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JHenry

Axpert MKS 3kva 24v plus: Mppt not taking much power from Solar Panels

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Dear All, kindly help me.

I have the following setup

1. Axpert MKS 3kva 24v plus.

Spec: 145Voc, mppt max 1500watts

2. 6 x 320watts Flames Solar panel. Spec: 8.28Imp, 38.86Vmp, 8.86Isc, 45.85Voc. 3 in series and 2 parallel strings. Total power= 1920w

3. Four Tubular 220ah batteries; two in series and parallel

My observation is that during midday when the sun is at its peak, and batteries are fully charged,( I.e batt: 0A, batt: 27.7v), the inbuilt charge controller have not taken load beyond 980watts even when it seems it should draw more power from the panels with great reserve. Please any reason for this?

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14 hours ago, JHenry said:

during midday when the sun is at its peak, and batteries are fully charged,( I.e batt: 0A, batt: 27.7v), the inbuilt charge controller have not taken load beyond 980watts even when it seems it should draw more power from the panels with great reserve. Please any reason for this?

I'd say most of it is because of your excessive Voc: 45.85 x 3 = 137.6 V. That's over 130 V, where the SCC starts ramping down maximum power (assuming that 24 V SCCs behave the same as 48 V SCCs; it could be lower than 130 V). That means it has less than full power to pull the panel voltage below 130 V, so that it can then operate at full power. The SCC might be reporting as "not OK".

You also have a lot of PV for your model, 128% of rated maximum. This makes the SCC a bit touchy (a small change in PWM results in a larger than expected change in charge current). I don't know if that would lead to lower PV use. You can probably get away with this.

So you should rewire your panels for 2S3P instead of 3S2P.

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On 2020/02/10 at 1:31 AM, Coulomb said:

Huh. I'm used to patched firmware (I'm a co-author of the patches), where discharge and charge current are combined into one display, with a minus sign if it's discharging. That still doesn't show the contribution purely from utility charging, but with low loads, but as utility charging starts ramping up you see the battery load reduce and go positive (if utility charge current is higher than that needed to supply the load).

I guess they figured the displays are cluttered enough already, and they haven't yet copied our AussieView™ innovation of cycling the left and right information displays independently. That way, we provide more information (e.g. this combined charge/discharge current, inverter temperature) with fewer button presses. Maybe they'll catch up one day. Our patch software is free, and the trademark thing ("™") is purely tongue in cheek.

Alas, there is no patched 24 V firmware.

Yea. I thought of rewiring it to lower the VOC. That is, 2S3P as I wasn't sure. I would give it a try. I also noticed that the max power it was able to pull , the PV was below 90v. Thanks 

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I have a similar setup with a 2KVA version of that unit and with Canadian solar 335W panels with a custom LiFEPO4 setup with 180Ah.

I have the panels connected in 2S3P configuration and with setting 2 set to 60A.

What setup do you have in terms of priorities of solar/utility ?

 

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