50 minutes ago, Sc00bs said:

I have a pool heater for my excess power :-) 

I am currently running 4 x 6.4kw BSL Batteries, the current to them in/out is limited to a max of 160A (+-8kw) purely because of the cabling. 

Apologies on the pricing, I went and had a look at the results when I googled it for the latest pricing and that site definitely looks like a scam site. Going price does seem to be around R54k

I currently have 3 strings on my inverter 

MPPT1 - West Facing 16 x 455W JA Solar in 2P8S configuration  Max Amperage 24.1A (Isc 10.56A) 7,255w (7280W of panels)

MPPT2 - East Facing 12 x 455W JA Solar in 2S6P configuration Max Amperage 23.7A (Isc 10.56A) 5,522w (5460W of panels)

MPPT3 - North Facing 8 x 555W Jinko Solar  (will probably upgrade to 10)  Max Amperage seen 16.5A (Isc 14.07A) 5,048w (4440w of panels) 

I have read documents on the mixing of a parallel string between East & West facing panels, so in a 16 panel 2S8P config, one of the halves facing East and one facing West. It is not first prize and can be done, I would suggest running one MPPT only facing East, One facing only West and the split the last one between East/West and see how it compares in production, would be super interesting.   

 

Another thing for you to consider 🙂 

I did notice in my investigations that there is also a High Voltage 20kw 3-phase DEYE for R48k from Solar Warehouse. 

 

It has 2 x MPPT's but supports up to 850V per string so you could run 16 panels on one MPPT East Facing  and 16 panels on the West Facing MPPT

You will need high voltage batteries but High Voltage is definitely the way things are going so would be worth looking at.  

 

Although 3 ph seems good and going 3 ph a number of supply authorities are much against providing it for normal household use. Also cost is normally higher. 

1 minute ago, Scorp007 said:

Although 3 ph seems good and going 3 ph a number of supply authorities are much against providing it for normal household use. Also cost is normally higher. 

Hi @Scorp007  I thought he already has a 3-phase supply, I also noticed that the HV 3-Phase inverter allow for a 100% unbalanced load which is pretty handy.  Price on it is super good as well although I think that he might have to cough for the batteries as the HV ones seem to be quite expensive still. 

6 minutes ago, Sc00bs said:

Hi @Scorp007  I thought he already has a 3-phase supply, I also noticed that the HV 3-Phase inverter allow for a 100% unbalanced load which is pretty handy.  Price on it is super good as well although I think that he might have to cough for the batteries as the HV ones seem to be quite expensive still. 

Based on the specs of the inverter posted 6 hrs ago it was for a 12kW 1 ph.

1 hour ago, Sc00bs said:

I am currently running 4 x 6.4kw BSL Batteries, the current to them in/out is limited to a max of 160A (+-8kw) purely because of the cabling. 

Scheepers. Am I reading 8000 cycles right? Had not seen these before. Interesting.

1 hour ago, Sc00bs said:

Apologies on the pricing, I went and had a look at the results when I googled it for the latest pricing and that site definitely looks like a scam site. Going price does seem to be around R54k

All good, just wanted to make sure I wasn't missing something.

3 hours ago, Scorp007 said:

The voltage does not really increase much during the day. As long as there is strong light like even on a cloudy day the volts will still be high. With shade and clouds it is the amps that cannot be generated by each cell. 

As mentioned before you will see on the panel specs at what irradiation the panel output is given. It is under an ideal 1000W/m². The average during summer in Gauteng is around 800W/m². However when there is cloud edge you might even exceed 1000 but only for seconds. This is part due to panels cooling down during the period when the sun is behind a cloud and also increased irradiation. 

For 13A panels (Imp) you are lucky if you see more than about 11.5A. 

Ok, so this is exactly what I wanted to know... the voltage is the more or less constant one, and the amperage will be the one to shift around.

 

33 minutes ago, Sc00bs said:

Hi @Scorp007  I thought he already has a 3-phase supply, I also noticed that the HV 3-Phase inverter allow for a 100% unbalanced load which is pretty handy.  Price on it is super good as well although I think that he might have to cough for the batteries as the HV ones seem to be quite expensive still. 

 

25 minutes ago, Scorp007 said:

Based on the specs of the inverter posted 6 hrs ago it was for a 12kW 1 ph.

Yeah, I'm on single phase, with a 60Amp breaker.

1 minute ago, display_Name said:

Ok, so this is exactly what I wanted to know... the voltage is the more or less constant one, and the amperage will be the one to shift around.

 

Just my input on the cycles. Some  manufacturers would give you cycles based on 50, 80 and 100% DOD. With these levels you will find at 50% about 7500 cycles. At 80% about 5500 cycles etc

It is important to understand that the battery cells do not generally stop working but rather have a gradual reduction in capacity (unless there is a faulty cell obviously).

