Inverter lying about power in Watts, but reports correctly in VA.

[luk88]

Hi, one of my two 10.2kW Y&h inverters (some Voltronic Axpert clone also known under PowMR, Sumry MPS VIII Eco and other brands) is lying about the load power. 

 

It is showing 300W load power even in a middle of a night (in battery mode) when nothing is using it. The battery current going in bounces between 0 and 1A so I know it is really only on self consumption of up to ~50W (this is at 53V battery voltage). At the same time Load VA shown much more realistic value that bounces between 18VA to 60VA.

 

I thought perhaps it is some current sensort/transformer, but wouldn't it use the same CT for measuring output current as one used for the VA calculation? 

 

My second unit is much better, but still it's load Watts seem 50W too high. 

 

Does anyone know if there is some way this can be corrected by setting some internal potentiometer or replacing resistors perhaps? 

[TaliaB]

6 hours ago, luk88 said:

Hi, one of my two 10.2kW Y&h inverters (some Voltronic Axpert clone also known under PowMR, Sumry MPS VIII Eco and other brands) is lying about the load power. 

 

It is showing 300W load power even in a middle of a night (in battery mode) when nothing is using it. The battery current going in bounces between 0 and 1A so I know it is really only on self consumption of up to ~50W (this is at 53V battery voltage). At the same time Load VA shown much more realistic value that bounces between 18VA to 60VA.

 

I thought perhaps it is some current sensort/transformer, but wouldn't it use the same CT for measuring output current as one used for the VA calculation? 

 

My second unit is much better, but still it's load Watts seem 50W too high. 

 

Does anyone know if there is some way this can be corrected by setting some internal potentiometer or replacing resistors perhaps? 

The apparent power is a combination of both reactive power and true power. True power is a result of resistive components and reactive power is a result of capacitive and inductive components. Almost all circuitry on the market will contain a combination of these components. Since reactive power takes away from true power, it must be considered in a system to ensure that the apparent power output from a system is sufficient to supply the load. This is a critical aspect of understanding AC power sources because the source must be capable of supplying the necessary volt-amp power for a given application. As with any product, understanding the needs and specifications of the end user will ensure a successful application.

A volt-ampere (VA) is a measurement of power in a direct current (DC) electrical circuit. The VA specification is also used in alternating current (AC) circuits,but in this case, it represents apparent power (represented in VA), which often differs from true power (represented in watts). In DC circuits, VA and watts (W) are equal

Edited August 24 by TaliaB

[Youda]

7 hours ago, luk88 said:

It is showing 300W load power even in a middle of a night (in battery mode) when nothing is using it. The battery current going in bounces between 0 and 1A so I know it is really only on self consumption of up to ~50W (this is at 53V battery voltage). At the same time Load VA shown much more realistic value that bounces between 18VA to 60VA.

 

First of all, try to run the inverter with it's output totally disconnected from the house circuits. Just the inverter running from the batteries. Then check if it is still reporting those 300W or not. Most of the times these strange numbers are being caused by the small electronics that's plugged into the house's circuits. Even if the devices like TV, audio, phone chargers, etc. are switched-off their power supplies are being energized and may cause reactive power draw.

Well, only if the inverter will be reporting those 300W even with it's output leads disconnected from the house, then it's a case for a repair/calibration.

[Coulomb]

I know nothing about the Powmr / Must models, except that they started as Voltronic clones but now have their own firmware.

The usual situation with Axperts is that they will report 300 VA AC input with no load, but zero watts. The 300 VA is the imaginary power consumed by the smoothing capacitor.

I suppose the inverter's reporting may be swapped or confusing.

In the Axperts, the same load voltage and current measurements are used to calculate the load actual power and apparent power, using proper Root Mean Squared instantaneous power averaged over a complete 50 or 60 Hz cycle for the real power. There are no potentiometers inside; there are digital equivalents (scaling values stored in EEPROM). It's sometimes possible to adjust those values, but Voltronic hides them all. Only the battery voltage is moderately easy to adjust. With Must / Powmr, I have no idea how to calibrate even the battery voltage.

Edited August 26 by Coulomb

[luk88]

21 hours ago, Coulomb said:

I know nothing about the Powmr / Must models, except that they started as Voltronic clones but now have their own firmware.

The usual situation with Axperts is that they will report 300 VA AC input with no load, but zero watts. The 300 VA is the imaginary power consumed by the smoothing capacitor.

I suppose the inverter's reporting may be swapped or confusing.

