Wolfgang Griech

here a few pics of my original MK-II installation with those Noctua NF-A8 silent fans:

as you can see I have swapped the yellow and green wires of the Noctua extension cable before directly gluing them onto the PCB, after pulling the original white connector bodies from it. There was no other reasonable way without cutting the Noctua cables, which I have done now anyway for the VM-III

sorry for the double post, but my Internet here is really broken right now, so I though the first time didn't work....

On 2021/08/11 at 1:52 AM, Peter Merle said:

I have the same fans here since more than a year, but didn´t install them so far.

I´m running a MPP Solar PIP 5048GK that should be identical to the Axpert VM-III - MPP Solar provided a firmware update that reduced the fan noise under lower charge, but cannot provide a solucion when the fans are running with full speed.

@Wolfgang, did you invert the fan blowing direction?

@Peter: yes I did on the original MK-II, but found out that the inside of that inverter is really dusty and even dirty, so at the VM-III now (yes, I did this the day before yesterday) I kept the original direction, blowing out to the bottom. I know this is against all good design rules and against the natural flow of the heat, but the dirt and the fact that there are non-removable non-cleanable filters on the inside of the inverter made me think a bit, so guess for now I'll stay with the original direction. This time I also decided to cut off the original fan connectors with about 5cm, and solder them to the Noctua NF-A8 fans, after I discovered that those geniuses used one connector with 3 pins and the other one with 4 pins:

this is the soldering connection between Noctua (left) and the original fan connector (right), yellow-right is connected to RPM = green-left, PWM is not used at the VM-III, they probably just control the fan voltage:

the whole installation of the 2 Noctua NF-A8 fans looks like below, it is quite tough to pull the brown plastic holders of the Noctua due to tight space: 

and finally a pic of the non-removable non-cleanable filters, the only good idea I would have to clean them is to use a vacuum cleaner from the outside, and this only works if we maintain the original direction of the fans, else those filters will get plugged from the inside:

On 2021/08/11 at 1:52 AM, Peter Merle said:

I have the same fans here since more than a year, but didn´t install them so far.

I´m running a MPP Solar PIP 5048GK that should be identical to the Axpert VM-III - MPP Solar provided a firmware update that reduced the fan noise under lower charge, but cannot provide a solucion when the fans are running with full speed.

@Wolfgang, did you invert the fan blowing direction?

@Peter: yes I did on the original MK-II, but found out that the inside of that inverter is really dusty and even dirty, so at the VM-III now (yes, I did this the day before yesterday) I kept the original direction, blowing out to the bottom. I know this is against all good design rules and against the natural flow of the heat, but the dirt and the fact that there are non-removable non-cleanable filters on the inside of the inverter made me think a bit, so guess for now I'll stay with the original direction. This time I also decided to cut off the original fan connectors with about 5cm, and solder them to the Noctua NF-A8 fans, after I discovered that those geniuses used one connector with 3 pins and the other one with 4 pins:

this is the soldering connection between Noctua (left) and the original fan connector (right), yellow-right is connected to RPM = green-left, PWM is not used at the VM-III, they probably just control the fan voltage:

the whole installation of the 2 Noctua NF-A8 fans looks like below, it is quite tough to pull the brown plastic holders of the Noctua due to tight space: 

and finally a pic of the non-removable non-cleanable filters, the only good idea I would have to clean them is to use a vacuum cleaner from the outside, and this only works if we maintain the original direction of the fans, else those filters will get plugged from the inside:

2 hours ago, sunset1 said:

What did you pay for those fans and where did you buy them from may I ask?

sure, no secrets about any of this, am happy to share it, but I'll have to tell you I'm living in the Philippines, so no clue where you could buy them from. My source was Lazada, an Asian small version of Amazon, here's a link for buying at Lazada, and you wanna chose the 12V 4PIN PWM version of it:

https://www.lazada.com.ph/products/noctua-nf-a8-80mm-computer-cooling-fan-12v5v-3pin4pin-pwm-quiet-radiator-fan-for-pc-case-cooling-cpu-cooler-replace-fan-i1750436467-s7493248143.html?

the cost is right now quite exactly $30 USD / piece, so quite expensive, but IMHO well worth the money, in our case the inverter is outside in an open shed just a couple of meters away from our bedroom, so quite annoying at night when everything is silent and you'll sleep with the windows opened. And those fans are really silent, and also no ball bearings or alike, I think it's magnet bearings, with an MTBF of 100,000h or alike, so very likely you'll never have to exchange them again.

today I'll take them out from the old inverter and transfer them into the new Axpert VM-III 5kVA, I'll take some pics of the wiring and share it here later.

This is my solution for the noisy fans of the MKS-II, it isn't cheap, but extremely good, there is basically zero noise anymore. The only issue when upgrading to those silent fans is the screwy pinout of the fan connectors of the MKS-II, some pins have to be swapped, but no bigger deal, the NF-A8s comes with some extension cables which can be misused for that purpose, so the connectors of the fans themselves can remain as they are. Mine are perfectly running since about 3 years by now, and I'm just upgrading to an Axpert VM-III, and the same issue there, so the fans will now move to that inverter.