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Max pv watts for Axpert inverter

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I have an Axpert 3kv/2400w inverter with max pv 600 watts input (not the "plus" model)

Currently have 2 x 250w renesola panels connected in parallel to stay within the 600w pv input inverter limitation.

Question is if the inverter max pv input watts limitation is based on the pv panel stc specs (250w, 37.4v voc, 8.31a mpc) or notc specs (185w, 35v voc, 6.57a mpc) watts. Hoping based on notc specs which could potentially mean i could still add an additional pv panel in parallel keeping me within axpert max open circuit voltage of 75v and 600w limitation.

Appreciate any advice on how to maximise pv usage based on axpert model limitation.

Thanks

*edited

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I have the KS

3Kva Axpert KS = 6 x 260W in parallel (8.42 x 6 = 50,52A) @ 30,9V specs are 50A, 30-32V

4/5Kva Axpert KS = 2 banks of 6 x 260W in parallel (8.42 x 6 = 50,52A) @ (2 x 30,9 = 61,8V) specs are 50A, 56-72V

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Edited last post after checking manual.

The 600W refers to a single panel otherwise the voltage and current would exceed the charge controller specs.

e.g. The pv panel max power for the 1Kva is 85W, but 10 can be connected in parallel without exceeding the specs. 

 

My calculations for 3Kva MKS model:

3 banks of 2 in series - 2 x 30,9V (61,8V) @ 3 x 8,42A (25,26A)

MPPT specs are 30-66V and typically 25A

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Thanks Eugene, however still concerned about max pv input watts inverter can handle with mine being limited to 600w while the plus is limited to 1500w.

Therefore hoping if this is based on pv panel notc specs (lower), i could possibly add another pv panel.

I dont believe i can run 6 pv panels on my inverter model as this = 1500w beyond my 600w limitation.

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I'm learning to swim, had another look at the specs of the 3Kva MKS.

I see Max solar charging current is 20A.

2 in parallel - 30.9 x (2 x 8.42) = 520W

2 in series - (2 x 30.9) x 8.42 = 520W

Both are within specs, seems odd to me that the KS model can handle 1500W.

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Thanks Eugene. I am already running 2 x 250w pv panels as mentioned and all calcs are based on pv panel stc specs.

Question is does one do these calcs based on stc or notc specs because if notc i could still add another panel in parallel and still be within 600w limitation of my axpert.

If calcs based on stc specs then only 250w x 2 panels = 500w below 600w limitation.

If calcs based on notc specs then possibly 185w x 3 panels = 555w still below 600w limitation.

Hoping someone can help answer this stc vs notc question.

Thanks

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Whilst I was doing research into my inverter specs I came across several posts where it seemed that people were exceeding the 3kW maximum of panels on the 5kVA Axpert. For instance on a cloudy day a 3kW array might only produce 2.5 kW and so under the same conditions a 4kW array would produce 3.3kW. The Inverter would then be powered to its maximum even under cloudy conditions. It would seem that the inverter can only utilise up it maximum in terms of Watts but the array can exceed this so long as one does not exceed the max Volts or Amps.

 

Perhaps message the fundis like Mike, Wetkit or SuperDIY and find out. I decided that 3kW was enough for me so did not pursue the matter any further.

 

Chris.

 

P.S. One needs to take VOC and temperature compensation into account to compare to your inverter max voltage and you need to use short circuit current (Isc) to work out your maximum Amps for your array. This gives you the margin of safety needed and you then know you can never exceed your inverter's specs.

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Thanks Chris,

So despite the axpert 600w limitation, i could possibly get away with two parallel strings of 500w each, total 1000w (2 x 250w pv panels) which would give me overall:

Voc = 74.8v (1

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I wouldn't be surprised if one can uprate to at least 900W, unless the panels are tracking the sun. If fixed, the optimum angle will only be attained once or twice a year.

My roof is 45deg, which is optimum for Spring and Autumn.

The MPPT must have built in protection against overvoltage and overcurrent, see Warning Codes 13 and 14.

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I'll be more than happy if i can through above, get closer to 600w consistently.

At the moment with 2 x 250w panels, the best i have seen is 390w charging at 12a for max 1hr duration.

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Agree Chris, will at some point in the future need to cut my losses on the 3k and go for the 5k (i wish i had known more about this initially).

Correct the 2 panels are 24v. Will this be problematic with the 5k and will they need replacing with 48v rather.

