That’s another problem in itself, best case you can only store it for about a year.
I have done the math multiple times on this, with current stages of loadshedding and diesel price a gennie is definitely not worth it. (Even if you got it for free)
Interestingly a 50kVA Gennie is more expensive than a 50kW SunSync, a 60/48 HV FreedomWon I think will probably be about R400k, if I have to guess that’s probably only 3-5 years of fuel.
Not even to mention the hassle of servicing, noise and refueling.
I am not saying the gennie is bad as a backup, I just would not make it the primary backup source.
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If I have to buy more panels/batteries or a gennie, I will buy a good small gennie for WEATHER only:
- Will throttle the inverter to meet the 2kw diesel gennie,
- Switch off breakers left and right on the Critical loads DB to meet the inverter.
- To use most of what the gennie can do, to recharge the batt when the weather is a bother.
Ek is nou moeg.
I have reached the end of the line where I try and keep up to cater for worsening conditions after 15 years. More so after recent events, I’m chasing my tail here.
Differently put:
The people in this house will cut their HOBBIES to MY NEEDS level. 
(Or go and buy your own dammit!)
EDIT: And the weather is only in winter.
So yeah, chances are remote.
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In parallel each 50 kw inverter needs its own battery bank. You can not use a common DC bus, which makes management a bit complicated.
The high voltage batteries are also pretty expensive.
Thanks gents for all of your inputs. It’s great to have such a knowledgable forum dedicated to what is essentially a South African problem. I definitely didn’t mean to start an apocalypse discussion though. I’m still interested for any further feedback on the Sunsynk 50kW inverter - @ebendl please let me know how your installation goes.
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Just to be absolutely clear: it isn’t my installation. The IT company that I work for decided to put up a PV system and I was not at all involved in the decision making, tech choice etc. Since I’m an enthusiest I noticed the boxes in the basement where I park and looked into what they’re installing.
When I say I can give feedback I meant along the lines of “ok we switched over and everything is working nicely” or “wow the power tripped for the 8th time today they must be struggling” type of effect. We have a big generator and we’re quite aware at the moment when the power goes out 
Sorry!
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Thanks @ebendl for all your assistance and your DM.
They seem solid in the field, we have 2 running an engineering firm and they are running the complete place off the inverters, been running for a couple of months without major issues. A few firmware upgrades were needed to get the parallel function working near perfect. Some changes will still be done in the near future. The new 100kw will hit the market soon. Its price is lower than 6 x 8kw or 3 x 16 kw…
You would need to get an installer that did the training on the 50kw. Even us in distribution had to attend the training before we could start selling these and we are only allowed to sell them to installers with certificates.
Installation is pretty simple but extra care should be taken when connecting the batteries. I would not recommend a battery bank lower than 460V, any mistake with that voltage can cause serious damage to equipment and or injury to yourself.
EDIT: The 50kW can only work with a few approved batteries. Freedom Won HV, Blue Nova HV and if i remember correctly the SolarMD.
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Thanks Jaco, that’s good to hear. Do you have any experience regarding repair times?
Did SunSynk not recently change their policy that if your repair takes longer than 2 weeks, they will send a replacement?
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I dont want to start on that. Waited for repairs for 3 months and longer. They do have a new policy, if you can prove the inverter is in the repair centre for longer than 2 weeks, they will replace the unit with a new one.
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Hi there Jaco, great to see some serious expertise on this 50kw 3 phase SunSynk model.
Could you answer this burning question involving the runtime of these units based on the server rack of 12 or more batteries here. They are connected in SERIES and though, technically, the total wattage is + 60kw.
Would these batteries run for 3 hours if the draw demand from the inverter is 20kw? Or does this 50 kw 3 phase SunSynk inverter run at 50kw no matter what?
The reason for all this confusion arises out of experience with Low Voltage units (48v) but this High Voltage approach has truly left in me in a quandary.
Any help would be appreciated in understanding this at the end of the day in a decision to purchase.
Hi, the inverter will only supply the load drawn at any time up to a max of 50kw.
Being a high voltage battery the conversion from 460 Volt DC to 230Volt AC will be very efficient and sunsync claims 98% efficiency in this conversion. The losses will be much lower than trying to convert 51.2 volts dc to 230volt Ac. With a low voltage system you need to allow for the conversion losses as well as the 20% you want to remain in the battery. Most lithiums you dont want to discharge below 20%.
With the losses being minimal in this setup you will have more usable kwh in the battery bank, but your 60kwh bank at a constant load of 20kwh will not run for 3 hours. Roughly you will have 2.4 hours runtime up to 20%.
I would recommend a Freedom won 80/64 HV as the minimum size battery to ensure 3 hours runtime at 20kwh loads.
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Everything works the same, except the conversion efficiencies’ are higher and the dc current lower.
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On the topic of HV. If you start from 800V it becomes even better. You don’t need a full bridge to shape a 230VAC sine wave (RMS, so peak at 325V, which is why you need about 400V on each side of the line to do the work). I’m excited to see what the industry is going to do in this new direction.
What is more… electrical cars may well shoot for an 800V too in future, which will result in an impressive amount of technological overlap. V2G (vehicle to grid) is going to become a whole heap easier and more efficient, and a lot of the electronics you’d use for the one can be used almost unchanged in the other.
Exciting times!
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I think pretty much all EVs these days are 800V-1000V. But I would not peg that as an advantage. If you center-tap the pack for a Neutral, any asymmetric loads will destroy your cell balance in a way that is difficult (or pretty much impossible) to correct. In the end, I have a feeling that 400V with a full bridge will be a superior option.
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Yea, if you center tap the battery and use half a cycle from each half, and you thought DC ripple issues were bad…
But I’m pretty sure you have to be isolated from mains anyway (to be compliant, and it also gives you the means to control the current ripple if you design for it). This is where about half of the savings from losses come from. If you decrease current by going higher voltage, you move away from the square trap in I²R with your magnetics (a gapped PQ65 seems to be a popular choice). Some more savings come from the same trap with the MOSFETs. At the higher voltages, you probably want to use SiCFETs, instead of IGBTs, because with IGBTs your frequency is too low and then you need a bigger core, which means more losses (+more core losses from lower freq, a double-whammy).
To me, this makes sense why HV is only starting to become mainstream - SiCFETs are only starting to become mainstream.
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Wandering waaayyy off topic here, but I find this idea very interesting. While you don’t need to be isolated from the battery, it does make life a lot easier.
But then you are in the same boat as pretty much every HF LV inverter out there. They all have an HF isolation transformer generating 400V for a full bridge inverter. It would be trivially easy to mod these to an 800V centre tapped transformer and go with a half bridge - but no one does this.
I assume there are still some significant cost savings at lower voltages to warrant double the component count. But maybe that will change as SiC MOSFETs become more common.
There is a couple of trade-offs in doing so - your active devices on the other side of the transformer need to handle double the voltage(well depending on your design), but more importantly your window in the transformer will only allow half the copper per leg, which means you double the resistance, which squares the losses half the time, so you end up with double copper losses. This you need to tradeoff with your active device losses (can be half the number of devices).
But that is just for one direction. I have not thought about how bidirectional would work in this case.
@JacoDeJongh do you know if there are there any major differences between the Deye and Sunsynk 50kW Hybrid inverters? Apparently Sunsynk is now only sold with Freedom Won batteries and my advice is that the the Weca battery has better specs?