Pietpower

Not very inspiring if it is spelt Hoselest on the front of the battery?

On the left of the heading is a blue dot. Click on that.
Presume this is when on a computer?

I vaguely remember studies that scaling actually increased the efficiency of a heating element due to the larger surface area. 
Up to a point and not applicable to boilers etc.

It is about striking a balance.  If your solar panels can produce say 4kW and the battery can deliver say 2.5kW you have a total of 6.5kW available but can only use 5kW.  Not a problem imho, your savings might be slightly less and your battery might last a bit longer with less load or cycling on it.

Firstly distinguish between kW and kWh
Vacuum maybe 0.75kW and used for say 30min 0.75 x 0.5 = 0.375kWh
Washing machine on cold cycle?
Then what else do you use during the day? Dishwasher? Iron? Kettle?
Then you will have two scenarios in my opinion. 
- Daytime with base load (fridges, wifi etc) and high kW short time items
- Night time with base load with maybe some added stuff like lights, tv, phones charging or whatever your profile is.
(night time load also drops after bedtime)

For argument lets say you use 2.8kWh during the day for intermittent / higher load appliances and an average base load or 300W (0.3kW x 24h = 7.2kWh) to make up the 10kWh used.
Your battery is 5.12 x 90% = 4.6kWh usable
Day: 4.6-2.8=1.8/0.3= 6hours
Night 4.6/0.3= 15hours
Just for illustration on a best guess and your figures might differ depending on your load profile.

The first calculator on this page can calculate time for you
https://bloglocation.com/art/water-heating-calculator-for-time-energy-power

Firstly distinguish between kW and kWh
Vacuum maybe 0.75kW and used for say 30min 0.75 x 0.5 = 0.375kWh
Washing machine on cold cycle?
Then what else do you use during the day? Dishwasher? Iron? Kettle?
Then you will have two scenarios in my opinion. 
- Daytime with base load (fridges, wifi etc) and high kW short time items
- Night time with base load with maybe some added stuff like lights, tv, phones charging or whatever your profile is.
(night time load also drops after bedtime)

For argument lets say you use 2.8kWh during the day for intermittent / higher load appliances and an average base load or 300W (0.3kW x 24h = 7.2kWh) to make up the 10kWh used.
Your battery is 5.12 x 90% = 4.6kWh usable
Day: 4.6-2.8=1.8/0.3= 6hours
Night 4.6/0.3= 15hours
Just for illustration on a best guess and your figures might differ depending on your load profile.

I was looking for some info on my Kwikot heat pump recently, on the Kwikot site they say that if you want to reduce the amount of power that your geyser uses, and don't want to replace anything then
1) Turn the thermostat down (they say 60, we have 55 in our house and find that satisfactory and we don't have to blend in any cold)
2) Take showers rather than baths
3) Take short showers

They think timers don't make much difference in terms of consumption because when the timer does kick in the water is colder and takes more heating. They think blankets aren't necessary on new, SABS compliant geysers.
You can also try fitting water saving shower heads. There are lots of rubbishy ones around, but good ones (eg RTS) have some clever innards that generate multiple small but powerful jets of water whilst restricting flow. That doesn't directly affect the geyser, but it means you let less hot water out of it.

These are the things from which domestic sulks may arise.  I decided to give an RTS head a go a while back and the wife actually found it superior to anything we'd had before. So I bought another for the 2nd shower. They lasted us about 15 years and last year I replaced them. The new ones can be set on a really miserly setting.

They come with a special key for fitting them, because in Germany people used to nick them from the B&Bs, so they were modified so that a regular spanner is no good and vice grips will mangle them.

The fitting with the key also means that unless you have the key or are willing to leave a visibly mangled shower head as evidence you can't change it from the aforementioned miserly setting to merely restrictive.
 

I am in the same boat with no support from Goodwe.
The Sems portal also seems to have problem on it.

It need not. The reason as I understand it the 2nd life are say 120Ah that have lost 20Ah and 100Ah is the current capacity. With a linear loss of capacity over time and discharge cycles I still think a 2nd life of 100Ah can loose this capacity at the same rate as a new battery. 
I use some ex laptop batteries for camping LED lights. They might only have 300mAh left but some are 12 years old. 18650 cells. Some are used everyday and built into a torch with magnetic strip and always stored on a door steel frame.
I stand to be corrected.
PS The S-120 is R1200 cheaper on the powerforum store than the bidorbuy link you posted earlier

