Hi, I have an Axpert Max II 8kW with 5.6kW of PV and 4xUP5000 Pylontech batteries. That keeps up going for most days but every now and then the sun don't shine and I need to connect the generator. I have just a 3.2kW generator because that was the most affordable inverter generator that I could find. It works fine in most cases, however I have to be very careful with total load when the generator is connected.

There are settings for maximum utility charging current but is there a way that I can convince the Axpert to limit the maximum current drawn from the generator, regardless of whether it is used to supply load or to charge the batteries?

For example, the house draws ~500W during the day, I derate the inverter 25% so I am happy drawing 0.75*3200W=2400W which is 50A into a 48V battery. So I set maximum utility charging current (setting 11) to 40A to give myself a bit of headroom. All works great until somebody turns on a kettle, at whcih time the generator is asked to deliver 40A*48V=1920W to charge the batteries plus 500W for the house plus 1.2kW for the kettle equals 3.6kW, so the generator trips.

It would be convenient if the Axpert were to limit the maximum utility current rather than the maximum utility charging current, and reduce the charging current accordingly when the load goes up. Any ideas how I can achieve this?

Thanks 

Edited April 8, 20242 yr by SteveD

7 hours ago, SteveD said:

so the generator trips.

No its not possible, and even if it was possible for the inverter to limit grid input power, then it will just mean that the inverter will trip instead of the generator! 

There is only one solution for you. You need to introduce an automation  subsystem  that is able to disable non essential load circuits via smart breakers  in the case where grid is not available.  And also the automation must limit grid charging to say 10A  during that time. 

 

Edited April 9, 20242 yr by BritishRacingGreen

Hmm, I am not sure I agree that the inverter would trip, none of its outputs are anywhere near to a limit.

35 minutes ago, SteveD said:

Hmm, I am not sure I agree that the inverter would trip, none of its outputs are anywhere near to a limit.

You might want to revisit your statement. 

When the  sum total  of all energy producers {grid, pv, battery) is less than the consumer (load) , then the inverter folds back its supplies in the form of electronically switching the producers off (current limiting example). That constitutes a trip in the same sense you lose load via a circuit breaker. 

EDIT : I have seen a nasty failure mode on Axperts where the inverter does not fold back but instead lowers the output voltage to cope with lower source  power.  Thats when I supply pv in batteryless mode with no grid. At one stage the output lowered to 120VAC which caused my pool pump to overheat.

 

Edited April 9, 20242 yr by BritishRacingGreen

I remain confused, it has plenty of energy to supply the load. The issue is that the Axpert charges at the value in setting 11, maximum utility charging current regardless of load, until the battery is full. I want it to back off utility charging current if the load increases, so in my case:

Kettle off: Generator provides 2.4kW, load is 500W (house) + 1.9kW (battery changing)

Kettle on: Generator provides 2.4kW, load is 500W (house) + 1.2kW (kettle) so it should reduce the battery charging to 0.7kW

Edited April 9, 20242 yr by SteveD

4 hours ago, SteveD said:

I remain confused, it has plenty of energy to supply the load. The issue is that the Axpert charges at the value in setting 11, maximum utility charging current regardless of load, until the battery is full. I want it to back off utility charging current if the load increases, so in my case:

Kettle off: Generator provides 2.4kW, load is 500W (house) + 1.9kW (battery changing)

Kettle on: Generator provides 2.4kW, load is 500W (house) + 1.2kW (kettle) so it should reduce the battery charging to 0.7kW

I say you cannot set the generator value. It sees it as grid and from grid it can at any time charge what your setting 11 is. The inverter doesn't know you are using a WEAK grid. 

You will have to manage the grid charge to say 15A for in case the kettle is on. 

My own view and I could be wrong. 

I don't believe that your model can do what you want (reduce charging power to achieve a power limit at the AC-in port). It's possible that the Duplex models (with two AC input ports) might do this; I'm not familiar with these.

You could maybe do it with clever monitoring software: it notices the overload, sends a command to the inverter to cut back or stop utility charging), but it may not be fast enough. By the time that the overload is detected, a decision made, the command is sent, and the charge current is reduced, the generator may have been overloaded for several seconds, and may well have tripped by then.

The inverter could probably limit the overload to a fraction of a second (say 50 milliseconds), which may be fast enough. 

[  Edit: Duo → Duplex ]

Edited October 23, 20241 yr by Coulomb

32 minutes ago, Coulomb said:

I don't believe that your model can do what you want (reduce charging power to achieve a power limit at the AC-in port). It's possible that the Duo models (with two AC input ports) might do this; I'm not familiar with these.

You could maybe do it with clever monitoring software: it notices the overload, sends a command to the inverter to cut back or stop utility charging), but it may not be fast enough. By the time that the overload is detected, a decision made, the command is sent, and the charge current is reduced, the generator may have been overloaded for several seconds, and may well have tripped by then.

The inverter could probably limit the overload to a fraction of a second (say 50 milliseconds), which may be fast enough. 

Did I then read the question wrong. 

The OP would still needs the power at AC in to stay at 2.4kW but only get the charging circuit to reduce charge as there is now a load using the power from the generator. (AC in) 

16 hours ago, SteveD said:

Axpert to limit the maximum current drawn from the generator, regardless of whether it is used to supply load or to charge the batteries?

OP asked wether the total grid  current can be throttled, it cannot. You can set the max grid  charging current but thats it.  If there is a shortfall from the dc sources, the balance  comes from the grid, up to the 5kw specification. 

Edited April 9, 20242 yr by BritishRacingGreen