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The Axpert will do this if you go to Grid during the day.  It transfers load to Grid... doesn't need PV therefore the MPPT drops off to almost zero load from panels... then I use my DC Disconnect on t

Hi Jaco My system is simple. I have a 200l Kwikot geyser which I have modified to accommodate two 1500W universal elements. In most situations only one port would do. In my system one is powered

Looks more impressive also

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HI Noobie 

1 hour ago, Noobie said:

After about 15 minutes I went to go and check the load the house was pulling and found that the inverter was showing no solar input, like the panels had been disconnected! 

Is this on the LCD? No PV input like it shows at night? Are you powering DC geyser element using PV?

 

This is troubling. I have had not a moment's trouble from my 4kW unit. In fact it has become a glorified whiteboard.

 

Chris

 

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1 hour ago, Chris Hobson said:

HI Noobie 

Is this on the LCD? No PV input like it shows at night? Are you powering DC geyser element using PV?

 

This is troubling. I have had not a moment's trouble from my 4kW unit. In fact it has become a glorified whiteboard.

 

Chris

 

Hi Chris, the display shows no PV symbol just as if it were night.

I haven't yet connected the geyser to solar. After all the hassles this inverter has given me I am reluctant to fiddle with it anymore

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1 hour ago, The Terrible Triplett said:

Sjoe Noobie, I sincerely hope you find the problem, that it is something small.

Maybe a fellow Axpert users in your area that can maybe pop in? A 2nd set of eyes can sometimes help.

Good plan, anyone in JHB want to come and cast an eye on my install to see where I may have gone wrong?

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My guess, something popped in the MPPT. It worked fine at low power levels and stopped working when called upon to do real work. Don't know the topology used in that MPPT, synchronous or async, but my guess would be something in the switching chain broke and the main MOSFET that drives the buck converter is not turning on anymore. So the result is no current. The display side of things interprets that as night time.

Short term solution might be to use an external charge controller, if you have one.

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I dropped of my inverter at Mustek this morning, lets see what they find.

@flltech I Im afraid I dont have monitoring software so I can't offer up this info. I though it could also be an issue with site but as far as I can tell the install is ok, MCB's earthing, cable size etc?

I have 2 strings of 3 series connected vitrus ii 250w panels, with a max VOC of 112,2v DC at NOTC, this is well within the 145v DC max input.

I have never had the circuit breakers connected to the PV panels trip so I can't imagine its got anything to do with the panels?

When testing the PV input terminal on the inverter yesterday I had both PV circuit breakers on and I was measuring 98v DC at the inverters PV input terminal, I turned off the PV breakers then tested the voltage on each breaker separately and found them both to be 98v DC.

What I found odd was that when I turned off the PV circuit breakers the input terminal didn't drop to 0 volts immediately, it dropped slowly over a couple of minutes to 0 volts.

Just to be sure this had nothing to do with the panels, I disconnected the PV input cable and tested for voltage. I got 98vDC when the MCB's were on and when turned the MCB's off it dropped to 0 volts instantly. I again measured the PV input terminal voltage with no cable connected to it and it was still dropping voltage slowly?

The strange thing about this all is that the 220v side and the battery charger and inverter are all working 100%, its only the solar side of things that has died.

 

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1 hour ago, Noobie said:

What I found odd was that when I turned off the PV circuit breakers the input terminal didn't drop to 0 volts immediately, it dropped slowly over a couple of minutes to 0 volts.

The voltage dropping slowly is an indication of the presence of capacitors on the MPPT input side, which is standard. If the MPPT was working (supplying some form of load) the V would have dropped fast, but if it dropped slowly it is just an indication that it is either open circuit (burnt track on the pc board or blown fuse or popped component etc. etc.) after the cap(s) or no current was drawn further on in the MPPT.

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3 hours ago, Noobie said:

it dropped slowly over a couple of minutes to 0 volts

Minutes? Well, those caps are usually fairly huge... but they usually self-discharge in an hour or so. The volt meter itself is also a load, so a slow drop over several minutes means that thing is completely open circuit. Blown fuse, circuit board or MOSFET. Ie I concur with @superdiy.

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I'm actually trying to find a schematic now. Thing is, you don't really need capacitors on the input side of a buck converter. You do need large caps on the output though (to keep the voltage ripple in check).

https://en.wikipedia.org/wiki/Buck_converter

Nothing bad will happen if you put capacitors on the input side, you usually put them there to reduce input ripple... except PV panels have no input ripple, so often MPPTs won't have caps on the input side (those would be fairly expensive caps too, with a Voc of 145V).

If there are no caps on the input, but you are seeing the steadily dropping voltage on the input... that might mean the output capacitors are in circuit, ie there is a shorted mosfet rather than a blown one.

Anyone have the schematic? Can't figure it out from the Service manual.

Edit: From the service manual the smaller model has a bunch of Schottky diodes in the MPPT unit, so it's probably a asynchronous design (Diode passively conducts the back EMF rather than a MOSFET actively doing it).

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So Mustek emailed me saying that my inverter was ready for collection.

I called the technician to find out what had caused the failure and he said that the bus which runs between the PV input at the board was not making decent contact.

I can only imagine that it wasn't fastened down correctly when they installed the new MPPT.

This would make sense as when the unit was only pulling a small amount of power to keep the batteries on float there was no issue, however when the power draw increased due to load shedding the contact burnt out.

