Hi Guys,

 

Just installed my:

Axpert King VMIII 5KW inverter

4x 390W JA Solar Panels

2x Pylon 2000B li-ion batteries

with the Axpert Pylon cable between the inverter and batteries to monitor the batteries through the BMS.

 

I am a few days in (Joburg weather not helping much) and really enjoying learning how the system functions.

One odd thing I noticed last night. Inverter is on SBU mode with solar only for charging.. Voltage back to utility is 48V, back to battery is 50V

Batteries were too low to run on (under 50V), so inverter was running on bypass (I confirmed this by checking the inverter itself and seeing bypass active).

However, the battery "capacity" ie SOC kept dropping regardless. Yet, batteries were not being used (checked the battery discharge graph).

See attached.

Is this normal or does this indicate something could be wrong with either of the batteries, inverter or BMS?

2 possibilities, I've read that the king has a standby usage of 200watts which might be enough to explain the drop in capacity.

 

The other depends on whether your inverter has communication with the battery or not?

1) that is extremely high, but either way, surely in line mode it should not use the battery for any "standby" power consumption? 

 

2) it shows an error if not communicating with the battery. I get that error if I disconnect the cable from the inverter BMS port. As soon as I reconnect it, the error disappears. So this indicates the cable is connected correctly and communication is happening correctly. 

The curve shows that you lost about 10% charge in 6 hours.  That equates to about 66W draw - not too far out of line with what one might expect (My Kings use 42W from the battery when in bypass mode)

One further observation: certainly on the King the battery usage when in line or in bypass mode has changed significantly with different versions of the firmware. That makes comparisons difficult unless you also know the firmware versions.

OK, I actually found a post with someone using ICC that confirms the battery drain (mine is averaging around 60w per hour) 

Is this just to be expected from the axpert range of inverters? Why is it not self powering from utility (or at least have the option of where to self power). 

Do the Goodwe and Growatt models also self discharge batteries at such a high rate? 

21 hours ago, alkit said:

Is this just to be expected from the axpert range of inverters? 

For the King model, yes.

21 hours ago, alkit said:

Why is it not self powering from utility (or at least have the option of where to self power). 

The Axpert King was built by Voltronic, the company that makes them, to serve in situations where you want 0 transfer time.  So in other words, there isn't any dip in power when you switch from "utility/solar/battery".  They way they do this is by running the inverter permanently from the DC bus.  Meaning they convert input power to high voltage DC, whether that input comes from AC, solar or battery.  Then once that is high voltage DC it is converted to AC.

This arrangement is called double conversion in the UPS world.  For sensitive electronics this is the most desired configuration because no matter what your input power looks like, your output power is always from the inverter itself.  Your input power can have any frequency, voltage or wave form and it doesn't change how the output looks.  For example when you don't run in bypass you'll notice your voltage is ALWAYS a 230v AC sine wave @ 50hz or whatever you configured the output as.

The problem is, in hardware they have the inverter permanently wired to the battery.  It can't even start up without the battery.  The reason it works this way is, if they didn't they would need to switch a massive DC load using a relay which would be incredible unreliable.

If you want something that only switches on the inverter when you need it, the non King model is better suited.

Bypass mode btw. just switches a relay that takes your input power cables and puts it out to output.  But the inverter itself is still being powered by the battery.

I think a lot of people bought the King model not realizing its target market is really sensitive electronics.  The VMIII, etc. much more ideally suited to a house IMO

Edited February 1, 20215 yr by Gnome

Thanks

Fully understand regarding the king inverter.

But my post and the post I quoted relates to the VMIII model, yet even that one is pulling from batteries to keep it running, even in bypass mode (which is a real bypass, not via DC) 

23 minutes ago, alkit said:

Fully understand regarding the king inverter.

But my post and the post I quoted relates to the VMIII model, yet even that one is pulling from batteries to keep it running, even in bypass mode (which is a real bypass, not via DC) 

My old Axpert 5kVA models also always draw self-consumption from the batteries - even when in utility mode

On my old models, the draw is somewhere around 40-45W