Basil Katakuzinos

I'm not an expert in this, but here is my 2¢ worth.
An MPPT is designed with PV panels in mind, obviously. One of the characteristics of PV panels is that as you load them more, their voltage drops and you get a smooth increase in power. Load them less, and the voltage springs back. But the critical thing is that you gradually get more power as you put more load on. If you like, the panels have a relatively high internal resistance. You can short circuit them, and the current will be quite limited; Isc for any panel is only a little larger then Imp.
I don't know much about hydrogenerators, but it seems to me that they would be more like an electric motor/generator. An electric motor has a quite low internal resistance, and short circuiting the output of a motor will generally result in damaging current levels. Though maybe if the mechanical input is weak (I imagine that peleton wheels are pretty weak for example), maybe you can get it to look more like a PV panel than a motor.
My concern is that the solar MPPT will adjust its PWM ratio, effectively adjusting the "back EMF" of the PV input by a small amount, but this small change in back-emf will generate a large change in current, because you have two voltage sources connected by a small internal resistance.
Motor controllers deal with this issue, so it can be handled, but my concern is that you may need a rather different design than a standard solar MPPT. Motor controllers operate over small time scales using the inductance of the motor windings to limit the current. Once you convert the generator output to DC, you can't use that technique. I think what you want is effectively a motor controller, and to draw power from the generator smoothly, you'd to the same thing that your electric car does when it regenerates and pushes power into the battery. In this application, you don't have use for what is normally forward power flow: battery to motor, as that would use energy to make the stream flow faster.
But a motor controller is a very different beast to a solar MPPT. For one thing, the motor controller is three phase.
A wind generator's charge controller would possibly be the closest off-the-shelf thing that might work in this application. You could presumably connect such a thing directly to the inverter's battery. The speed might be all wrong; I imagine that wind turbines spin at much slower speeds than a generator. You might be able to overcome that with mechanical gearing.
I hope that this makes some sense.
You really need to find someone with expertise in this area. I'm not that person.

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.

My son has a strong stream of water coming down the mountains (head; over 150m) 24/7.    To start as an experiment he is considering installing a small hydroelectric 1000w 220v generator and store energy in 4x 105ah gel batteries.
Can he connect this generator to a simple 5kva Axpert and use it's MPPT to charge 4 batteries?  (he has a surplus Axpert) In view of the fact that this generator will run 24/7,  will it take the batteries to SOC of 100% via the Axpert (assuming that due to the amount of water and the head a max output of 800 - 1000w will be possible)? As far as I can remember the Axpert doesn't have a generator input, can he just use the AC input?

A very good point. 
Now there are cases where 2 friends bought the same inverter. One using a S-100 and one a Revov. After a week the guy with Revov found his inverter will not switch on. Some tests were done and both inverters were fine coupled to the S-100 or a lead acid battery. 
Surely the manufacturers can sort this out as it was sold as a compatible bundle. 

Please... just dont do this(But if you do, i actually would be very curious to see this system in action). I do though feel like this solution, just like the water after filtration will turn out to be rather...shitty. 

Update:
Changed the wiring as suggested - big storms etc last night and so far so good... Will let you guys know in a bout a week if all is good.
Wired like this now:
eskom >>> main breaker >>> inverter >>> earth leakage a >>> essential loads eskom >>> main breaker >>> earth leakage b>>> non essential loads Thanks for the input and assistance.
 

Is your inverter protected by this earth leakage (eskom >>> earth leakage >>> inverter), if this is the case then this may be your problem. 
It is recommended to not have your inverter protected by earth leakage but to only have the loads protected. so your power should flow as follows 
 
eskom >>> main breaker >>> inverter >>> earth leakage a >>> essential loads eskom >>> main breaker >>> earth leakage b>>> non essential loads where earth leakage a and b are two separate breakers. 
 
PS. I have not included some protection devices (like MCB's) above as the above example is just to show where the earth leakage should be placed.
PPS. My system has the solar earth and AC mains earth connected to the same grounding rod, though I do not have the experience to say with confidence that this is the correct and best practice method. 
 
Edit: On second thought, I feel confident enough to say that your inverter should not be fed from earth leakage, here is a quote from Victron Wiring unlimited
"An RCD must be mounted before the loads in an electrical installation. In reality this means that the RCDs have to be mounted before the installation is split up into different groups. If an inverter or inverter/charger is used, the RCD should come after this, otherwise there will be no earth protection while the inverter is operational. Consumers that are only operational when connected to shore power will need their own RCD."
 

Hi Douw
As a registered electrician I have a dedicated earth leakage tester.
I have replaced numerous earth leakage circuit breakers that only trip when there are electrical storms normally the old Heinemann brand.
I agree with the other comments that you must connect the earth leakage after the inverter.

I feel like this could possibly be a communication problem between the BMS and the inverter. Surely this is alphas problem to solve considdering they replaced the inverter.

