can handle your required discharge rate, for whatever max power that might be required.  For a 2.5KW inverter you want at least 100A.  And then we haven't even factored in the 10% inverter losses.  Those Mecer Second Life 200A batteries that @Red Falconmentioned, I think, are 0.5C or 100A peak.  If those can be sourced for a good price, do consider them.  Just know that they will not give the full rating of your RCT, Kodak 3.24 or whatever 3KW inverter you decide on.

Victron can be considered the Mercedes of domestic inverters, but like a real Mercedes, there are pros and cons.  Here are a few things you should know:

1. Victron uses different modules to make a system.  So you need more "stuff".  More wires, connectors, etc.  This also needs more time to install.  Other systems normally are single-box solutions.  Your installation could look more like a mad scientist experiment than with other inverters.  😆

2. Victron inverters are referred to as low frequency inverters.  They use 50Hz toroidal output transformers (usually 2 of them) to do the low-to-high voltage step-up.  Most other inverters are "transformerless" designs.  Toroidal transformers are big and HEAVY.  They are also rather expensive, especially if we talk of a few KW.  They give a totally galvanically isolated output which has advantages over the normal inverters that have some DC HV bus connected to the AC output.  Now, toroidal transformers are very efficient but they DO have losses.  I expect about 3%.  This loss needs to be added to the H-bridge switching losses that all inverters, including Victron, use.  So I think that a Victron might have slightly less efficiency.  Oddly enough, the no power idle current on Victron inverters is normally better than other designs.  Victron also has sleep/ power saving modes which other inverters don't have, but I am pretty sure that no Powerforum member would be interested in these modes anyway.

3. Victron make a lot of IP65 rated products.  This has historic reasons due to their origin in the boating/yachting sector.  This means they are 100% water proof.  It also means they are throw-away products.  They cannot be repaired.  The electronics are cast in resin or rubber compound.  The Multipus itself can be opened and repaired.  The MPPT on your list, as far as I know, is potted in rubber.  So the MPPT is not serviceable.  (Go to Youtube and search for Victron MPPT repair and you find a lot of angry people with hacksaws and angle grinders trying to literally only replace a blown fuse.)

4. Victron only keeps spares for 10 years.  Now, I don't have too much of a problem with that per-se, if they would repair down to component level.  I know someone with an old inverter which is considered unrepairable because they cannot source the three PCBs used on that device.  THIS I consider a very, very poor show.  Sometimes, when things go wrong, PCB tracks can get burned and that would require a completely new PCB for a reliable repair.  But mostly, individual components can be replaced.  Either they can't or won't do that - so it seems.  I refer to a specific case I know of in Cape Town.  Perhaps they have some brighter techies up north.  Who knows.

5. Victron normally has no, or very minimalistic user I/O control panels/displays and relies on doing everything via Bluetooth or WiFi.  People like it.  I personally don't.  I think we already have too many devices in our homes that radiate EMF.  But hey, I am a nut case when it comes to that.  So you can scratch out this point.

So if you have the money, go buy yourself some blue bricks. 😀

To me it sounds as if your inverter is not properly earthed, or that multiple earths are used.  You should only have one earth reference, meaning the inverter should use your DB-panel earth.  If your inverter is far removed (maybe in a garage) some people might rather slam  another earth spike into the ground.  There is no guarantee  that one spike might give you a good earth and secondly, it can differ due to ground currents.  I mean physically leakage currents in earth, ground, soil the stuff the Yanks refer to as "dirt".  LOL.    10 or 11V is more than enough for those LEDs to see enough forward current that they turn on dimly.

BTW, with electric fences, it is required to ground the fence energizer using THREE ground pegs, each one a distance of one meter minimum from each other.

I am not an electrician, but a retired electronic engineer.  There seem to be a lot of regulations that I am too stupid to understand or stupid regulations.....  you decide.  For instance, this bull of not combining 230VAC and LV DC in the same conduit.  That is SENSELESS.  But I guess I shouldn't complain.  If you look at US or UK wiring codes, they are 10x more strict.