Warranties usually guarantee a specified capacity after a specified number of cycles.  

 

The main factors which affect battery life in Lifepo4 battery cells are: 

Depth of discharge - 80% seems to be a good trade of between cycles and capacity usage, the higher the DOD the less number of cycles the batteries will do. 

Rate of discharge - the faster the batteries are charged and discharged the lower the number of cycles you will get out of them. 

 

4 hours ago, Sc00bs said:

It is important to understand that the battery cells do not generally stop working but rather have a gradual reduction in capacity (unless there is a faulty cell obviously).

Warranties usually guarantee a specified capacity after a specified number of cycles.  

 

The main factors which affect battery life in Lifepo4 battery cells are: 

Depth of discharge - 80% seems to be a good trade of between cycles and capacity usage, the higher the DOD the less number of cycles the batteries will do. 

Rate of discharge - the faster the batteries are charged and discharged the lower the number of cycles you will get out of them. 

 

From this graph 50% at 1C gives 18 000.

80% gives 4 500.

From one of our best local manufacturers of lithium building batteries for over 10yrs the following cycles are provided. I know which one I would use for estimation. 

 

1 hour ago, Scorp007 said:

I know which one I would use for estimation

When you size a battery for a full 24 hour period without charge, and a depth of discharge of 80%, you rarely get to 80% DoD if you generally get your daily solar. 

4 hours ago, TaliaB said:

When you size a battery for a full 24 hour period without charge, and a depth of discharge of 80%, you rarely get to 80% DoD if you generally get your daily solar. 

May be I used the wrong words. I was talking of estimating the number of life cycles for a battery. Thus as you say one school will hardly get to 80% DOD and the other school will discharge so deep that the battery BMS cuts out. We regularly see questions around how to wake up a lithium. 

On another forum I see a guy who nearly every 2 weeks have to wake up 1 or more batteries. 

Ok, finally pressing go on the install after being away for a bit. I'm sorted with Panels (28 x 55W Jinko Tiger), Inverter (Sunsynk 12kW single Phase), Installer and Installation.

Last thing I'm wrapping my head around is still the battery. I'm currently thinking that a Volta Stage 4 battery will suit my needs and is definitely cost effective (current quote is R53,200 which is about R6000 cheaper than the SolarMd 4143). I was quite keen on SolarMD, but no I'm not sure that it's worth it unless I'm going to walk into issues with the Volta.

However, from a technical specs perspective (https://voltaenergy.co.za/volta-series-s/), what is the kW output I can get from the Volta? Is it 200A x 44.8V (Discharge Cut-Off Voltage) / 1000 = 8.96kW? I assume that I'd use the Discharge cut-off voltage as the max voltage... and this leaves it with only 9kW peak output, which is less than the 10kW of the SolarMD?

8 hours ago, display_Name said:

However, from a technical specs perspective (https://voltaenergy.co.za/volta-series-s/), what is the kW output I can get from the Volta? Is it 200A x 44.8V (Discharge Cut-Off Voltage) / 1000 = 8.96kW? I assume that I'd use the Discharge cut-off voltage as the max voltage... and this leaves it with only 9kW peak output, which is less than the 10kW of the SolarMD?

The maximum battery kW output under discharge will change with voltage (and voltage drops as the battery depletes or is put under load), so your calculation (using the lowest usable voltage) is a safe bet for the worst-case scenario (ie, low SOC).

In practice that lower voltage will only apply as SOC gets low, so the rest of the time you'll probably be close to 10kW at nominal voltage (51.2*200 = 10.24kW). And some of the time you'll have PV to bolster you (so the battery won't take the full load)

But avoid red-lining your system/batteries if you can since you don't want to trip: on my 10kW system I target an absolute maximum load of 8.5kW and have never tripped. Yet, that is.. 😃

 

2 hours ago, JayMardern said:

The maximum battery kW output under discharge will change with voltage (and voltage drops as the battery depletes or is put under load), so your calculation (using the lowest usable voltage) is a safe bet for the worst-case scenario (ie, low SOC).

In practice that lower voltage will only apply as SOC gets low, so the rest of the time you'll probably be close to 10kW at nominal voltage (51.2*200 = 10.24kW). And some of the time you'll have PV to bolster you (so the battery won't take the full load)

But avoid red-lining your system/batteries if you can since you don't want to trip: on my 10kW system I target an absolute maximum load of 8.5kW and have never tripped. Yet, that is.. 😃

 

Ok, so they probably have a similar output to the SolarMD batteries then. Roughly the same specs for a lower price. Thank you, I did not think about voltage drops as the batteries discharge.

