VictorD

Some hopefully useful feedback for you based on my CoJ conversion to prepaid, as well as other's I'm aware of that have done the conversion in my complex:
1) Yes - they didn't have any problem with it.
2) If you have a prepaid meter directly from City Power, then you buy power at those published rates via Internet Banking etc.
3) Not as far as I'm aware - everything has to happen through the customer interface unit (CIU) which has a keypad and talks directly to the meter.
4) Not as far as I'm aware no - also through the customer interface unit.
5) Emails go into a black hole. There are two options - go to your municipal offices yourself, fill out the forms etc., or get a third party to register on your behalf for a fee (I took the latter approach as I didn't have the time or zen-master levels of patience to deal with council - I can provide details via PM).
6) No - I had the same 80A single phase connection.
FYI - the CoJ prepaid meters supplied, at least in Randburg from the Roodepoort CoJ (African Metering Solutions (AMS) CIU-PH04 since about mid 2022) CIU's use power line communication - i.e. the unit has to have a direct connection via your electrical wiring to the meter. Thus, you either need to manually switch the plug circuit you have the CIU connected to (presumably essential load plug) via a changeover switch back to Eskom to be able to load your prepaid vouchers or see you balance, or you need to have a non-essential/grid-connected plug for the meter that is electrically compliantly wired permanently into Eskom. I'm also aware of at least one instance in my complex where the meter was rather picky as to which plug it would reliably work on, so something potentially also to keep in mind.

Hello everyone, I'm intending to install a solar PV system at my property, I started educating myself reading through the forum and learning about volts and amps. It is really a fantastic way to learn and I have already learnt a lot thanks to all the experts and those that recently went through the whole process. I intend asking a lot of dumb questions as I go along in planning my system. 
My first question is around prepaid seeing as it seems to offer the highest return on investment. 
I currently pay R886.98 per month in fixed service & network charges for single phase with an 80A breaker. My monthly use of electricity is around 1200 kWh per month.
My current use since June op to October when the latest CoJ tarifs kicked in, works out to R2.95 per kWh and I worked out that had I been on prepaid, based on the CoJ published rates, that I would have paid R2.52 per kWh and that I would have saved R2,650 in the last 5 months that could have gone towards paying for equipment.
My questions are:
1. Does CoJ allow you to switch to prepaid when you already have a system with panels on the roof that they will see when they come to do an inspection?
2. I based my calculation on the rates below +15% VAT = R2.10 for the first 350 kWh then R2.41 for the next 150 kWh and then R 2.74 above 500 kWh. My question is, is this what you end up paying when you switch to prepaid or do you have to buy electricity through an intermediary ending up more expensive?

3. Is it possible to top up prepaid electricity remotely when you are not at the property or do you physically need to punch in a code on your prepaid meter?
4. Is it possible to see how much prepaid electricity you have left remotely?
5. Can one kickstart the process to switch by email or do you need to physically apply for the switch at their offices.
6. Is the 80 Amp breaker an issue to switch to prepaid? 
Those who have been through this process with CoJ, please assist me with my questions to understand this process better.      

It is very important to select the right size battery cable. A small cable carrying high current will introduce undesirable effects (e.g. DC ripple), cause a fire or serious injury. I strongly suggest you read Wiring Unlimited, a book by Victron Energy on electrical wiring systems.
Ideally your battery cable should be able to carry the inverter full load current without significant voltage drop. Similarly your batteries should be able to provide the inverter full load current. Lastly, your fuse is sized to protect the cable.
If your battery cables are relatively short and not enclosed in conduit on a wall or in trunking then as per BS 7671, you can make do with with 50sq.mm PVC insulated cables with an ampacity rating of 196A @ 70 deg C in free air and a 200A fuse. 

VOC
The open circuit voltage is the maximum voltage that the solar panel can produce with no load on it (i.e. measured with a multimeter across the open ends of the wires attached to the panel ). If two or more panels are wired in series it will be Voc of panel 1 + Voc of panel 2, etc. The voltage is generally highest mid-morning as the sun rises rapidly and the panel temperature is still quite low.
The Voc + approx 3.5 % must be less than the maximum solar voltage permitted by the solar-charge controller. Some controllers shut down if it’s exceeded, while some may continue to operate but the lifespan of the controller could be compromised or it may result in immediate destruction of the charge controller.
ISC
Short-circuit current is the current that flows out of the panel when the positive and negative leads are shorted together. The current can be measured by passing the current through a multimeter configured to measure amps one panel at a time or use a dc clamp meter (this does not harm the panel, but care must be taken to avoid arcing).
The Isc + 20 % is recommended to determine the required current handling capacity of a compatible solar-charge controller. This is the highest current the solar panels will produce under standard test conditions (STC)

And beware of the minus 6 deg expected on Monday in Gauteng - hehehe

Up to a point the inverter will regulate the amount of current it draws from the panels. Even if the panel is capable of say 13A, if the inverter's MPPT input is rated at 11A, then it will not take more than that 11A under normal operation. Any potential power generation that the inverter could have delivered with a 13A current will be simply clipped. A waste for sunny days, but on cloudy days you could get more performance using a higher-current panel.
However, there's more to consider, such as the Isc, the short-circuit current under fault conditions. There's an ultimate limit to the current the inverter can handle. Let's say in this scenario it might be Isc of for argument's sake 15A that is the inverter's limit, while the panel could push out 16A, or even more if you place panels in parallel without considering the consequences. I'm just making up numbers here.
Voc is more clear-cut. You don't want to exceed the rated maximum Voc because the inverter cannot easily regulate Voltage. Take care to leave room to cater also for Voltage spikes due to cold temperatures, or the cloud effect.

Most likely the BMS discharge overcurrent protection is triggered.
What happens when you switch on essentials one at a time? Does the battery hold with minimum load?
I would suggest adding another 2 batteries to make it 3 in total. i.e. 74*3=222A to match the inverter's 8000/48=167A max discharge current.