The right inverter for battery storage and some other Qs

[ducabi]

The concern is that from your diagram, there is no way to ever isolate the maintained supply CU from the grid. When the EPS isolator switch is on then the inverter powers the grid, via the red arrows I've added to your diagram:

I have no idea how both CUs are connected and why, but will try to trace it when i have a bit more time.
But ignoring the main CU. If i switch of the main switch in mini CU will it not remove the red arrow from mini CU to grid?

[Oldgreybeard]

The concern is that from your diagram, there is no way to ever isolate the maintained supply CU from the grid. When the EPS isolator switch is on then the inverter powers the grid, via the red arrows I've added to your diagram:

I have no idea how both CUs are connected and why, but will try to trace it when i have a bit more time.
But ignoring the main CU. If i switch of the main switch in mini CU will it not remove the red arrow from mini CU to grid?

If both CU main switches are off, then you're right, it will isolate the grid. The concern is that this arrangement is far from being foolproof, it requires switches to be operated in a specific sequence to ensure that the grid isn't accidentally back-powered by the inverter EPS output.

This is why Sofar insist that a contactor or changeover switch be used to do the switching. The specific contactor or switch type is break before make, so the grid connection is always broken before the EPS connection is made, ensuring that there cannot ever be a bit of switching finger trouble that may kill some unfortunate person working to repair a broken supply cable in the street.

[ducabi]

I fully understand everyone's concerns and agree it's a bad way to do it but just wanted to make sure my understanding of how it works is correct.

So in order to add contractor switch Ideally i should:
- feed inverter from RCBO in mini CU (not from main CU)
- investigate and remove whatever connection is between both CUs
- add contractor switch to mini CU.

Then earth rod.

[Oldgreybeard]

You can follow the diagram in the Sofar manual for your inverter (I believe you have the HYD3600) and fit a manual break before make switch, as shown on this page from the manual (not sure why your electrician didn't just follow the manual, TBH):

Sofar HYD3600 manual EPS switching.jpg (83.04 KiB) Viewed 1331 times

This is safe, as the switch has to go through the "0" position when switching from grid power for the backup CU to inverter EPS power - there is no possibility of the inverter back feeding the grid.

This is the type of three position isolator/changeover switch specified by Sofar for the HYD3600: https://www.cef.co.uk/catalogue/product ... witch-ip65

[ducabi]

This is the type of three position isolator/changeover switch specified by Sofar for the HYD3600: https://www.cef.co.uk/catalogue/product ... witch-ip65

Would it look like this in my case?

[Oldgreybeard]

This is the type of three position isolator/changeover switch specified by Sofar for the HYD3600: https://www.cef.co.uk/catalogue/product ... witch-ip65

Would it look like this in my case?

Yes, that's right. The three position switch can either be set so that power to the smaller CU always comes from the EPS connection on the inverter, always comes from the grid, or can be isolated. The changeover switch ensures that there is no way that the EPS output from the inverter can ever accidentally back feed to the grid, so is inherently safe.

[dangermouse]

Sofar do have firmware to allow 90% DOD. They won't release one for 95%. They also now do firmware for the US5000 batteries as well. Its all available on line if you search.

Can anyone point me to the updated firmware for the HYD3600-ES? My inverter reports it has software version 3.40, and won't allow the battery to go below 15% (ie 85% discharge).

I can't find anything for this model on sofarsolar.com. Thanks!

Edit - furthermore, the inverter just put the batteries to standby mode at 24% charge. But reading back it was suggested that the batteries take a few days to "settle in" - this is a brand new installation and the batteries are on their first cycle. Inverter gave an "ID085 battery low" error. I rebooted the batteries (ie turned them off and on again) and they are now discharging again. So I'm not worrying for now

[Tinbum]

Can anyone point me to the updated firmware for the HYD3600-ES? My inverter reports it has software version 3.40, and won't allow the battery to go below 15% (ie 85% discharge).

https://drive.google.com/drive/folders/ ... k8Co7mVNuk

but yours is already later.

[dangermouse]

Can anyone point me to the updated firmware for the HYD3600-ES? My inverter reports it has software version 3.40, and won't allow the battery to go below 15% (ie 85% discharge).

https://drive.google.com/drive/folders/ ... k8Co7mVNuk

but yours is already later.

Thanks. That's odd, I don't have the option to discharge below 15%.

And without a backup of what I've currently got, I'm reluctant to install different software to try it out.

I get the impression this Sofar software might be a bit buggy! My batteries reached 15% today, so the inverter stopped discharging as you would expect, but then decided to start charging the batteries at 500W for some reason. I switched to passive mode and then back to "time of use" mode and that stopped it.

I just know I'm going to have to get up in the middle of the night to check the batteries start charging during the cheap rate time!

[nowty]

I get the impression this Sofar software might be a bit buggy! My batteries reached 15% today, so the inverter stopped discharging as you would expect, but then decided to start charging the batteries at 500W for some reason.

One of the settings is Voltage Protection, there is a high and a low one, although if your using it via BMS you wont be able to change it.

If the batteries goes high the inverter will force discharge and if the batteries go low the inverter force charges irrespective of the time of day/night.

That may explain the unexpected charging, although it shouldn't if the settings are all correct and you have no other DC chargers or DC loads connected.