It is interesting that in Germany, people do NOT need an electrical COC when selling/buying a house.  A COC is only required if/when modifications have been done to the electric system.

The world is turning mad with it's green agenda which is FAKE and I don't buy into it.  Not even solar panels are truely green, due to the exotic input materials and the finite lifetime.  However, now that we are all forced to jump onto this bandwagon, we should COMPLETELY re-write the rule books.  I always smile silently at the people (especially on this forum) that have these mega-installations.  Maybe the owners just have completely non-understanding wives....  that want, no, demand, that EVERYTHING works at the same time.  She wants to boil the kettle, run the washing machine, the micro and the dish-washer all at the same time.

There is no difference between an LCD and a LED TV.  They are both LCD.  But the old model uses CFL backlighting while the LED uses LED backlighting.  LED Backlighting consumes about 30% of what CFL does.  My point is this,  should you not rather throw out your 70W LCD TV and replace it with a similar sized LED TV for R 3000.  A 32-inch LED TV will run at under 20W.  And while you are at it, buy a TV that runs from a 19V laptop-type power supply.  Because then you can buy a R100 Boost converter and feed your TV straight from a 12V battery.  

The TV is just an example.  My point is, people are prepared to spend 150K+ on massive battery banks.  Why not spend only 100K on batteries and use 50K to replace old, inefficient technology.

I think future homes should use AC/DC hybrid wiring systems.  I HATE running an inverter 24/7.  The damn fan noise, the power wastage and the fact that HV AC is detrimental to human health.  OH, now I have blown it.  What a nut-case.  Who is he?  HaHa.  Well, go google the two medical conditions known as MCS (Multi-Chemical Sensitives) and EHS (Electro Hyper Sensitivity).  These two conditions often go together.  Read the story of Canadian song-writer Kim Palmer.  Then maybe, you will understand.

My opinion is that most things should run on LV DC.   12V is not ideal.  24V would be better.  AC distribution should NOT be always on.  Instead, it should be limited to things like vacuum cleaners, irons, power tools, etc. on a demand ONLY supply.  What I mean is, the inverter should be in sleep mode and only power up when a load wants power.  This would be simple to implement.  That's what the battery-backed up LED lights do, just in reverse order.  In fact, you get modules that power down a mains circuit and re-trigger on demand, used by the very people suffering from EHS...

@PsyWulf I don't read or follow any publications anymore.  I have divorced myself from technical stuff.  I refuse to listen to this post-Covid bullshit.  What happened is that a lady I know in Cape Town still is battling with a roof repair before installing a new Victron system.  On hearing that she is still not sorted, I mentioned that with the shitty weather we are having, any solar panels would anyway not produce anything meaningful.  It's then that she forwarded me that link.   I would not be worried about Chinese or Russian propaganda....     @Garthox I didn't even reach so far into the article or webpage, well noticed.  😅  However, it doesn't matter if this is the Fantasy and joke of someone.  With the UN Chief Antonio Guterres saying that we are now in, I quote,  "Global Boiling"  the so-called real news is more fake than the most outlandish fantasy could ever be.

I resign.

Other people will chip in, but here is my take on things.  The hydro generator will have the same problem a petrol generator has.  An unstable 50Hz frequency and fluctuating voltage.  It is ironic that most loads would tolerate that (within reason) but an Axpert and many other type of inverters will not.  Sad but true.  

My believe is that you could run the 230V through a full-wave bridge rectifier followed by a electrolytic smoothing capacitor. This would give you about 320V DC.  This voltage should sit bang in the centre of a high voltage MPPT.

Your 1000 odd watts should be well within the power/input current limit of an Axpert with a high voltage MPPT.

