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Minus Grid Watts


kobus joubert

Question

The battery did not carry us through the night. System went over to GRID.

So this morning when the sun was doing what it was suppose to do I noticed the following:

Battery was charging 

Load was low

BUT !!! Grid Watts showed MINUS something... see the graph.

I monitored it for about 45 minutes and then decided to MANUALLY switch it to Battery (Solar) on the ICC

Immediately it switched over and the Grid Watts came to Zero.

Why would it get stuck in Minus Grid Watts.  Did I push 220 Volts back to Eskom ?  I thought these Axpert Inverters cannot do it.

But then I found out my inverter is a CLONE.  Sre they different ?

krag terug Woe 6 feb 2019.jpg

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13 hours ago, kobus joubert said:

BUT !!! Grid Watts showed MINUS something... see the graph.

Why would it get stuck in Minus Grid Watts.  Did I push 220 Volts back to Eskom ?  I thought these Axpert Inverters cannot do it.

Grid (AC input) power is inferred, not measured. The inferring involves some estimations, particularly losses of the inverter (I forget the details now). 

It won't be pushing power into Eskom, so don't worry about that. I thought if its calculated power ended up negative, it would report zero. 

13 hours ago, kobus joubert said:

But then I found out my inverter is a CLONE.  Are they different ?

This is the big unknown. From the few photos I've seen, they seem to attempt to copy the circuit and even the PCB layout quite closely, but they may have screwed up, either to cut costs, or through not understanding how the machine actually works in detail. 

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On 2019/02/07 at 7:49 AM, Coulomb said:

Grid (AC input) power is inferred, not measured.

When I wrote that, I assumed that the estimation happened in the inverter's firmware. But in fact, the inverter doesn't report its AC input power at all, so this inferring must be happening in ICC.

I think that your clone may be acting differently to what ICC expects. Typically, AC input power would be calculated as AC output power (which is measured and reported), plus estimated charging power, if the inverter appears to be charging from utility. The inverter reports total charging output current (DC amps) and PV output charging current (DC amps), so AC charging output current can be inferred as (total_current - PV_current). Maybe the total current is reporting as zero, or too low, allowing a negative result. You could cycle through the measurements on your LC Display with the buttons, and perhaps figure out what is going wrong.

I wonder if they patched the patched firmware 🤔, or the hardware doesn't work quite the same.

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