I hope to collect it this week and connect it up this weekend

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I have been thinking (probably a bad sign) that the caps on an Axpert does not leave much headroom and the failures  seen maybe attributable to this. TTT is going to do flick-flacks.  I have AGM batteries and the bulk charging voltage is 56.4 volts and it drops down to 54.4V for float. The Axpert's inability to maintain voltage under circumstances like a fluctuating heavy load (ironing) or when the sun comes out behind a cloud has been discussed before and Dockarl's experience in Aus springs to mind. It is normally about 2-3 seconds but it does go over your bulk voltage. My BMV has a log of over voltages  and the highest experienced is 58.6V a whole 2.2V higher than the setting for bulk. Now if bulk is set to 59.2V  for a battery like the Trojan then 2.2V on top of that then I think we are entering TTT white smoke territory. 

So my recommendation is that if you have an Axpert use batteries that do not have a high bulk voltage requirement.

  I can see TTT firing up the Bellvile XR6 to come and donder the Engelsman.:P

 

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17 minutes ago, Chris Hobson said:

I can see TTT firing up the Bellvile XR6 to come and donder the Engelsman.

You meant Isuzu ... nope, not going to donner anyone. Patience. Watching. Listening. Reading. :D

But yes, your thoughts are spot on - but dang, to not have Trojan T105RE's, now THAT is sad. :P

 

FWIW, that little 350VA Edmund fixed for me, with the new controller I horse traded after you so astutely pointed out to me 12v and 2 x 200w panels are not maaitjies (faceplam for missing that on my side) with 4 x 105ah free batts are powering 75w 24/7. Switched it on and forgot about it.

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So the newly repaired Axpert has been installed and has been running on SOL for a week now with no issues. 

This week council decided to supply only 170volts to our home for most of the day, the inverter disconnected the council supply and we ran off of batteries and solar for most of the day with no issues.

Now that I know the MPPT is working correctly I am going to set the Axpert up as UTI so that just acts as a UPS when there is a power failure, hopefully this will help to make it last a good couple of years because the MPPT won't work as often (only when there is a council power failure)

Now I am stuck with 1,5kw worth of PV panels sitting on my roof doing nothing during the day..... Any ideas?

I though about doing a Geyserwise MPPT to heat the geyser off of PV but now I am leaning towards getting a little grid tie inverter and just having it push the power produced by the PV into the 220v side of my home. 

Any thoughts regarding this? I will need to start filling up the piggy bank before I do anything, I was just looking for some guidance 

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5 hours ago, Noobie said:

So the newly repaired Axpert has been installed and has been running on SOL for a week now with no issues. 

This week council decided to supply only 170volts to our home for most of the day, the inverter disconnected the council supply and we ran off of batteries and solar for most of the day with no issues.

Now that I know the MPPT is working correctly I am going to set the Axpert up as UTI so that just acts as a UPS when there is a power failure, hopefully this will help to make it last a good couple of years because the MPPT won't work as often (only when there is a council power failure)

Now I am stuck with 1,5kw worth of PV panels sitting on my roof doing nothing during the day..... Any ideas?

I though about doing a Geyserwise MPPT to heat the geyser off of PV but now I am leaning towards getting a little grid tie inverter and just having it push the power produced by the PV into the 220v side of my home. 

Any thoughts regarding this? I will need to start filling up the piggy bank before I do anything, I was just looking for some guidance 

Get a 1KW element and geyserwise timer, and run your geyser between 10AM and 2PM. 

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5 hours ago, Noobie said:

leaning towards getting a little grid tie inverter

This one, but it is a cool 23k. Comes with a standard 5-year warranty and you can extend it up to 15 years (though that will likely add another 30% to the price). Why the Galvo? Because it has a boost stage and only needs 140V to start up. Perfect for people with smaller arrays.

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I've always liked the look of the Fronius inverters, have no experience with them though. Wouldn't it be better to go for a 3.1 or 5kW? See the price difference is minimal and allows for future expansion. You should be able to get a better price than 23k, that's the price on Sustainable and they're not what I would describe as competitive.

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4 hours ago, TinkerBoy said:

The Axpert is does not let your panels work all the time. That is why I looked at switching things on during the day from AICC. But then I decided to just get rid of the Axpert and get a grid tied inverter that I do not need to baby or manage. 

I'm thinking along the same line with a GTI, however with the Microcare grid tied inverter disconnects the 220v output when there is an eskom power failure, leaving the PV panels to collect dust. 

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3 hours ago, SilverNodashi said:

Get a 1KW element and geyserwise timer, and run your geyser between 10AM and 2PM. 

I was considering this but then I am restricting my options, I can only heat my geyser.

With a grid tied inverter I can power anything connected to the 220v wiring in my house, including the geyser.

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2 hours ago, plonkster said:

This one, but it is a cool 23k. Comes with a standard 5-year warranty and you can extend it up to 15 years (though that will likely add another 30% to the price). Why the Galvo? Because it has a boost stage and only needs 140V to start up. Perfect for people with smaller arrays.

If only it had a battery bank connection it would be great.

Oh yeah, and if only I had R20k lying around!

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I was going to say, sell the Axpert, then it struck me, who will a) buy it and b)) at what price to get easier to R23k ... scrap that idea.

Mense but I hate it when good people spend good money and then are stuck when unforeseen problems surface.

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