@Coulomb will be very quick to warn us that you cannot do so for high power generators (say 5KVA) as they would be able to source too much current for the MPPT to handle.  I am sure he is right, but I am still scratching my head as to why a very intelligent DSP that is in charge of the MPPT, is not clever enough to self-limit the incoming power.

If the above is not possible, the only other solution would be to bypass the Axpert and charge the battery with a dedicated battery charger.  Getting a 1KW battery charger would be hugely expensive.

PS. A 50A bridge might cost you R 150.  And a high voltage capacitor a bit more.  So this could be implemented at a very reasonable cost.  You would need to mount a heatsink onto the bridge rectifier.

Elektor magazine had a design competition in 1995 and the 1st prize went to a John Dakin who build a 30W wind-powered battery charger using a standard permanent magnet radiator fan motor and a 800mm wooden propeller.  The project was claimed to have cost 20 Pounds (excluding the propeller).

The electronics use cheap, easily available components and there is even a single-sided PCB layout.  I attach the article below.
 
Wind generator battery charger (Elektor).pdf

Your solar panels are likely to contain 3x bypass diodes.  Each diode will have a forward voltage of about 0.6V.  This means that a shaded panel will have 1.8V drop across the three diodes.

Let us assume that during hours of shade you are likely in the morning or late afternoon periods where your solar panels will anyway be down on power.  Let us further assume that your panels will deliver 10A at this time.  This means that the 3 bypass diodes will dissipate 1.8V x 10A = 18W of power.  This power will be stolen from other panels.

If you now connect a whole-panel bypass diode, you would only loose 1x 0.6V x 10A, i.e 6W.  A power saving of 12W.

The diodes are cheap, but you would need extra Y-connectors, cables and the schlep of installing this on your roof.  All that effort to "gain" 12W is not worth it.

The above assumes that the internal bypass diodes are all working OK.  If just one of those diodes would be faulty, you could stand to loose a lot of power.  You could test and replace individual diodes.  This would be quite a mission because you will likely need to remove the panel.  You could also measure the voltage drop across a shaded panel.  If that voltage drop is less than 2V that means all diodes work.  If the voltage drop is much higher you have a problem.  THEN the easiest way to "repair", might be to fit a whole-panel (external) bypass diode.

All this from a guy that doesn't even have solar panels.... 😄  If it was my system, I would wait for dusk and then disconnect the one or two panels that get the shade and use a small 9V or 12V battery with a suitable current limiting resistor (say 1Kohm) to connect over the panel while measuring the panel voltage with a multimeter.  I would hope for a 1.5 to 2 volt reading.

To me it sounds as if your inverter is not properly earthed, or that multiple earths are used.  You should only have one earth reference, meaning the inverter should use your DB-panel earth.  If your inverter is far removed (maybe in a garage) some people might rather slam  another earth spike into the ground.  There is no guarantee  that one spike might give you a good earth and secondly, it can differ due to ground currents.  I mean physically leakage currents in earth, ground, soil the stuff the Yanks refer to as "dirt".  LOL.    10 or 11V is more than enough for those LEDs to see enough forward current that they turn on dimly.

BTW, with electric fences, it is required to ground the fence energizer using THREE ground pegs, each one a distance of one meter minimum from each other.

I am not an electrician, but a retired electronic engineer.  There seem to be a lot of regulations that I am too stupid to understand or stupid regulations.....  you decide.  For instance, this bull of not combining 230VAC and LV DC in the same conduit.  That is SENSELESS.  But I guess I shouldn't complain.  If you look at US or UK wiring codes, they are 10x more strict.

It is interesting that in Germany, people do NOT need an electrical COC when selling/buying a house.  A COC is only required if/when modifications have been done to the electric system.