In the Axperts, the same load voltage and current measurements are used to calculate the load actual power and apparent power, using proper Root Mean Squared instantaneous power averaged over a complete 50 or 60 Hz cycle for the real power. There are no potentiometers inside; there are digital equivalents (scaling values stored in EEPROM). It's sometimes possible to adjust those values, but Voltronic hides them all. Only the battery voltage is moderately easy to adjust. With Must / Powmr, I have no idea how to calibrate even the battery voltage.

You are exactly right. Thank you

I record the data from my inverters via modbus (a small script I wrote that reports to MQTT, from there it goes to homeassistant and grafana). I got the register numbers here https://github.com/odya/esphome-powmr-hybrid-inverter/blob/main/docs/registers-map.md and they are indeed swapped for VA and Watts. I rarely go to where the inverters are installed in person, but the other night (when there is no load at all on that inverter as only things it powers are washing machine, dishwasher, microwave etc, appliances I know are off when everyone is asleep) and I saw it was reporting about 300VA and almost no Watts of power.

So this solves that mystery.

Now I have another one... The inverter is supposed to consume 75W idle power (not ideal, but not horrible either). I also measured DC power drawn at the same time(using a DC clamp meter set to 40A) and I saw 2.3A (at 53V). To me this seems pretty excessive. 75W is 1.4A at this voltage. It is set to appliance mode (I heard these inverters consume more in UPS mode, because it has to be always in sync with the grid.).

But also I noticed it is in almost perfect sync with the grid when in battery mode even set to appliances. So perhaps this software just pretends to switch to appliance mode? What do you think?

 

 

[Coulomb]

On 2024/08/27 at 9:31 PM, luk88 said:

The inverter is supposed to consume 75W idle power (not ideal, but not horrible either). I also measured DC power drawn at the same time(using a DC clamp meter set to 40A) and I saw 2.3A (at 53V). To me this seems pretty excessive.

DC clamp meters use Hall Effect devices, which are notorious for drift. Did you zero the reading with the clamp near but not around the cable, then make a reading  immediately after clamping? My apologies if this is all second nature to you.

On 2024/08/27 at 9:31 PM, luk88 said:

It is set to appliance mode (I heard these inverters consume more in UPS mode, because it has to be always in sync with the grid.).

But also I noticed it is in almost perfect sync with the grid when in battery mode even set to appliances.

The Axperts always sync to the AC-in if present and within specification. I would expect the Musts to behave similarly.

With Axperts, the APL versus UPS setting (AC input range) determines two things: the tolerance for AC-in voltage (APL is more tolerant), and whether the SCR board is used to speed up the AC-in to AC-out relays (only happens in UPS mode, as far as I know). Power draw in UPS and APL modes should be very similar; the SCR board  should not draw significantly different power between the two settings.

[Youda]

Exactly. At these small currents, DC clamp meters are lying all day long. And the inverters themselves are not better either (I saw a couple of inverters that were calibrated to report 0A when the draw from the battery was 1,5A).

The best is to check the current reported by the BMS. If that's possible, of course.

[Scorp007]

2 hours ago, Youda said:

Exactly. At these small currents, DC clamp meters are lying all day long. And the inverters themselves are not better either (I saw a couple of inverters that were calibrated to report 0A when the draw from the battery was 1,5A).

The best is to check the current reported by the BMS. If that's possible, of course.

This in a way is actually good. This means the self power is not seen as load power. The reported battery current is then due to the load that is on. 

The older Axpert/Mecers have a battery current on the right hand side where is displays load values. 

[Youda]

Well, I'd prefer to see the real amps as the self-consumption of the inverter is not constant, but is higher for the bigger loads.

Also, one might think that the battery is being charged by 1A, but in reality it's being discharged by 0,5A

Personally, I log the amps that I get from BMS via CAN bus, same with the SoC. Still not 100% perfect, but as close as possible, I would say.

[Scorp007]

21 minutes ago, Youda said:

Well, I'd prefer to see the real amps as the self-consumption of the inverter is not constant, but is higher for the bigger loads.

Also, one might think that the battery is being charged by 1A, but in reality it's being discharged by 0,5A

Personally, I log the amps that I get from BMS via CAN bus, same with the SoC. Still not 100% perfect, but as close as possible, I would say.

Luckily I see the readings as an indication and if I need higher accuracy I use the equipment meant to get readings. Very much like a car speedo. Few readings that can read say 200A will be accurate below 10A.

