axpert woes?

[Gabriël]

good morning gents, 

the settings & equipment:
for my equipment specs please see signature.
attached are the program settings of the axpert.

the problem:
my axpert switches to grid under certain circumstances when there is still abundant energy at hand in the pylons and from the pvs.
notwithstanding program 12 being set at 48v, the axpert switches to grid/utility at 49.5v, i can not set program 12 lower than 48v without compromising the warranty on the batteries.
when the pvs produce sufficient to carry a load of 500w and the sun is shining, giving a capacity of at least 2kw and the pylons are 100%soc all goes well. theoretically i should be able to increase the load to at least 3kw WITHOUT having to resort to grid. BUT if i increase the load to 2.3kw with say a kettle, the axpert reverts to grid.

so the question is 'how now brown cow' :-) ?
God bless
g

axpert settings 19 9 2018.pdf

[Chris Hobson]

14 minutes ago, gabriel said:

good morning gents, 

so the question is 'how now brown cow' :-) ?

Hi Gabriel

It is good to revisit your settings. Now that you have 2 Pylontechs you could set Program 2 to 50A.

Program 26 to 53.2V and Program 27 to 53.V.

What is happening when you put on a large load is your batteries experience what is called voltage sag. It is but like unloading a lorry and all that is being handed to you is your wife's groceries (normal load) and all of a sudden you get given a 50kg bag of mielie meal - you "swik" a bit. Same with the batteries the voltage drops beyond what you would expect at the current SOC. As soon as the load is remove the voltage recovers.

The good news is ICC is approved for use by Pylontech. So if you get your cable from Riaan you can then use SOC from the Pylontech's to do your switching.

 

 

 

 

[Jaco De Jongh]

36 minutes ago, gabriel said:

notwithstanding program 12 being set at 48v, the axpert switches to grid/utility at 49.5v,

Did you ever had a BMV in the system, if its still there, can you use it to confirm the real voltage when it switches? 

36 minutes ago, gabriel said:

theoretically i should be able to increase the load to at least 3kw WITHOUT having to resort to grid. BUT if i increase the load to 2.3kw with say a kettle, the axpert reverts to grid.

I was under the impression that if the load exceeds PV the axpert switches back to Grid. It cant mix in from battery and have to switch to grid. If grid is not available, i guess it will switch over to Battery, but from what I know this is how the system operates.. @Chris Hobson?

[Gabriël]

20 minutes ago, Chris Hobson said:

The good news

and good it is indeed, also the other tips, thanks @Chris Hobson - riaan and i are working on the cable. whilst we're on the topic of good news, it is raining in vredenburg 

20 minutes ago, Jaco de Jongh said:

Did you ever had a BMV in the system

i do have one and with the help of @Chris Hobson i'm on to it 

[Guest]

@gabriel are you going off-grid?

[Chris Hobson]

44 minutes ago, Jaco de Jongh said:

Did you ever had a BMV in the system, if its still there, can you use it to confirm the real voltage when it switches? 

I was under the impression that if the load exceeds PV the axpert switches back to Grid. I cant mix in from battery and have to switch to grid. If grid is not available, i guess it will switch over to Battery, but from what I know this is how the system operates.. @Chris Hobson?

Gabriel and I discussed including his BMV yesterday. He is in the process of getting it back into the system.

Axpert will stay on solar/batteries until one of the conditions changes

1. It gets a command in Program  1 to switch to utility (ICC use this to change from solar to grid).
2. Voltage drops to below the setting 12 (back to grid). This is where we are having trouble with Gabriel's system. His setting  for back to grid is 48V as set out in the Pylontech SOP. It switched back to grid at 49.5V. What I cannot fathom is whether Gabriel's Axpert is not calibrated properly or the is some phantom load that has a spike that momentarily drops the voltage to below 48V and switches to grid. You will remember Gabriel had a post a couple of days ago with a saw tooth pattern of overnight charge and discharge. The unit will remain on grid until battery voltage exceeds the back to battery mode setting (Program 13).
3. The Axpert's 4kW limit is exceeded and the unit switches into bypass mode.

So the unit can exceed what is available from PV.

I use to have 2 Pylontechs and one has to be a bit careful in that if you try and get the 2.4kW continuous discharge from the batteries you are going to experience a voltage sag. When I was on 2 Pylontechs we could comfortably go overnight  on them but there was not enough juice in them in the morning to even run a toaster. My mother -in-law would regularly trip my system. She would say "Its 9:30 and I used the toaster yesterday and nothing happened. Why have I tripped the power today?" I would have to point out that yesterday the sun shone brightly and the batteries had recovered enough from their overnight draw down and today was cloudy and the batteries had no had a chance to recover. It just takes a bit of common sense something my mother-in-law does not have in abundance. 

With 4 Pylons I can run the microwave off the batteries with minimum voltage sag. The voltage sag is inversely proportional to the Ah rating of your battery bank.

[Guest]

5 minutes ago, Chris Hobson said:

The voltage sag is inversely proportional to the Ah rating of your battery bank.

Being off-grid is not for sissies I tell you! Respect Chris.

But it does save a whole lot of fees payable to "Chingkom". 

Still, only the brave go off-grid.