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I just installed a second 300 Watt Amerisolar panel. The existing one managed to pull 7.9 Amps at peak power, so assuming i should now get about 16 (Will check next weekend)

 

Using a PWM controller but want to upgrade to the Axpert MKS 3K model. I think that 900 Watts of panles will be sufficient for my needs as an end goal, but not sure if worth then going for the plus model or just sticking with the normal model and maybe being able to add a smaller panel of same voltage in parallel to ensure i dont exceed max amps. Maybe even putting a breaker between it and the parallel circuit for those cloudier rainier days?

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Whilst I was doing research into my inverter specs I came across several posts where it seemed that people were exceeding the 3kW maximum of panels on the 5kVA Axpert. For instance on a cloudy day a 3kW array might only produce 2.5 kW and so under the same conditions a 4kW array would produce 3.3kW. The Inverter would then be powered to its maximum even under cloudy conditions. It would seem that the inverter can only utilise up it maximum in terms of Watts but the array can exceed this so long as one does not exceed the max Volts or Amps.

 

Perhaps message the fundis like Mike, Wetkit or SuperDIY and find out. I decided that 3kW was enough for me so did not pursue the matter any further.

 

Chris.

 

P.S. One needs to take VOC and temperature compensation into account to compare to your inverter max voltage and you need to use short circuit current (Isc) to work out your maximum Amps for your array. This gives you the margin of safety needed and you then know you can never exceed your inverter's specs.

 

Chris, you are spot-on. The most important thing here is to never exceed the inverter PV input voltage. If the inverter specs says that it accepts 600W from PV, that simply means that the inverter can utilize up to 600W from PV, even if you have 3000W worth of panels connected, the inverter will only use up to 600W of the available 3000W. Current and power is not an issue - just do not exceed the max PV input voltage.

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Chris, you are spot-on. The most important thing here is to never exceed the inverter PV input voltage. If the inverter specs says that it accepts 600W from PV, that simply means that the inverter can utilize up to 600W from PV, even if you have 3000W worth of panels connected, the inverter will only use up to 600W of the available 3000W. Current and power is not an issue - just do not exceed the max PV input voltage.

 

But wouldnt you exceed the max amps of the inverter which may cause an error?

 

Thanks SuperDIY.

Sethm, would suggest you go for the 5kv/4000w model rather than 3kv/2400 which i found is not scaleable. Or at least get the 3kv plus model.

My max power usage on my existing inverter is about 300 Watts with Fridge running, 2 laptops and TV.

 

My average electricity bill over 3 years is R320 per month (I dont use alot of power).

 

I am able to bring in a total of 52 amps per the one panel, which would increase once i switch to MPPT which can run the fridge and a laptop during the day while i am away which fully charges the batteries as well, so just not sure if i would need more panels for where i am now.

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But wouldnt you exceed the max amps of the inverter which may cause an error?

 

Which "max amps" are you referring to. Any device, including the inverter will only draw as much current as required - current is drawn, not pushed.

 

A simple example: although your car's battery can supply the starter motor with 80A when the car is started, the parking lights will only draw 1 amp from the battery. The battery always has much more than 80A available, but the load only draws what it requires.

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Which "max amps" are you referring to. Any device, including the inverter will only draw as much current as required - current is drawn, not pushed.

 

A simple example: although your car's battery can supply the starter motor with 80A when the car is started, the parking lights will only draw 1 amp from the battery. The battery always has much more than 80A available, but the load only draws what it requires.

So even if I had 10 panels (80 Amps theoretically)  on a 25 Amp controller in parallel, this would not be an issue. Only if in series of which the voltage exceeds the controller voltage?

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So even if I had 10 panels (80 Amps theoretically)  on a 25 Amp controller in parallel, this would not be an issue. Only if in series of which the voltage exceeds the controller voltage?

 

Yes, the charge controller will only draw enough power to charge the batteries at 25A - that is in any case not 25A drawn on the PV side, but rather 25A flowing into the battery bank and limited to 25A max by the charge controller..

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Yes, the charge controller will only draw enough power to charge the batteries at 25A - that is in any case not 25A drawn on the PV side, but rather 25A flowing into the battery bank and limited to 25A max by the charge controller..

Thanks :) Then the normal 3kva should be sufficient for my needs and not the Plus model.

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So i got my Inverter today :)

This is my plan for wiring it up.

 

AC Input to come from nearby plug point.

DC Input to come from Solar panels - DC Circuit breaker (25A) to be installed during the week.

AC Output to run to Multiplug and then to required locations.

Batteries in to Inverter with DC Circuit breaker (66A) to be installed during the weak.

Does everything seem okay?

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