To me the function of an inverter is to produce power when needed but that's just me. More things in life to be concerned about than a SOC reading that is 2% out

Getting back to the post of the OP. A 200A maximum battery current is bouncing between 0 and 1A. This is not a train smash to me. 

Edited August 28 by Scorp007

[luk88]

I thought I replied after @Coulomb's post, but I must have forgotten to hit submit or something, because I'm not seeing my post...

 

  

On 2024/08/28 at 3:45 PM, Coulomb said:

DC clamp meters use Hall Effect devices, which are notorious for drift. Did you zero the reading with the clamp near but not around the cable, then make a reading  immediately after clamping? My apologies if this is all second nature to you.

It is second nature to me, but no need to apologise, it is a very valid point  I always hit a button marked Ref. I also  do it right next to where I'll be doing the measurement (before clamping on to the wire) to avoid the possibility of somthing nearby messing with the reading. 

On 2024/08/28 at 3:45 PM, Coulomb said:

The Axperts always sync to the AC-in if present and within specification. I would expect the Musts to behave similarly.

With Axperts, the APL versus UPS setting (AC input range) determines two things: the tolerance for AC-in voltage (APL is more tolerant), and whether the SCR board is used to speed up the AC-in to AC-out relays (only happens in UPS mode, as far as I know). Power draw in UPS and APL modes should be very similar; the SCR board  should not draw significantly different power between the two settings.

Interesting and very good to know.

 

On 2024/08/28 at 5:05 PM, Youda said:

Exactly. At these small currents, DC clamp meters are lying all day long. And the inverters themselves are not better either (I saw a couple of inverters that were calibrated to report 0A when the draw from the battery was 1,5A).

The best is to check the current reported by the BMS. If that's possible, of course.

I also don't trust my clamp meter that much, but I have 3 inverters hooked up to the same bank of batteries so I can only see combined current on the batteries (on the batteries side I have a Victron Smart Shunt to measure the total and each battery in the bank has its own BMS).

On 2024/08/28 at 7:30 PM, Youda said:

Well, I'd prefer to see the real amps as the self-consumption of the inverter is not constant, but is higher for the bigger loads.

Also, one might think that the battery is being charged by 1A, but in reality it's being discharged by 0,5A

Personally, I log the amps that I get from BMS via CAN bus, same with the SoC. Still not 100% perfect, but as close as possible, I would say.

I too would prefer self consumption to be included, perhaps the best would be a menu setting, we can wish...

On 2024/08/28 at 7:48 PM, Scorp007 said:

Luckily I see the readings as an indication and if I need higher accuracy I use the equipment meant to get readings. Very much like a car speedo. Few readings that can read say 200A will be accurate below 10A.

To me the function of an inverter is to produce power when needed but that's just me. More things in life to be concerned about than a SOC reading that is 2% out

Getting back to the post of the OP. A 200A maximum battery current is bouncing between 0 and 1A. This is not a train smash to me. 

Yes, I wonder how precise the SmartShunt really is. It is supposed to have 0.1A precision. At 500A maximum. I have to compare the data with my BMSes, but then which do I trust? It's like in this saying, a man with a watch knows the time, a man with two watches is never sure.

[luk88]

Ok, I've done more testing... Including with different meters. 

 

And I have to say the reality much worse than I expected. For example both of my 10.2kW inverters consistently report over double the current on the PV inputs when it is fairly low. For example. Today (during a very rainy day) I observed the current be around 0.5,0.8A solid. Inverters were consistently reporting 1.6A~1.8A. I never noticed any discrepancy when the current reaches the top limit of the input. 

 

Same, but even worse happens on battery input, but here one inverter was a lot better than the other (maybe because one was pulling from the battery and the other was charging?) . The one that was discharging only had about 20% error at ~6A. 

 

But the charging inverter was only pushing 1-1.5A into the battery, but it was reporting 7A!

 

This is insane. 

 

Since I deployed my system electricity was seemingly "escaping" somewhere. Now I know it has not been escaping. It was being measured very badly. 

 

Can someone please comment if this is normal with 10kW voltronic clone inverters? It is as if they are adjusted to measure high range of current at a cost of horribly inaccuracy at low range.

 

Does everyone use external sensors? If so, can someone suggest some hall sensors for the pv? (as precise as possible current up to 30A) 

 

Also kwh meters for 240V AC that take into account power factor in their measurements and are easy to get data from? (preferably via local WiFi or serial).