Just as an aside, Richard is our resident DC proponent. He is right that it is often a lot more efficient to run things from DC rather than round trip it upwards to 230VAC just to drop it back down again to 12VDC later.
I take a more practical approach, which is that if an inverter is required in any case (because I have a load that won't have it any other way), then the extra troubles of converting things to DC, getting alternative power supplies for them (where needed, of course that won't be needed everywhere), transmission losses over longer distances, DC-rated switches and so forth, may well mean that you swallow the inefficiency and just stick with AC.
You also cannot run AC and DC in the same raceways, which means new conduit if there's going to be wiring done. Finally it makes it a lot harder to convert the house back to "standard" if you ever decide to sell it.
Of course none of what I have just written addresses your main problem: That buying 12V equipment in the shop isn't as easy as it used to be. So you either need a supplier, or some DIY.
For your intended use case, which seems to be contained to the garden-area, going with 12V is doable and will save costs on an inverter.

Remember the Inverter does not have to reside next to the DB board if you have the necessary ducting in place.  This is normally only done to avoid running cables through existing spaces.
Therefore your no1 priority is to ensure you have identified the Inverter location and provision the necessary ducting to;
Main DB board, PV Roofing feeds to all arrays Earthing facilities (may be external spike) Possible Generator AUX feed (future) etc. I have three DB boards in the house, yet installed Inverter and its own DB's in garage with underground feeds to main house DB.
Then some other criteria to manage are;
Enough space for inverter and batteries (wall or cabinet) with sufficient ventilation (If on back wall of garage) two cars arrive home - hot engines - increases env temperature The noise of cooling fans (already mentioned by Milan188). Appearance - as you mention avoid using walls such as entrance for cable feeds Lastly ensure you have space for expansion - additional batteries, etc. You never have enough (overcast days) and if Eskom does not turn things around, you'll need the extra. Good luck and enjoy!
 

Isn't the house a bit small?
Where will you sleep?
 
🤪

I would make space to add it in the bottom left corner of the garage near the garage opening. 
The reason for this is fan noise from the inverter won't be as loud for people in the kitchen and the cabling for the solar will be easier because you can just drill through the left side wall of the garage. 

Trade in the 5kW inverter for an 8kW inverter, connect both strings in parallel into one MPPT (9S-2P), and get another 18x330W panels and do the same for the next MPPT.
This way depending on your base load, even with overcast weather you can run the house and charge batteries. Another battery is always a welcome addition, if Eskom blows a transformer in the area.

I am having a borehole installed to share with some neighbors. 
The installer has placed a pressure tank on the system that feeds water from the borehole to each house. 
When this water arrives at my property i will have a tank to store water and a filtration system. The installer insists that I do not need a pressure tank for the system in my house, is that true? 
 
Also here is a screenshot of the parts he has quoted me. 

 
Also I am considering changing out the pump he has quoted me for a 1.5Kw JoJo branded VSD Pump as it is much more affordable.

Just keep in mind that the sunsynk can not charge from the AC inverter when no grid is available. It is not an Inverter/Charger but rather a bidirectional inverter, it can not invert and charge at the same time. 
Furthermore placing a 50KW ac inverter onto a 12Kw off grid inverter may lead to instability in the grid I believe this is why Victron for example requires your AC Coupled inverters to not exceeded the KVA rating of your hybrid inverter. The hybrid inverter has to regulate the grid and with a 50Kw AC inverter it may fail to do this effectively. 
Also Keith from sunsynk advises that AC Coupled inverters should be placed onto the Gen Port and not the load.... this may be a problem for you also as I would not put 50Kw through the Gen port of a 12Kw sunsynk.
Have you considered looking at an SMA system for this, they offer much more scalable systems and specialize in AC Coupled solar? 
Is it within the budget to parallel 3 sunsynks

Please... just dont do this(But if you do, i actually would be very curious to see this system in action). I do though feel like this solution, just like the water after filtration will turn out to be rather...shitty. 

My personal favorite choice. I have avoided Gas cookers because that just means im paying for gas which works out more expensive than using a traditional electric stove top.
Maybe im incorrect on this though.

I have a Kodak 7,2 Kw off-grid inverter. 

Fantastic, thank you very much for confirming. 👍

Total newby here with next to zero knowledge of any form of electrical systems.
What I have:
7.2 Kw inverter 5.1 Kw lithium iron battery 1620 W of solar panels Typically the solar panels will supply (on a sunny day, of course) between 30 and 40-something % percent the active power used by the house. Example right now: House usage at present is 218 W, input from panels is 99 W. The battery is fully charged (and priority is set to 1=solar 2=grid and 3=battery). 
My question is: should the solar panels not provide a figure closer to 100% of the active power usage (assuming enough sunlight available)?
Thanks in advance. 

My spelling is terrible ... on other forums I rely on Grammarly to fix my writing, but it doens't seem to work on powerforum. Would it be possible to somehow enable it? 

I've got the ja 540w installed. The installers didn't have an issue with them. 

they're very bulky and heavy for one person to handle, mine were 465w however.
2 people makes it much easier.
in my case I have a landrover with a heavy duty 4x4 roof rack which can handle a lot of weight safely, and simply got my supplier to load onto the roof. (only a 15 min drive back)
back home, line up with the carport and instant roof level panel unloading, no mess no fuss. 
having done it as 1 person, I can really say its not for the faint hearted, rather get a friend in.
 

1. Usually metal fittings will have a screw where you put the earth terminal, if you take a picture of both sides I'll point it out.
2. It is likely complaint yes.  Many people recommend many things. The most recently are Waco connectors.  But in terms of low resistance connection the lowest cost high quality part that has been in use forever are wire nuts.  You twist wires together and then turn the wire nut on.  Do not put more than 3 wires at a time into a wire nut.