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Newbie 5kVA Inverter problem


bmk
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Hi All,

I am new to the forum and to the installation of domestic off grid power systems.

I have just completed the installation, in my home, of a 5kVA inverter with a 48VDC/200Ah battery bank. No solar has been installed as yet but it is planned for the near future. The inverter is branded 'MPP Solar', CPU version 00072.40,  and looks to be identical to the Axpert and Mecer models. 

My distribution board has been rewired into two sections, one side for geysers, oven and AC's, the other for essential circuits such as lighting, fridge freezers and the likes. At the moment without solar it is running in bypass mode and is working well with the exception of excessive current consumption! 

In bypass mode the inverter is drawing an additional 2A more than the output. Even with the inverter AC output and batteries disconnected the inverter is still drawing 2A. Has anyone else come across this problem. The programmable settings are as the attached WatchPower screen grab;

Regards,

Brian.

Inverter Installation.JPG

WatchPower Screen grab.jpg

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Welcome BMK. Very nice setup!

I love the batts behind perspex(?).

How do you handle the ventilation, even though you have AGM batteries?

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22 hours ago, The Terrible Triplett said:

Welcome BMK. Very nice setup!

I love the batts behind perspex(?).

How do you handle the ventilation, even though you have AGM batteries?

Hi, Thanks for the comment, it took a while to get everything together. The perspex is only on the front and one side, the bottom, back and the side next to the fridge are open.

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20 hours ago, viper_za said:

Hi bmk

It sounds like the AC charger is keeping the batts on float.

Hi, Is 2A at 230VAC not too high for a float charge? I will disconnect the battery bank and install a DC ammeter to check what the charge current is.

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2 amps is the float current.

Here you can see at 1) the float stays around 2 amps even as the inverters pull power from the bank because of a cloud.

2) when on grid power it will also stay at float of 2 amps

 

float.JPG.bc5188fb4cbd988579d456d8d5128d

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On 3/5/2016 at 0:33 PM, bmk said:

In bypass mode the inverter is drawing an additional 2A more than the output. Even with the inverter AC output and batteries disconnected the inverter is still drawing 2A. Has anyone else come across this problem. The programmable settings are as the attached WatchPower screen grab;

My guess is that it is a reactive current draw of 2 Amps. 

To verify this you would need a power meter or scope that measures both the current and voltage wave forms.

If their is a phase displacement between these wave forms caused by Capacitors (voltage lags the current) or Inductors (current lags voltage) then this will result in reactive power flow.

As you only get billed for the real power that you draw from your supply authority its not going to impact your utility bill. 

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Someone on this forum, it might have been jdp, borrowed a proper power meter and tested it. I think that confirmed that it is indeed a current draw with a bad power factor. In reality these inverters sit closer to 50 watts or so when in bypass. If I remember correctly. Which is not bad... but... you know... the blue inverter needs about half that :-P

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1 hour ago, plonkster said:

Someone on this forum, it might have been jdp, borrowed a proper power meter and tested it. I think that confirmed that it is indeed a current draw with a bad power factor. In reality these inverters sit closer to 50 watts or so when in bypass. If I remember correctly. Which is not bad... but... you know... the blue inverter needs about half that :-P

Kurt on the AEVA site reports a quiescent draw of 46W say 50W . So we looking for another 400W to account for the 2A AC draw. Float could be anything between  2-8A DC (100 -400W)  depending on how long the batteries have been in float. So a difference of 2A would not immediately be cause for concern if it was my system. If the batteries have been on float over night maybe.

 

Which is not bad... but... you know... the blue inverter needs about half that :-P Ja but you could squeeze only half of the watts out of the blue inverter (is it blue because it is holding its breath?), and how many watts does the separate SCC consume?

Edited by Chris Hobson
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1 hour ago, plonkster said:

Someone on this forum, it might have been jdp, borrowed a proper power meter and tested it. I think that confirmed that it is indeed a current draw with a bad power factor. In reality these inverters sit closer to 50 watts or so when in bypass. If I remember correctly. Which is not bad... but... you know... the blue inverter needs about half that :-P

Mine only draws 26w from the batts on bypass mode :D

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BTW how are you checking the power draw? I hope not with a efergy. If so throw it away. It is not acurate at all  i still say we should make the "How much does the inverter draw" question a sticky at the top. 99.9 % of the time new people ask that question. 