The world is turning mad with it's green agenda which is FAKE and I don't buy into it.  Not even solar panels are truely green, due to the exotic input materials and the finite lifetime.  However, now that we are all forced to jump onto this bandwagon, we should COMPLETELY re-write the rule books.  I always smile silently at the people (especially on this forum) that have these mega-installations.  Maybe the owners just have completely non-understanding wives....  that want, no, demand, that EVERYTHING works at the same time.  She wants to boil the kettle, run the washing machine, the micro and the dish-washer all at the same time.

There is no difference between an LCD and a LED TV.  They are both LCD.  But the old model uses CFL backlighting while the LED uses LED backlighting.  LED Backlighting consumes about 30% of what CFL does.  My point is this,  should you not rather throw out your 70W LCD TV and replace it with a similar sized LED TV for R 3000.  A 32-inch LED TV will run at under 20W.  And while you are at it, buy a TV that runs from a 19V laptop-type power supply.  Because then you can buy a R100 Boost converter and feed your TV straight from a 12V battery.  

The TV is just an example.  My point is, people are prepared to spend 150K+ on massive battery banks.  Why not spend only 100K on batteries and use 50K to replace old, inefficient technology.

I think future homes should use AC/DC hybrid wiring systems.  I HATE running an inverter 24/7.  The damn fan noise, the power wastage and the fact that HV AC is detrimental to human health.  OH, now I have blown it.  What a nut-case.  Who is he?  HaHa.  Well, go google the two medical conditions known as MCS (Multi-Chemical Sensitives) and EHS (Electro Hyper Sensitivity).  These two conditions often go together.  Read the story of Canadian song-writer Kim Palmer.  Then maybe, you will understand.

My opinion is that most things should run on LV DC.   12V is not ideal.  24V would be better.  AC distribution should NOT be always on.  Instead, it should be limited to things like vacuum cleaners, irons, power tools, etc. on a demand ONLY supply.  What I mean is, the inverter should be in sleep mode and only power up when a load wants power.  This would be simple to implement.  That's what the battery-backed up LED lights do, just in reverse order.  In fact, you get modules that power down a mains circuit and re-trigger on demand, used by the very people suffering from EHS...

with all the rain in cpt these last few weeks I will have loads of power 🤣

I accept there are other products as well but the Victron with models for 65A, 100A and 220A makes for a easy application on inverters. 
I have 2 of the type you mention and yes nothing wrong with it for low power apication or their battery charge control. 
I also like the Victron with cabled remote on/off switch as well as warning before the cut out. 
On these units you don't even need a multimeter as it has a single digit display to guide on the voltage used for cutout. 

It is really no challenge to make a boost inverter that takes 4 or 5VDC and boosts it to 26V or even 56V.  I mean, a typical taser will run from a rechargeable 3.7V and make 12KV or more.  😁     My first statement is not meant to mean that I suggest you build your own, but rather that your MPPT should have no problem boosting a voltage from say 4.5VAC to 26...27VDC required to charge a typical 24V lead-acid battery.  I think your problem is likely to be found with that MPPT.   I realise that wind generators do not have a huge selection of MPPTs available....  MidNite Solar seems to make some decent ones, but I think they are American and will likely cost a fair bit of money.

An alternative would be to buy a buck/boost converter with voltage and current limit adjustment capability and then use that as your battery charger.  You would also need to buy or make your own 3-phase full-wave rectifier but that is cheap and easy.  The only downside is that this setup would not include a turbine brake system, for times that your battery might be full and high winds might cause the turbine to over-rev.  For that you could use a over-voltage protection module which could switch a ballast resistor across the rectifier output at a certain pre-set voltage.

My view is that wind generators are only for very specific applications.  If you are really 100% off-grid in a very remote location.  If you really know how to safe every last watt and you desperately need a backup to a solar panel system.  I personally would first want to get this current system to work and get some experience with using it.  See how much power you can get during a specific season.  Upgrading can be considered at a later stage.  There seem to be a lot of unhappy wind turbine owners that sit with systems that have been completely over-sold and fall far short of power expectations.