Geewiz have them I think 
 

Seems you are mixing options here.
Splitting:
- Do you have enough space in the DB or do you need to add another DB
- Can you do this yourself and issue COC or will you need someone for the COC
- It requires a fair amount of extra breakers and wiring and work even if you do it yourself
- The backup breakers are feeding from the inverter so always on (no switchover)
Switchover:
- Manual.  It is an either/or situation but not both grid power and backup power.
- Not sure if, or how an automatic system will work.
- You have a delay or short interruption in power.
- Don't know of anyone using such an option
Direct or everything on:
- Since everything runs through the inverter your inverter needs to be big enough for the highest load.
- For me with geyser and stove etc that would be 8kW and up. My neighbour does this with two axpert inverters
- The saving on not splitting your DB can go to a larger inverter.
PS Larger inverters normally use 48V batteries while some of the 3kW inverters can be 24V thus saving on batteries if you just want to bridge loadshedding.
Maybe an additional small DB for the backup circuits with a 3kW inverter is the cheapest option for you.
Another option is to install the Inverter close to the load or equipment to be on backup and have an outlet at the inverter using leads to all your equipment. You will then need some floor standing lights or something.

Seems you are mixing options here.
Splitting:
- Do you have enough space in the DB or do you need to add another DB
- Can you do this yourself and issue COC or will you need someone for the COC
- It requires a fair amount of extra breakers and wiring and work even if you do it yourself
- The backup breakers are feeding from the inverter so always on (no switchover)
Switchover:
- Manual.  It is an either/or situation but not both grid power and backup power.
- Not sure if, or how an automatic system will work.
- You have a delay or short interruption in power.
- Don't know of anyone using such an option
Direct or everything on:
- Since everything runs through the inverter your inverter needs to be big enough for the highest load.
- For me with geyser and stove etc that would be 8kW and up. My neighbour does this with two axpert inverters
- The saving on not splitting your DB can go to a larger inverter.
PS Larger inverters normally use 48V batteries while some of the 3kW inverters can be 24V thus saving on batteries if you just want to bridge loadshedding.
Maybe an additional small DB for the backup circuits with a 3kW inverter is the cheapest option for you.
Another option is to install the Inverter close to the load or equipment to be on backup and have an outlet at the inverter using leads to all your equipment. You will then need some floor standing lights or something.

Popular belief say so but no the energy is not much less.  With electrical it is also highly dependent on water usage.
With electrical 200L you lose heat through the day. The geyser says 1kWh per day but with piping etc I lose about 2kWh in reality.  To heat the 200L takes about 10kWh from cold. That is a loss of about 16% (2/12).  Now if I use that 200L over 4 days the loss is 8/18 or 44%.  If I have a 150L and heat it twice a day then the loss is probably below 10%.
With a gas geyser the chimney is not ice cold so some of the energy is also lost. Maybe also 10%??
So IMHO the energy used is similar and it boils down to what you pay for electricity vs gas per kWh.
Where you can really save on an electrical system is if you can put excess energy from your solar PV system into the water and then you can triple that energy with a heat pump.

Just guessing on figures here but cooking can take 1-2kW of energy per hob while a gas geyser can maybe be 14kW of energy or more.  A 48kg for a gas geyser can easily be used up in 2 months.

I have underfloor heating (and cooling in the summer) running off a heatpump (home made system in my case rather than commercial). I would recommend underfloor heating to anyone, best heating system I've ever installed).
In my case (North east Spain) I heat the water to typically 32C in winter and chill to 16C in summer, this keeps the house at around 25C in summer and 22C in winter. 
As there is a time delay on the response I use a weather feed and predictive heating based on forecast temperature, always working 2 hours ahead. I also reduce the temperature a few degrees overnight in the winter.
My house is approx 250sq meters and electricity use is between 6000kWh and 8000kWh (depends on the winter!) for a heating season from mid October to mid may.
In my case I have also added (and soon to add more) solar water panels to the system so on sunny days I get free heating from the sun. As the underfloor is effectively a thermal mass the heat is available long after the sun has gone.
Another future plan is to add an extra small heatpump that operates when I have excess solar power. This will most likely only be for summer cooling use and 'emergency' winter use in case of grid failure.

If you only have only one geyser then it is not easy to get satisfaction from vacuum tube system.  I think it may be a reason why so many are unsatisfied by solar water heating systems:

A solar system can only heat once in a 24h period while electrical or gas is available whenever you want it to be.
You may have nice hot water in the evening for showers but then find that the water is cool for the morning shower.  Now you need to find ways around this. People don't want to work around problems and then just complain about the shit system.  Same with a cloudy day having to manually go to a backup.
One way around this is to have electrical heating in the evening to top up to desired temperature and then do the same again in the morning before showering.  But now you start the day with mostly hot water in the geyser and lose most of the energy savings you could have had from the solar water system.  It needs to start with as cold as possible water in the morning to have the best efficiency.
Bottom line for a solar water system is you need a lot more water storage to have an efficient system. Best is if you have more than one geyser in series imho.

