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Axpert 3Kva MKS with more than 600W solar panels


giant122
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Please advise,

 

I have a Axpert 3KVA MKS with a 24 V 100Ah battery bank and 2 x 300 Watt Renesolar 

solar panels. For the setup I am using it it works fine.

How will the inverter handle an aditional  300W solar panel as the total allowable wattage is 600w

to get the batteries to full charge faster during winter times and during cloudy days in the summer..

Will the additional watts being waisted or will it be a better configuration to use an additional solar regulator.

please advise

 

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I believe that's a PWM model. PWM chargers cannot handle oversizing. It will let the smoke out of something. 

Even for mppt, in my experience, 50% is pushing it. I've done it with a bluesolar mppt and it complained of the occasional overcurrent event. I would not do it on a voltronic. 

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Hi Giant122,

The Axpert 3kva mks Plus is little more expensive and can take up to 1500w panels because it is an MPPT version,but the mks is PWM version and  is only allowed 600w,

Why dont buy an 60A MPPT charge controller and hook it up on you battery bank and it will allow more panels.

 

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2 hours ago, giant122 said:

I have a Axpert 3KVA MKS

The 3kVA MKS is an MPPT system. You can add the additional panel capacity without causing damage as the MPPT will only draw what is can handle. You will get better results in early/late times of the day and in less than optimal conditions, but not more than the system can handle (probably a little more than 600w) during optimal PV hours.

Note that putting 3x 300w 72 module panels in series will come very close to (and possibly exceed) max system voltage on a cold clear day or when cloud edge effect comes into play - you may be ok but just giving you a heads up.

 

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I was thinking of the MKS 5k when I said 3 panels in series may exceed max open circuit voltage, in the MKS 3k it will definitely exceed MOCV.

You can go with 3 panels in parallel and you should be fine (36V and 25A), if you want more panels than that then I would recommend upgrading to the PLUS version or the MKS 5k.

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Even if it's an MPPT model, I'm still wary of oversizing by 150%.

Simply, there is some latency inherent in the control algorithm of these chargers. It uses a closed control loop, whereby it adjusts the mark/space ratio it uses to drive the Buck Converter, using feedback it gets from a current sensor. There's often some filtering involved as well, so that the control loop adjusts smoothly and doesn't oscillate. It is conceivable that during partly-cloudy days, cloud edge effect could make your charge current swing up faster than the control algorithm can adjust it down.

My personal opinion remains that oversizing should be kept between 120% and 130%.

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  • 1 month later...

I installed a lot of inverters branded with Effekta name-http://www.effekta.com.de/epages/63928138.sf/en_GB/?ObjectPath=/Shops/63928138/Products/SLAMVTSI

AX-K 2024(PWM)is working without problems with 1500W of PV panels.

AX-M 4048(MPPT) can handle 5000W PV panels. They have limitation for the input current.

I oversold the power of the panels in order to have charging even in cloudy days.

See here my works: www.ecowindsolar.ro

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  • 3 years later...
On 2018/01/03 at 6:46 PM, ___ said:

Or try it and tell us if it worked... 🙂

@___ I tried just that, though inadvertently and no surprises so far going into a year (I touch wood).

Initially I had 2x315W Yingli panels in parallel on an Axpert MKS 3K-24 (PF1) with 600W/75Vdc MPPT. I then added another 2x315 panels that were lying around. That is a whopping 1260Wp on just a 600W MPPT (oversized by 101.6%)

Using a clamp meter, I measured roughly 4.56A from each of the 4 panels at noon and recorded the following PV parameters on the Axpert display: 630W, 37V and 17.55A.

@Coulomb, could it be that the Axpert MKS 3K-24 will take a maximum of 630W irrespective of how large an array is oversized? 

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On 2021/02/26 at 11:01 AM, Kilowatt Power said:

could it be that the Axpert MKS 3K-24 will take a maximum of 630W irrespective of how large an array is oversized? 

Yes, they'll all limit the SCC power to a safe value under ideal (slowly changing) conditions. But in the real world with clouds and loads switching on and off, the PV vharge current control system, designed for 625 W (25 A @ 25 V) will overshoot and undershoot quite badly with a 100% oversizing of the PV input. It might be your battery (quite possibly more expensive than the inverter) that blows up eventually.

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