This makes little sense.  Why 3x routers?  And why do you power 2x DSTV decoders if you only power one TV.  The first rule in L/S is to reduce your power consumption by as much as you can, especially if using lead-acids. 

Your Telefunken TV is an old LCD.  LCD, by definition, uses cold cathode fluorescent tube backlight technology.  New TVs use LED backlighting.  LED TVs consume approx. 50% less power.  Considering how super cheap a new TV is (in comparison to batteries) it would be a wise choice to replace your primary TV.

You have a 120Ah battery.  Even if the battery is only discharged to 50% SOC, that would mean you would need to replenish 60Ah.  That intelligent charger seems to be a PSA008 - it can charge at a maximum of 8A.  So it would take 60Ah / 8A = 7.5 hours. recharge time.  In reality it is even worse because the battery has losses (converted into heat).  You need to put more than 10Ah in if you want to draw 10Ah.
 

Note that I have no practical experience with wind turbines so accept the following as common sense opinions, some of which could be inaccurate.
 
I am not sure what pickup device you are talking about.  If the 3-phase generator uses permanent magnets there should not be any sensor or controller and the output voltage will likely be a linear function based on rotational speed.

Permanent magnets cost money.  I would expect an alternator to have lower production costs.  Alternators use a field coil that needs to be excited, i.e. it needs power and that can be controlled if desired.  I am in no position to make claims as to what sort of generators / alternators are used.  I don't know the market, but I suspect that permanent magnet generators are likely.  At least this is the impression I get from some youtube channels.

 
I would expect the system to react immediately.  You might be able to remove the blades and then drive the shaft with an electric drill for measurements and determine the output voltage curve.

 
A dirty slipring on a new wind turbine.  Mmm, that doesn't inspire confidence.  1.5 ohms is a substantial resistance.  If you get this setup to work, it might be a good idea to apply some special-purpose grease as those sliprings will not see any action in some sectors, so self-cleaning will be limited.
 
 
No.  The regulator should contain a boost converter and it should start charging at substantially lower input voltage.  I would expect charging to commence at 6 or 7VAC.  At least for a 12V battery.  It sounds as if that MPPT doesn't work properly.  I know you said you have already replaced it....  

If I was in your position I would do some basic tests on the turbine itself, as you appear to already have done.  I would try to spin the turbine at different speeds and plot a basic transfer function of RPM versus output voltage.  With the confidence that the turbine can actually generated a decent voltage, I would hope that it can produce power (i.e. an output voltage under load) and I would first set aside the turbine.

I would then use a bench-top variable power supply - something like 0...30VDC at 1 or 2 amps should be fine, and test the MPPT charger.  I would  connect the PSU to two randomly selected input phases.  Your charger will have a 3-phase rectifier at the input, so it will be safe to connect a DC voltage with any polarity to any of the phases.  With a 12V SLA battery connected on the output of the charger, I would expect charging with an input DC voltage of no more than about 8 to 9V.  Then experiment by increasing the input voltage.  Note that depending on the voltage, battery SOC, etc. your bench-top power supply could/will run out of current and drop it's output voltage.  So a PSU that can output many amps would make for easier testing, but even with only 1 or 2 amps you should be able to confirm basic working of your charger.

If you don't have a bench-top power supply, see if you can borrow one or maybe buy a supply 2nd hand on ebay or whatever. 

Note that I have no practical experience with wind turbines so accept the following as common sense opinions, some of which could be inaccurate.
 
I am not sure what pickup device you are talking about.  If the 3-phase generator uses permanent magnets there should not be any sensor or controller and the output voltage will likely be a linear function based on rotational speed.

Permanent magnets cost money.  I would expect an alternator to have lower production costs.  Alternators use a field coil that needs to be excited, i.e. it needs power and that can be controlled if desired.  I am in no position to make claims as to what sort of generators / alternators are used.  I don't know the market, but I suspect that permanent magnet generators are likely.  At least this is the impression I get from some youtube channels.