Just to add some more for comparrison.
Standing losses on our 200l geyser including pipework is 2kWh per day when no water is used.  On your heat pump that will ad another 0.5kWh with a total of 2.5kWh
We use about 150-200l of hot water a day. Instead of heating it twice a day I added another 150liters to give 350L storage.
Our inlet temperature is closer to 20C (15C in winter). That is the temp to be used in the calc if all 200L in the geyser is used but when only part volume is used and then the start temp is different.
We use a geyser setpoint of 65C. This effectively increases the hot water storage capacity since we use less hot water when showering.  At 55C you will mix more hot water with cold water to achieve the desired temperature thus use up the hot water faster.  
The 150L geyser is combined with a cost effective flat plate collector and pump and in series and in front of the 200L geyser. Thus it preheats the water and the 200L geyser uses less electrical power. The cost for the added geyser, flat plate and pump with installation was about R10k.
We average around 4kWh per day in summer with the above setup and it is also supplied from PV solar.

Could you please explain this please.  If all our breakers are SANS then why do you need SANS approval for an additional device?
Many of us have Sonoff switches in our supplies which is not SANS rated.  Is it illegal if I install that inside a DB board keeping the circuit breaker in place as opposed to installing it just outside the board?  Does it matter if it is upstream or downstream of a breaker?
What my logic tells me is that you have a certain size breaker to protect a certain size cable. If you remove that and replace it with the wrong size or unapproved (non SANS) then you will COC problems. If you install a contactor or breaker close to usage it should not be a problem.  If you install same inside the DB is it then a problem?

I have a Goodwe but now wish I had a Sunsynk 8kW
Goodwe is easy to install and works as it should but it has many negatives in my opinion.
First I struggle to get support from Goodwe. 
The settings are a bit limited. Example you can set max discharge to say 10% and grid available discharge to 30% so you have 20% left for load shedding but that is about it.  I understand the Sunsynk has more options.
The interface or nice graphs is via the internet.  So somewhere in China the data is kept and my only connection to it.  I can't connect directly to the inverter to download data.  Currently my graph values do not correspond to what I am using in reality (it jumps to say 6kW while I am actually using only 4kW) and nothing I can do about it.
 

I have a Goodwe but now wish I had a Sunsynk 8kW
Goodwe is easy to install and works as it should but it has many negatives in my opinion.
First I struggle to get support from Goodwe. 
The settings are a bit limited. Example you can set max discharge to say 10% and grid available discharge to 30% so you have 20% left for load shedding but that is about it.  I understand the Sunsynk has more options.
The interface or nice graphs is via the internet.  So somewhere in China the data is kept and my only connection to it.  I can't connect directly to the inverter to download data.  Currently my graph values do not correspond to what I am using in reality (it jumps to say 6kW while I am actually using only 4kW) and nothing I can do about it.
 

I have a Goodwe but now wish I had a Sunsynk 8kW
Goodwe is easy to install and works as it should but it has many negatives in my opinion.
First I struggle to get support from Goodwe. 
The settings are a bit limited. Example you can set max discharge to say 10% and grid available discharge to 30% so you have 20% left for load shedding but that is about it.  I understand the Sunsynk has more options.
The interface or nice graphs is via the internet.  So somewhere in China the data is kept and my only connection to it.  I can't connect directly to the inverter to download data.  Currently my graph values do not correspond to what I am using in reality (it jumps to say 6kW while I am actually using only 4kW) and nothing I can do about it.
 

Thanks again.  Will try that.
From your image and my photo the panels most likely have three strings per panel and the shadow would bypass 1-2 strings at a time losing max 2/3rd of the output per panel.  That equates to a 5% loss in output per array of panels.  A broken diose could place a restriction in the system causing a much higher loss in output.
The comment above about the panels not being designed for shading and being damaged also makes more sense now.

Is a single string all connected in series?  I presume it is in my case.  Below is an image of panels.  PV1 is the row above and PV2 the row below.
You can see the shading is very little.  Reluctant to move panels or chimney to address shading before investigating other possible causes for the following reasons.
1) Today PV2 took a dip between 12:30 and 13:00 and then shot back up when the shading from the chimney was solid on the panel.
2) Although it follows a pattern it does not happen at exactly the same times each day.
3) The output for the string dips by 50% while the shading is only on one panel.
4) Last year and the year before I never had this issue but the shading was exactly the same.
 
Someone told me that panels are not designed for shading and might be damaged.  Could this be the case?
What other reasons could there be for current drop?
- damaged panel?
- loose connections? (already checked the incoming protection panel)
 

Well. Surely at least one of your panels gives you low amperage and that pulls your entire string down. If you look at the scheme of the system, you will see a couple of interesting data, which are the daily highs of Vmp and Amp for each chain. Good luck !