AndrewM314

Hi, I'm just wondering if any of you experts know whether it is possible to increase the battery charging voltage on an Axpert MKS ii, currently the maximum charging voltage is 64V, but I would like to increase it to 67V, is this possible. Thanks Andrew

Thinking about it, Kalahari Meerkat may have the solution going through an isolation transformer, I could probably step down from 240v to 110v which would give me around 156vdc not referenced to anything, which would surely be the same as the output of the panels

thanks for the reply, that's actually how I'm using it at the moment, but I wanted to stop importing from the grid to the batteries and only use excess solar that would have been exported. Due to the cost of importing and the lead acid batteries only being 70/80% efficient. Capturing excess energy pre generation meter I would lose 20/30% of the feed in tariff due to the efficiency of the batteries.

Due to the excessive KWH price, I want to reduce importing from the grid and exporting from my solar system to the grid. I have 4kw PV array going through a grid tied Sunny Boy inverter which feeds through a generation meter generating the feed in tariff. So I want to use a solar Immersion heater booster to dump any excess solar power into some lead acid batteries rather than export it. Then I can use battery power overnight to reduce importing. I was thinking of putting a bridge rectifier and a large capacitor on the output of solar Immersion heater booster and feeding into the PV input of the Axpert.

Hi, Does anyone know if it's possible to input rectified AC into the PV input on the Axpert MKS ii. So the rectified AC would probably be around 300VDC smoothed, the issue I'm concerned about is that pv- would be essentially be connected to neutral. Thanks Andrew

I managed to repair this unit by changing the two faulty IGBT's, it's now working ok and I have just connected via WiFi, the unit ID is 5535553..., Which I think I've read before is another pointer to a fake unit, is that correct.

After reading the above post everything appears ok except that it doesn't have the little date label. Also I've Just noticed it doesn't actually have Axpert in the model name. Does this sound like it could be a fake inverter.

Thanks Coulomb for the explanation and diagram, looking at this diagram and the hfpw diagram it looks like one side of D20 goes to ground through the windings of TX7 and the other side of the diode goes to ground through the windings of TX9 so it makes D20 look like it's short circuit but in actual fact I was measuring the very low resistance of the windings. So hopefully everything should be ok, just waiting for replacement IGBT'S to give it a try. Out of interest with my diode being numbered D20 instead of D40 could that my inverter could be a clone?

I've attached a picture of D20's location

Looking at the IGBT circuit again the emitter short is ok, it connects to the negative side of the DC which is correct . The only other anomaly is D20 is short circuit, I removed the diode to test it and the diode is ok, anyone know what D20 does?

I've checked all the components around the high side gate driver all seems ok except there is a short circuit between QC1 emitter and QD2 emitter with all the IGBT'S removed, that doesn't seem right?

In the service manual it shows the par board to the left of the mppt board. Is that board usually known by another name

Quick question can the main board be tested without the mppt board and par board connected?

They are actually the IGBT's QA1 & QC1, so do you think I could use any IGBT as long as they are better than 75A/650V and would I have to change all 4 if I'm using different devices or wouldn't that matter

Thanks very much for your help Coulomb much appreciated. I'm trying to find a replacement for the faulty components the number on the device is ost75n65hm but I can't seem to find one anywhere, anyone know where I can get these or an alternative, thanks

They don't even acknowledge a short circuit at the inverter battery input terminals is a fault, so I'm having a go at repairing them myself, I've got 2 inverters 1 has a short at the battery input and the other has a 09 fault, so I'm working on the 09 fault first, I've downloaded a service manual and managed to remove the main board after a bit of a tussle, I've found 2 MOSFETs are short circuit QA1 & QC1. Is it recommended to replace all 9 MOSFETs, are there likely to be any other components that fail if these MOSFETs go short.

excellent advice from all, wish I had found this site before I first switched the inverters on. I am now trying to get some replacements from the supplier, does anyone know how good the axpert tech engineers are, I have sent them a video showing that one of the inverters has a direct short on the battery input but they still are asking me to switch the battery mcb on to the that inverter which I think is very dangerous, any comments please. Thanks Andrew

Many thanks for the responses, As suggested I'm going to add circuit breakers to each AC output. I can't seem to find an official start up sequence in my manuals, all it refers to in my parallel manual is that the AC input breakers should be switched on simultaneously which doesn't apply in my case as I have no AC input. Does anyone know the official power on sequence from totally switched off.

Thanks Steve, I'll bear that in mind in the final installation

Thanks Coulomb for the reply, that is excellent information much appreciated, I'll have a good read through the post, thanks again

Thanks for the reply, at the time of failure they where temporarily wired to an open mcb essentially the 2 AC outputs where just connected together

Thanks for the reply piper, you don't happen to know how the AC output synchronises when the inverters are in parallel

Is having no AC input a problem, the inverters should give AC output from batteries and solar only is that correct?

Hi Steve, I've disconnected the wiring at the moment so unfortunately can't send pictures, the inverters were going to be totally off grid so no AC input available

I was just thinking about the AC output side of the inverter, there must be some synchronization of the AC cycle, does anyone know how it works, is the synchronization performed through the parallel board, could it be the synchronization that has failed?