 
I would expect the system to react immediately.  You might be able to remove the blades and then drive the shaft with an electric drill for measurements and determine the output voltage curve.

 
A dirty slipring on a new wind turbine.  Mmm, that doesn't inspire confidence.  1.5 ohms is a substantial resistance.  If you get this setup to work, it might be a good idea to apply some special-purpose grease as those sliprings will not see any action in some sectors, so self-cleaning will be limited.
 
 
No.  The regulator should contain a boost converter and it should start charging at substantially lower input voltage.  I would expect charging to commence at 6 or 7VAC.  At least for a 12V battery.  It sounds as if that MPPT doesn't work properly.  I know you said you have already replaced it....  

If I was in your position I would do some basic tests on the turbine itself, as you appear to already have done.  I would try to spin the turbine at different speeds and plot a basic transfer function of RPM versus output voltage.  With the confidence that the turbine can actually generated a decent voltage, I would hope that it can produce power (i.e. an output voltage under load) and I would first set aside the turbine.

I would then use a bench-top variable power supply - something like 0...30VDC at 1 or 2 amps should be fine, and test the MPPT charger.  I would  connect the PSU to two randomly selected input phases.  Your charger will have a 3-phase rectifier at the input, so it will be safe to connect a DC voltage with any polarity to any of the phases.  With a 12V SLA battery connected on the output of the charger, I would expect charging with an input DC voltage of no more than about 8 to 9V.  Then experiment by increasing the input voltage.  Note that depending on the voltage, battery SOC, etc. your bench-top power supply could/will run out of current and drop it's output voltage.  So a PSU that can output many amps would make for easier testing, but even with only 1 or 2 amps you should be able to confirm basic working of your charger.

If you don't have a bench-top power supply, see if you can borrow one or maybe buy a supply 2nd hand on ebay or whatever. 

This makes little sense.  Why 3x routers?  And why do you power 2x DSTV decoders if you only power one TV.  The first rule in L/S is to reduce your power consumption by as much as you can, especially if using lead-acids. 

Your Telefunken TV is an old LCD.  LCD, by definition, uses cold cathode fluorescent tube backlight technology.  New TVs use LED backlighting.  LED TVs consume approx. 50% less power.  Considering how super cheap a new TV is (in comparison to batteries) it would be a wise choice to replace your primary TV.

You have a 120Ah battery.  Even if the battery is only discharged to 50% SOC, that would mean you would need to replenish 60Ah.  That intelligent charger seems to be a PSA008 - it can charge at a maximum of 8A.  So it would take 60Ah / 8A = 7.5 hours. recharge time.  In reality it is even worse because the battery has losses (converted into heat).  You need to put more than 10Ah in if you want to draw 10Ah.
 

What MPPT are you using?   Is it maybe the one below?
There is not much info on this, but it seems to be quite popular for low cost systems.

Thanks, I had done some reading up and checked the maths and ended up changing to the max charge setting in the inverter.

You only tested to about 51 degC.  I presume that the PTC is still rather linear at these low temperatures.  As a PTC is an engineered material with special, purposefully engineered characteristics.  I presume it is made with an exponential transfer function at temperatures over 55 or 60 degC, so that it can self-regulate, if the blurb is to be believed.

So congratulations, you have just prooven Einstein wrong.  You have shown that all that we ever have learned in school and varsity is a lot of fake crap and that we should not "follow" or "believe" in the so-called science.  Especially not the post-Covid science (!)

So let me get back to the 24/7 movie I have been watching - Life in the 21st Century.

I had my heatpump connected to Sonoff cloud with a Sonoff pow, then my internet line went down and I had to make a hotspot on my phone to get the smart switch online so that I can get hot water. The integration should have provided local lan control but it still appeared offline. (I also had the occasional problem where the switch did not trigger for some unexplained reason).
The next day after my internet line was restored I re-flashed tasmota and never had any issues again. For that exact reason I would rather buy hardware that can be reflashed with opensource firmware. 
 

