Squonk

Thanks for the advice. Now I can go shopping for panels😄

I downloaded the PV string tool yesterday. @Chris HobsonThanks for the nice tool! I just have a question regarding the entry MPPT I max. I notice that you have N/A for the Axpert inverters? What is the reason for that? I have a Mecer SOL-I-AX_5NB inverter - (Axpert MKS II 5K with PVmax 450Vdc). I notice on the sticker on the side (attached) that it states under the heading Solar charger Mode that the Maximum input current = 18A. Do I have to put it into the spreadsheet or is the current limited by the inverter to 18Amps hence the N/A? 18Amps seem ridiculously low as 2 strings will exceed that. Does that mean I can only connect a single string to the inverter? I was hoping to use 2 strings of 5 (or 6) x 405W. My roof area is limited so I have to go for the higher wattage panels. Any suggestions will be appreciated. Axpert MKS II 5K.pdf

I downloaded your tool yesterday. Thanks for the nice tool. I just have a question regarding the entry MPPT I max. I notice that you have N/A for the Axpert inverters? What is the reason for that? I have a Mecer SOL-I-AX_5NB inverter - (Axpert MKS II 5K with PVmax 450Vdc). I notice on the sticker on the side that it states under the heading Solar charger Mode that the Maximim input current = 18A. Do I have to put it into the spreadsheet or is the current limited by the inverter to 18Amps hence the N/A? 18Amps seem ridiculously low as 2 strings will exceed that. Does that mean I can only connect a single string to the inverter? I was hoping to use 2 strings of 5 (or 6) x 405W. My roof area is limited so I have to go for the higher wattage panels. Any suggestions will be appreciated.

What charge controller would you use with the battery charger?

Thanks for the info. Can you think of an inverter that separates the inputs? If I look at the block diagram of the Quatro it shows multiple ac inputs. Would that also be connected together inside the box?

As I mentioned I would have to do that "illegally" if I do not register with the council. I would have to disconnect the PV arrays then maybe they will accept it as a UPS

@ Sidewinder Yes, I suppose I can automate the whole process but it will probably cost too much to justify. Your suggestion of a generator made me think. Can I not connect AC from the grid to the generator input via a contactor that kicks in when PV power reaches a certain level. I just wonder if the generator input on inverters (for instance an Axpert) is connected straight to the mains input or is there a change over switch between the 2 inputs. I also assume a inverter with grid feedback capability will never feed back on the generator input. Maybe one of the gurus on the forum have an opinion on this?

Thanks for the advice. Problem is , as soon as I connect an inverter to the grid ( any inverter) the municipality requires me to go to a two part tariff which has a fixed monthly cost of R310. I will then pay 40c less per unit but the it will still be way more expensive, unless I can feed back a lot of units into the grid. Problem is with the maximum allowed inverter size of 3.6 kVA I will probably struggle to generate enough units for self consumption. Apart from that I have to add a compulsory bidirectional prepaid meter cost (R16k) ,professional engineering fees and the hassle of the the onerous registration process. Not worth it in my opinion. That is why I want to stay off grid. I have installed two DB section splitting the house into a PV supplied section and a grid supplied section for the heavy consumption items. I just want to be able to charge the batteries if there is no PV available and I reach min SOC on the battery pack. I cannot charge it with the inverter, unless I connect a generator to it, as Sidewinder suggested, but prefer to use an AC charger. I suppose I can stealthily connect the inverter to the grid with a plug as some forum members have suggested but I would like to keep it completely separate for legal reasons. So the question remains: What ac charger can I use the charge the Pylontech batteries . From what you mentioned in your reply a 25A charger which can be adjusted to 52- 54V should be able to do it. I have read somewhere on the forum that the BMS will protect the batteries and shut down if needed if it detects overcharging no matter what other devices (ICC/ESS or inverter) tell it to do. I managed to get hold of a Pylontech inverter compatibility list so I will stick to that when I purchase . It only has inverters on the list however, no MPPT chargers

Good day to all. I am just getting into solar PV this so please excuse my ignorance. I have a couple of questions for the experts! Can I get some suggestions about what AC battery charger will be suitable to charge a 2.4kWh Pylontech battery setup? Can you have have 2 chargers connected to the battery set at the same time? i.e. Inverter/ MPPT SCC and an AC charger? I am planning on putting in an off grid system but would like to be able to charge the batteries if PV power is not available without connecting the PV inverter to the grid ie. hybrid inverter setup . I do not want to go grid tied due to the ridiculous municipal costs. Does anybody have a list of inverter/ MPPT models or brands that are compatible with Pylontech (or other Li batterries). I cannot find a website for the Pylontech that actually specifies the requirements for suitable inverters and MPPT's. How do you determine the voltage and current charging requirements for a battery? Do you have to match the charger output specifications exactly to the battery set or can you use a larger or smaller charger? Any answers will be greatly appreciated.

@ Erastus Have you received permission to be a net producer? In Mossel Bay your are not allowed to be a net producer of electricity so you cannot use the grid as a battery. Also, they seem to be quite strict on the 3.5 kVA maximum size for domestic installations.

I plan to have the PV supplied section of the DB completely "off grid" . If I have no PV or battery power available I will manually switch over to grid completely isolating the inverter etc. That way I can at least install a 5 kVA inverter system. If I go grid tied they limit you to 3.5 kVA. I suppose I can automate the "switch-over" at a later stage.

From what I can gather they do not accept "built -in software selectable reverse power blocking" They do not even have any Victron equipment on their Approved List!

That means connecting the inverter directly to the grid and I will have to go through all the onerous and costly procedures to comply with Mun regulations. 4 quadrant meter, professional engineer sign off and commissioning report etc. I am not sure whether that is worth it if I cannot generate enough kWh to feed in to offset the expenditure

No, you have to install a bi-directional split meter (credit meter) if you want to go grid tied with the option to feed in . Other wise if you go grid tied without the option to feed in you can keep the prepaid meter but you have to install a "Reverse Power Blocking" device

Just a quick report back: I got the SSEG application forms and Tariff structure from Mossel Bay Municipality. Turns out their strategy is very similar to CoC .... to make it completely unprofitable to go grid tied. They have a basic fixed network charge of R308 /month and energy consumption charge of R1.44 per kWh. The energy feed in rate is R0.44 /kWh. The maximum inverter size for a 60A grid connection is 3.5 kVA. So, and please correct me if I am wrong, you will have to feed in 700 kWh/month (22,5 kWh /day) to offset the basic network charge. Problem is with a maximum allowed 3.75 kVA inverter system you will never achieve that, even if you have zero self consumption. I do not understand the logic behind the tariff structure at all unless it is designed to discourage grid tied domestic installations. I will therefore go the "partly off grid" route. Split the DB and have one section "on grid" and the other section "off grid" (with the option to switch over to grid as the need arises). THe generation side will remain isolated from the grid to keep the authorities happy. At least I will be able to put in a > 3.5 kVA inverter to provide sufficient kWh. I would like to have a system capable of generating about 10 kWh / day I will appreciate your advice regarding the topology of such a system. I have listed two possible topologies : 1. PV Panels - separate MPPT - Pylontech Batteries - Inverter. 2. PV Panels - combined Inverter MPPT (Axpert?) - Pylontech Batteries - similar to your system ? @Chris Hobson Do I need an additional Battery Management device or will the Pylontech BM system be sufficient?