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3 hours ago, Chris Hobson said:

and how many watts does the separate SCC consume?

About 50 milliamps. At 24 V for me. So around 2 watts... :-)

I cannot remember the exact numbers, but apparently around 20W is best of class. If the Axpert manages that... I told you these Chinese boykies are learning! :-P

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21 minutes ago, plonkster said:

About 50 milliamps. At 24 V for me. So around 2 watts... :-)

I cannot remember the exact numbers, but apparently around 20W is best of class. If the Axpert manages that... I told you these Chinese boykies are learning! :-P

23w now, might be the fans

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Hi All, I checked all the readings again this morning with the inverter in bypass mode and are as follows;

Power to Inverter 239VAC/2.8A

Power from inverter 239VAC/1.38A

Battery bank (on float charge) 54VDC/150mA

Will start looking at the Local Authority meter and the units consumed.

18 hours ago, jdp said:

BTW how are you checking the power draw? I hope not with a efergy. If so throw it away. It is not acurate at all  i still say we should make the "How much does the inverter draw" question a sticky at the top. 99.9 % of the time new people ask that question. 

I have an energy unit installed but have always regarded any readings from it with a large pinch of salt.

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  • 10 months later...

This is the exact same issue that i have as well. I've recently installed the Axpert 5kva inverter and using it as a UPS until i get my solar panels installed. My concern is that a 2A current draw on the float charge is pretty significant. My previous Devel inverter had a much lower draw when on float charge. 

I've got a Smart meter installed and the kw draw is what i expect yet my Efergy meter is showing an additional 440W being drawn. It is quite strange, i don't believe that i'm being billed for it but i'd like to know where and why this is happening? Is there a setting that needs updating? or perhaps the firmware(72.40 currently) update?

Any assistance would be appreciated. 

IMG_20170123_091748.jpg

IMG_20170124_070019_2.jpg

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The Efergy meter read apparent power, it does not take the power factor into account and is therefor inaccurate on non-resistive loads. A resistive load is something like a geyser element, oven, kettle etc. Non-resistive (inductive and capacitive) loads are things making use of switch-mode power supplies like computers, mains LED lights, flat-screen TVs, DSTV, etc.etc., anything with an AC motor e.g. fridges, freezers, vacuum cleaners etc. etc. as well as other things like flourescent lights. When the Axpert inverter floats the batteries, the power factor is very bad and therefor the Efergy will read a very high consumption, luckily you pay only for real power, as measured by the traditional KWh meters and smart meters, not for apparent power.

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As @superdiy said the efergy monitor measures V x A and that gives you VA Here is a nice article on the subject   and if you are on the grid it gets a little trickier as the voltages varies between as low as 200 v to 260v and if you setup for 220v it will also have a influence on the readings you get.

Interestingly I had a quick look at my current load and with some transformers running you can see the power factor very well here

 2017-01-25_084424.png as jou can see  the power factor is currently 0.7 

In my case I also got a Efergy monitor running , just for fun , and the va rating on it is almost the same as the watts from the inverter 

2017-01-25_084519.png

Now there will be a delay between the two as it is run from different servers but still very interesting. I will check tonight how the online values compare with the live monitor in the house..

9 hours ago, PurePower said:

concern is that a 2A current draw on the float charge is pretty significant.

Where do you get that value? I am going to guess that it the charge voltage and then 2 x 48 v gives you about 100w to charge the batteries, As I am off grid I can not compare it to my system but it seems right to me , still expensive to have batteries as back up. Maybe get yourself one or two panels just to charge the batts for now and as money allows expand.

Also , and this is my opinion , do not run the house on the batts while you do not have panels. You are not saving any money in fact its costing you money.The losses is in the region of 30% so for every 1kwh you take from the batts  you will need to putback 1.30kwh to charge them..

Regards 

Paul

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