[Chris Hobson]

3 hours ago, The Terrible Triplett said:

Being off-grid is not for sissies I tell you! Respect Chris.

It is a matter of necessity. I could still be running a diesel generator (next month's fuel price hike would kill me) or at the time I could spend R 180k for about 8 km single phase earth return powerline and then have the privilege of being over charged for Eskom's electricity via the municipality. No Thanks. My total install is now about R150 k. So not for the brave just economics.

[Gabriël]

21 minutes ago, The Terrible Triplett said:

are you going off-grid?

nope... i know where you might be going with the axpert etc, or not?

 

7 minutes ago, The Terrible Triplett said:

Still, only the brave go off-grid.

the brave not wanting to toe the party line etc... 

[Jaco De Jongh]

15 minutes ago, Chris Hobson said:

What I cannot fathom is whether Gabriel's Axpert is not calibrated properly

This was  my reason for asking if there is something (BMV) in line to confirm the real voltage when it switches. 

[Jaco De Jongh]

25 minutes ago, Chris Hobson said:

Axpert will stay on solar/batteries until one of the conditions changes

1. It gets a command in Program  1 to switch to utility (ICC use this to change from solar to grid).
2. Voltage drops to below the setting 12 (back to grid). This is where we are having trouble with Gabriel's system. His setting  for back to grid is 48V as set out in the Pylontech SOP. It switched back to grid at 49.5V. What I cannot fathom is whether Gabriel's Axpert is not calibrated properly or the is some phantom load that has a spike that momentarily drops the voltage to below 48V and switches to grid. You will remember Gabriel had a post a couple of days ago with a saw tooth pattern of overnight charge and discharge. The unit will remain on grid until battery voltage exceeds the back to battery mode setting (Program 13).
3. The Axpert's 4kW limit is exceeded and the unit switches into bypass mode.

Chris I am still confused. Grid is connected, Running off PV. PV available = 2000Watt, load of 2500watt drawn.

What happens next? It cant mix, right? So it goes over to batterys, then battery voltage goes below setting 12 and switches back to grid. 

Is this correct?

[Gabriël]

23 minutes ago, Chris Hobson said:

With 4 Pylons I can run the microwave off the batteries

waiting for my ship to come into saldanha harbour..., but as usual the welcome rain uncovered roofing defects which have to be budgeted for...

[Gabriël]

7 minutes ago, Jaco de Jongh said:

I am still confused

lets assume the axpert's calibration re setting 12 is not correct, would that result in the situation i described re the 2.3kw load switching? surely not.

the 'swig' theory might hold sway BUT then my question would be, for how long should that last... surely not for the 3-4 minutes the kettle needs to boil? what sayest thou?

[Guest]

52 minutes ago, gabriel said:

... i know where you might be going ...

Stop faffing and get a real inverter. 

[Chris Hobson]

1 hour ago, Jaco de Jongh said:

Chris I am still confused. Grid is connected, Running off PV. PV available = 2000Watt, load of 2500watt drawn.

What happens next? It cant mix, right? So it goes over to batterys, then battery voltage goes below setting 12 and switches back to grid. 

Is this correct?

It helps to understand that the Axpert has basically to modes AC or PV+batteries and the two are mutually exclusive. So in the scenario above the Axpert will power the load with 2000W PV and the balance from the batteries. It can do this until the battery voltage drops to the voltage specified in Program 12 then it switches to grid.

[Jaco De Jongh]

8 minutes ago, Chris Hobson said:

So in the scenario above the Axpert will power the load with 2000W PV and the balance from the batteries.

That is where I missed it.. I was under the impression Axperts could not mix any source at all. Thanks Chris. 

[DDD]

3 hours ago, Jaco de Jongh said:

This was  my reason for asking if there is something (BMV) in line to confirm the real voltage when it switches. 

What is BMV Brand Arm en Verlore?

[Jaco De Jongh]

10 minutes ago, Erastus said:

What is BMV

Victron BMV 702 or 712. Its a Battery Monitor. A must have for wet battery's as example.

Allows you to monitor the true state of and manage  the health of your battery's. 

[DDD]

5 minutes ago, Jaco de Jongh said:

Victron BMV 702 or 712. Its a Battery Monitor. A must have for wet battery's as example.

Tnx is dit per sell of bank?

[Chris Hobson]

4 minutes ago, Erastus said:

Tnx is dit per sell of bank?

Works for the bank but does give you mid-point voltage which in lead acid batteries is important.

[Guest]

1 hour ago, Erastus said:

What is BMV Brand Arm en Verlore?

Here you go: https://www.victronenergy.com/battery-monitors/bmv-712-smart
or
https://www.victronenergy.com/battery-monitors/bmv-700

[DDD]

If one can't monitor a cell or a battery what is the use of such tool?
These tools can't tell you much if you can't monitor the 1.XV cell.

 

[DDD]

Gabriel,

Another dumb question of me. Do you have a current graph and PVvolts graph for a normal day of charge for the batteries when you have a clear day?

[Jaws]

They are not designed to save a battery they are utilized so save all your other battteries.

In other words they tell you that you have a bad apple in your basket so that you can remove it before it spoils all the other apples as well.

 

 

[DDD]

I understand but a superimposed IxV curve does all of that for you.

Edited September 19, 2018 by Erastus