If you charge your battery at 20A you will draw 20A * 25V (nominal) = 500W + a little bit more for some losses.   Your 15A plug can supply 15A * 230V = 3450W.

MCBs have two trip mechanisms.  One magnetic and one thermal.  The magnetic one is instantaneous (well as fast as a mechanical contraption can be) and it will act on a massive over-current.

The thermal trip is intended for loads that are slightly over the rating.  This could take up to a few minutes to trip, depending on how far over the limit the current goes.  Being an electro-mechanical assembly there are tolerances and even the ambient temperature will have an bearing on how long it would take to trip thermally.

You do not want a 5A MCB to trip at 5.5A or even at 7A.  This would trigger nuisance trips due to in-rush currents.  

Correct, but actually much worse.  CBs have B- C- D- curve ratings.  As far as I know domestic CBs in SA are all C-curve (correct me if I am wrong).  A C-curve rated CB will only trip at 5 to 10 times the rated current.  See here: https://www.se.com/au/en/faqs/FA290880/

Here is what you do - an expanded idea based on @Scorp007 fuse idea.

You provide TWO standard outlets EACH being fitted with a 2A fuse.  You tell your visitors NOT to plug in anything more than 300W.  Obviously many will not listen and blow one fuse.  They then have a second plug that still works.  If they still don't get the message and blow the 2nd fuse, then they deserve to sit in the dark.  This way you don't need to come out to your BB every time it trips as there is a backup.  Once your visitors have left, you just check if both fuses are still OK.

Anyone running a heat pump in conjunction with solar water heating? Interest is academic at this stage as I probably use less than 150kWh of power pa (mostly from battery) to boost water temperature first thing in the morning.
Even though I have PV, it still makes no financial sense despite the horrific power price increases of recent times. Similarly I do not believe there is an economic case for a heat pump other than a leaning towards the green brigade.
If we have loadshedding, we have cold water on cold nights unless I remember to choose another timer on the smart geyser switch.

Your solar panels are likely to contain 3x bypass diodes.  Each diode will have a forward voltage of about 0.6V.  This means that a shaded panel will have 1.8V drop across the three diodes.

Let us assume that during hours of shade you are likely in the morning or late afternoon periods where your solar panels will anyway be down on power.  Let us further assume that your panels will deliver 10A at this time.  This means that the 3 bypass diodes will dissipate 1.8V x 10A = 18W of power.  This power will be stolen from other panels.

If you now connect a whole-panel bypass diode, you would only loose 1x 0.6V x 10A, i.e 6W.  A power saving of 12W.

The diodes are cheap, but you would need extra Y-connectors, cables and the schlep of installing this on your roof.  All that effort to "gain" 12W is not worth it.

The above assumes that the internal bypass diodes are all working OK.  If just one of those diodes would be faulty, you could stand to loose a lot of power.  You could test and replace individual diodes.  This would be quite a mission because you will likely need to remove the panel.  You could also measure the voltage drop across a shaded panel.  If that voltage drop is less than 2V that means all diodes work.  If the voltage drop is much higher you have a problem.  THEN the easiest way to "repair", might be to fit a whole-panel (external) bypass diode.

All this from a guy that doesn't even have solar panels.... 😄  If it was my system, I would wait for dusk and then disconnect the one or two panels that get the shade and use a small 9V or 12V battery with a suitable current limiting resistor (say 1Kohm) to connect over the panel while measuring the panel voltage with a multimeter.  I would hope for a 1.5 to 2 volt reading.

Well, at least with the Victron charger, you could switch to Lithium batteries at a later stage.  The small-form-factor Victron chargers are IP65.  That is a good and a bad thing.  They are waterproof which might be handy for something living close to a gate motor?   But IP65 means Victron embedded the electronics is some potting or rubber compound making this charger unserviceable if ever something would go wrong.