Install finally completed. I could not be happier. Today will be the first full day of solar production (install completed late yesterday). Ended up with the 12kW Sunsynk Single Phase and Volta Stage 4 (I definitely need a second one, but this is a good start), with 28 x 560W Jinko panels.

Also very very happy with the installer and his team. So professional, and giving the industry a good name. Now I get to register for SSEG and go down that rabbit hole.

Thank you to everyone here for all the tips and suggestions. Everything went a lot smoother than I initially expected in part because I knew what I was heading into, and that's in part thanks to the contributors here.

31 minutes ago, display_Name said:

Install finally completed. I could not be happier. Today will be the first full day of solar production (install completed late yesterday). Ended up with the 12kW Sunsynk Single Phase and Volta Stage 4 (I definitely need a second one, but this is a good start), with 28 x 560W Jinko panels.

Also very very happy with the installer and his team. So professional, and giving the industry a good name. Now I get to register for SSEG and go down that rabbit hole.

Thank you to everyone here for all the tips and suggestions. Everything went a lot smoother than I initially expected in part because I knew what I was heading into, and that's in part thanks to the contributors here.

Thanks for the information. Glad you are such a happy chappy with your system and even more so with the installer. Just try and use the system and see what load you can move to PV before jumping in too quick with more battery power. Try settings for your load profile as one can never provide all the information to the installed specially with the moves to PV. 

12 minutes ago, Scorp007 said:

Thanks for the information. Glad you are such a happy chappy with your system and even more so with the installer. Just try and use the system and see what load you can move to PV before jumping in too quick with more battery power. Try settings for your load profile as one can never provide all the information to the installed specially with the moves to PV. 

Thanks. Yeah I'm already adjusting consumption to times when I just have a ridiculous amount of additional PV power (setting appropriate timers on equipment etc). The only reason I'd need a second battery is for overnight heat pumps, heating etc outside of the fireplace. But... I'm going to see what it looks like over the next week first... I only started with 80% SOC yesterday because of the late switch on... and this was Day 0.

23 hours ago, display_Name said:

Thanks. Yeah I'm already adjusting consumption to times when I just have a ridiculous amount of additional PV power (setting appropriate timers on equipment etc). The only reason I'd need a second battery is for overnight heat pumps, heating etc outside of the fireplace. But... I'm going to see what it looks like over the next week first... I only started with 80% SOC yesterday because of the late switch on... and this was Day 0.

Not sure about your heat pump/s but my ITS creates more hot water running once for 1h than running 2 times for 30min during the night. I run mine 04h-05h20 and then during the sun period. This for a 150L geyser. 

If no timers set/installed try this instead of keeping the geysers via heat pump at say 55/60°. This can save some battery power after sunset. See how you can get the geysers say only down to 45 in the morning awaiting PV to reheat after 10h if it suits when you need the hot water. 

6 hours ago, Scorp007 said:

Not sure about your heat pump/s but my ITS creates more hot water running once for 1h than running 2 times for 30min during the night. I run mine 04h-05h20 and then during the sun period. This for a 150L geyser. 

If no timers set/installed try this instead of keeping the geysers via heat pump at say 55/60°. This can save some battery power after sunset. See how you can get the geysers say only down to 45 in the morning awaiting PV to reheat after 10h if it suits when you need the hot water. 

Oh no, I was talking about my air source heat pump (aircon) for heating the lounge area. I really want to get a heat pump for my water. I think that needs to be one of my next moves. What I'm seeing at the moment is that the geyser cools down after the kids evening routine, then in the morning it's really not that warm, so I've currently got it on for about 1.5hrs at around 4am to bring it back up to temp (have a timer). I probably need to switch to a heat pump for the geyser as they are a ton more efficient... but I've realised that I also just need another battery as I'm generating a ton of power at the moment (14.2kWh battery full by 11am).

Today's graph:

Red spikes over night are from an oil heater in one of the kid's rooms (I probably need to change that to something more efficient). Then you can see the geyser spike at around 4am. At the moment Eskom kicks in when the battery drains (yellow). Then see how little PV I can actually capture from the day (that red bit from about 10:45 is the geyser another appliance on a timer).

Busy with the SSEG application at the moment. Will at least be able to push 3.45kW back to the grid through the day... but I can see a second 14.2 kWh battery in my future so that I can run a decent heat pump during the night and store more of what I capture (I could definitely use it as it stands).

Update.

My SSEG is finally active. Loving it! Yellow bar below the line is the export to COCT. This is today until 14:30 so far. I should cap out above 30kWh exported by end of day.

The sad part is that once my battery is charged... I'm missing out on so my generation still. Really wish I understood the reason to limit export to the grid to 25% of the breaker capacity. I could be pushing way more to the grid.