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Help me to understand my Multiplus II System


Kilowatt

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Hi Guys,

 

Hi Guys,

Please can someone explain to me the reason why i am drawing so much current from the grid when my PV being generated is close to my requirement in the picture below? Is this because the inverter can only supply 2400w continuously? (Multiplus ii 48/3000)

image.thumb.png.97a01b686082462fb541debd7827f823.png

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1 hour ago, Kilowatt said:

... why i am drawing so much current from the grid when my PV being generated is close to my requirement ...

I had similar yesterday when the dryer was running.

image.png.c8567afbecd31654066296afe7916f0e.png

In questioning that myself, having never seen it, it came to light that it is due to inefficiencies in the inverter / type of loads being powered.
Inverters are typically between 88% en 92% efficient. If the fans come on, it could become a wee bit more efficient. 

So I'm ignoring that difference as the power is "free" from the panels. 

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Right. The 88%-92% is just my own experience with this particular kind of inverter. At 88%, it means a good 12% of your power is being lost into heat and other things, which equates to a good 300W in that scenario. Also, some values on that screen are calculated from others, and the values themselves are updated once a second, so you should never expect it all to add up perfectly.

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Ok, so my inverter is working hard in this scenario and the fan is running, so it’s just not 100% efficient. No problem I can live with that. 

If I add extra PV panels, let’s say another 1000w after losses etc. how would that change the example above? Would I be right to presume, I am now generating 3500w, 3000w is going to running the load including losses and inefficiency’s, would the 500w balance go into charging the battery?

The reason, I’m asking or wanting to understand is because I want to add extra PV panels, so that I can have at least 3000w at peak to handle the bigger loads and also supplement early morning PV generation. But if the extra PV power is not going to be usable then obviously I don’t want to waste my money doing that. 

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36 minutes ago, Kilowatt said:

Would I be right to presume, I am now generating 3500w, 3000w is going to running the load including losses and inefficiency’s, would the 500w balance go into charging the battery?

Yes, I agree with you, if you have a 3.5kw array.

It is what I recently did up from 2.1kw and I see a huge difference and that is smack in the middle of Cape Town winter, with a 3.5kw array.

The improvement is so much that I am doubling my battery capacity - cheaply - just to "feel" how much I can really get out of the 3.5 kw array, in winter.

For as you, 2.4kw is dedicated to the inverter, the 1.1kw spare for earlier and later and the less than ideal sunny days. Next level is to charge the batteries during optimal hours.

If you go above 3.5kw array, and there is a case for it i.e. your MPPT can handle it AND you have a ton of batteries to charge, the cautiously do it. 

This was a good day on a 3.5kw array and no battery charging - I focus on 8-5:

image.png.e36c4d7d1546fec1611c8c820b93f720.png

 

17 minutes ago, Mstott said:

... your inverter will only make use of 2400w... 

Because currently I keep batteries fully charged, that 2753w in the above post, all of that was inverter. Seen that a few times now, above 2.4kw. and as I hear the fans speed up, I see it drops down to around 2.4kw. But yea, it is a bonus if above 2.4kw, don't rely on it, stick to the 2.4kw.

Must just mention, I have seen a peak one day of 3022w from the MPPT - none to the batteries. 🙂 

Me, I am seriously impressed. Gamble on pushing up to 3.5kw array is paying off in heaps and bounds.

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5 hours ago, Mstott said:

PV yield drop

I see the same with my VE.Bus BMS. With this battery setup there is still a float voltage, it drops the charge voltage to a lower one after a while. At that point, the solar chargers all switch off for a minute or two until the battery voltage goes down.

I don't know how the SolarMD batteries do this, but that picture looks exactly like mine does. It drops to almost zero, and then settles around the value of my loads.

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I definitely think there will be an advantage for me to add extra watts to my system. Maybe bring the total PV to about 3800w. (Probably have 3000w or just over of actual power as the panels are not 100% efficient)I will have excess power during peak, but it will also mean I should have sufficient power to power my loads in the early morning from sunrise to around 10ish and again in the later afternoons as well. Will also help boost battery charging. My extra PV will have to be on its own MPPT on east side of my house to full utilize the morning sun. The other panels have full sun from 9:30 - sunset. 

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