ryanb

Download the Axpert MKS IV user manual, the pinouts is in the BMS section. The same pinout is used for MKS III  and VM III / IV models as well. The RS485 pins are 3 and 5, cannot remember which is A and B. 

Yes that would also fix it

Hi @GreenFields,

Many thanks for taking the time to respond in such detail - it really helped to clarify my understanding.

I have a few more comments and queries in response to your post (and all these questions pertain to scenarios while grid is not present) :
For clarity, is this "solar power" setting a minimum solar generation value? So in my case would the MPPTs need to be harvesting a minimum of 4000W before it considers switching power to the AUX port?  I always thought this was a maximum value, and hence my confusion.
So if the battery SOC is at 100% AND there is more than 3000W of PV generation, I would assume that the AUX port would be active.  Then, let's assume there was some temporary shading from a cloud.  Would you expect the AUX port to switch off during the shading?
I also found the attached document which was very helpful.

Best regards,
Ryan
 
 


 
AUX LOAD Sunsynk Explanation.pdf

Hi Dom, yes it does work.  The advantage of powering the geyser on the output side of inverter, is that you can still heat your water during load shedding.

I have a 8KW Deye unit, I have a theoretical max of almost 24A on my parallel string (460W panels) and my inverter clips the current above 20A. I have seen it clip the current on nice sunny days (but I only have 4S2P). So you should be ok over-panelling on current if you do not mind the Watts that you paid for that will not be used.
Personally I would rather install 640W panels and put 8 in series for a total of 5120W per MPPT. Assuming that you have the roof space with the exact same orientation and no shading
The MPPTs can also only handle a certain amounts of watts, 10400W if I am not mistaken so anything over 5200W per MPPT will be wasted power. The MPPT can only handle a certain amounts of watts and will heat up accordingly so they normally thermally throttle them with the software or they will give an error and shut down. The MPPTs work independently of each other so you need to stick to a number around 5200W per MPPT
You are not going to get the benefit of 18 Panels on one MPPT. Rather split them over the 2x MPPTs or get smaller panels or do not put parallel panels.
 

If you've set the solar power setting to 4000W, but you've only got 8x460W panels attached (3680W max), then you'll never see the AUX activated. Nevermind the fact that you've got East and West-facing panels that are sub-optimal, but in total your panels can normally never generate 4000W.
The AUX depends on excess solar AND sufficient battery.
Try to see the logic as follows (and I'm not saying I'm 100% right, but just at least try it out):
1. The AUX functionality lies somewhere between essential load and non-essential load.
1.1 - If the grid goes down the non-essentials go down, but the essentials will still be feeding from the solar and battery systems.
1.2  The point of the AUX or Smart load is, if the grid goes down, you can still get useful power for some of your nice-to-have loads, but ONLY IF there is enough battery AND solar power available.
1.3 If you don't have enough of either solar or battery resource as per your settings, then the AUX will switch off, and only the essentials will remain, if the grid has gone down.
2. In your case I would try to set the AUX solar power setting to around 3000W (at least below your mid-day peak generation, whatever that is) and run the geyser on AUX at mid-day in the event that the grid goes down. It would have helped if you had more solar available, say 5000W peak, to give you a better chance, a longer time in the day when your solar production is well above the geyser load of 3000W. But in any case set the work mode for "zero export to CT" so that you can blend some solar power on most days if the grid is on, even if you don't get enough solar to run solely on AUX.
A bit long-winded, and partially based on Deye menu settings, but the ideas should be the same. Hope it makes sense. I'm not discussing the on/off scenario for when the grid is present, but menu option should exist also.

As far as I know, it is about the Signal tick boxes on the Battery Set-up->Battery Charge. You can either use the output signal for "Signal Island mode" or else for "Gen Signal". You can't it use both (There can be only one! - Highlander hahaha). As we know the "Signal Island mode" will kick the relay for the bond when the grid goes down. If you use the "Gen signal", it can be use to auto start your generator based on various options you can set on the System mode as well a the Battery Set-up->Battery Charge page (Gen Max Run Time and Gen Down Time). If you start the Gennie manually, you should still be able to use the signal for "Signal Island mode" - Maybe some of the Sunsynk experts out there can confirm?
 
Just a question on the Sunsynk Neutral - Earth Bond - I have a Distribution Board (DB) on the non essential load (LOAD) side. Can I just add a cable from the Neutral bar in the DB to the relay and a cable from the Earth bar in the DB to the relay? So when the grid goes down, the relay kicks in (using the "Signal Island mode") and links the 2 for the bond?

Yes, I see it there now. But it’s only mentioned as some obscure note in that older Training manual. In the newer Installer manuals there is no mention of that. I would guess, this is only valid, if you use the AUX for GEN input and not for LOAD out. Otherwise, it doesn’t make much sense to me, looking at the block diagram of how everything is connected in the beginning of the same manual - page 13. 
 
But maybe someone more experienced could clarity it for us.