Off grid inverter Panelage.


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Davo99
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Posted: 03:43am 06 Aug 2022      

Got a bunch of GTI's that are all over clocked by at least double on the panels and been running them 4-5 years no problem.

I keep reading that off grid inverters connected to batteries CANNOT have more panels amps than specified on them.

Can anyone tell me if they KNOW or have experience if this is correct or not?

Far as I can see the panels aren't going to push power, the inverter will only take what it want and leave the rest. Is this correct or something I'm missing?

I want to be able to do like I do with my GTI's and that's make sure they are making all the power that is available early and late especially and connecting them to double the panels name plate power would be the way to do that.

I am aware that the string Voltage has to be in limits but I'm talking about a parallel setup to make sure all the amps the inverter wants is available for the greatest time possible.

I am looking at either an MPP or a make sky Blue inverter charger.

Clockmanfr

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Posted: 07:27am 06 Aug 2022      

  Davo99 said  Got a bunch of GTI's that are all over clocked by at least double on the panels and been running them 4-5 years no problem.

I keep reading that off grid inverters connected to batteries CANNOT have more panels amps than specified on them.

Can anyone tell me if they KNOW or have experience if this is correct or not?




"I keep reading that off grid inverters connected to batteries CANNOT have more panels amps than specified on them."

You will need to be more specific?


In a Off Grid situation where your main off grid inverter,  ie battery voltage to 230vac and your GTI's are AC  coupling. ie, connected into the 230vac Mini Grid your main Inverter is creating. Then your Main Inverter must have headroom and importantly must be a 2 way H BRIDGE design, and your batteries must have suffecient AH capacity to handle sudden surges.

However, you will need to control the back charging from your Mini Grid creating Inverter. Or else your batteries will cook. So energy management in this situation becomes very important.

If its just solar then its not difficult, if you have Wind turbines or Hydro, then things get complicated.

I only know of one comercial Inverter manufacturere that i have worked with that can handle AC coupling comfortably, but it still needs other protection limiters.

Davo99
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Posted: 08:19am 06 Aug 2022      

Sorry mate, Just talking about off grid ONLY. No AC coupling.

I just mentioned the AC because I have had the GTI's over paneled for years.

People say you cannot do the same with stand alone OFF grid inverters and can only have panel capacity as they specify on the machines and specifications.

I want to know with a purely off grid inverter and particularly and inverter charger type, If you can parallel more arrays  that are under the voltage limit but over the power limit they specify.

For instance, If an inverter Says  " Max PV array, 4000W"  Can I hook up 8 KW of panels providing I stay under the voltage limit, IE Multiple arrays that add up to 8000W
or will the inverter overload at anything beyond being conected to an array doing over 4000W?

Revlac

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Joined: 31/12/2016
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Posted: 10:24am 06 Aug 2022      

Davo,

I think they are covering there backsides.

It should handle more wattage, as long as the voltage is still within its limits, I haven't over panelled the old 5048MS that I have, but realised it was holding back due to some current limit setting, it was limited to 30amp or something, it would sneak over that limit for a few seconds but not long.
I opened it up to max after I found it, I would suggest limiting the current a bit if you are going to over panel it, give it a chance to throttle it back after a cloud passes, cloud edge affect.


You only need the extra panels for bad weather anyway.

Davo99
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Posted: 08:47am 07 Aug 2022      

I'm more thinking like My GTI's run, up early making good power till the sun gets some steam, stays pegged all day and mostly so even in winter and then still making good power till sundown.

Not about the peak power its about getting things going early and finishing late.
Over paneling and with split orientations seems to work well for my GTIS and would like to be able to do the same thing to get the most out of a an off grid type inverter.

Solar Mike
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Joined: 08/02/2015
Location: New Zealand
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Posted: 09:26am 07 Aug 2022      

Over paneling with split orientation is certainly the way to get even power throughout the whole day. Many of the more expensive PV charge controllers, whether stand alone or part of the inverter combo have user settings for max charge current; provided this option is present then battery charge current is clipped to the set value.
However many don't have this feature and wont work too well in an over paneled situation, they will just shutdown with excessive current. You will have to read their manuals carefully.

Cheers
Mike

Revlac

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Posted: 01:48am 09 Aug 2022      

Growatt SPF 5kW Single Phase Hybrid Solar Inverter - SPF 5000 ES
Is very similar to the MPP model (and others) with the  450v VOC solar input, and in the manual it says the "SPF 5000 ES: Default 60A, 10A~100A Settable" not sure if that is combined with another setting for that amperage.
Really need to find a manual to check each brand to see these options.

Davo99
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Posted: 09:59am 09 Aug 2022      

Is there a reason the amperage needs to be limited?

On my GTI's  I have hooked up 2KW more power from the panels  than the thing could use ( as evidenced by taking a 2kw input off the inverter and seeing it only drop less than 100W from flat out) and they are happy with that.

They only take what they need and the rest is ignored.

Is there a reason why battery inverter/ chargers would be different and why too much panelage  which was over amped but in voltage spec would cook them?

Pretty sure the GTI's have input specs as well but they don't seem to be hurt by the availability of more than what is specified.

As long as the VOC had come margin, the over wattage isn't going to push it to the inverter/ charger is it?  Won't it pull what it wants and that's it?

Just trying to understand facts and reality over the possibility of manufacturers guarding their butt.

Revlac

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Posted: 10:57am 09 Aug 2022      

Limiting the amperage is just a safety margin, to help avoid going over maximum, We don't know if they have any built in limits at or after there maximum, Maybe they do.

On the other hand it may not even get to the 100amp max due to the batteries not taking that much charge, taking into account the size and quality of the battery, they would be getting some nice steady charge early sunrise.

Solar power will be used to power the house loads before it charges the battery, once the battery is mostly or fully charged then the rest will be ignored same as the GTI's.

When charging the battery (I assume) these types of inverter charger run a converter (Transformer) backwards, then the square waves are rectified buy the set of mosfets to battery voltage, This is probably the part of the inverter that could be damaged. could be wrong and they might have changed that a little bit, I don't follow these much these days.


You might be ably to try it and find out, Try to negotiate a deal with a seller see if they will honer there warranty, replacement parts etc, You could tell them you will be running to its full solar input, don't mention going over spec, its on them if it don't work, you could probably negotiate a good deal.


There might be a way to use your other GTI's with this on a rainy day, grid connection would still be needed, will have to think about how that might work.
Edited 2022-08-09 20:59 by Revlac

Davo99
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Posted: 09:59am 10 Aug 2022      

Good point about the battery level and not taking the charge.
That said, one of the reasons I wanted to overclock them is so when I am using an appliance with high draw, I wanted the panels to be able to provide all the power possible to cover the load.

I notice the inverter chargers put out more than they will take in.

Also thinking today that an easy way around any problems might just be to use a seperate charge controller linked direct to the batteries.
That way I can have another 100 amps or whatever going in and that won't stress the main unit.

Might look at The MSB units as I think they have some Decent MPPT's.

Revlac

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Posted: 09:50am 11 Aug 2022      

Its always good to have another option in case of a failure (blown fuse or breaker while not home) to keep the place powered, so your not totally reliant on a single charger.
  Quote  Might look at The MSB units as I think they have some Decent MPPT's.

Search Didn't find them, do you have a link?

Davo99
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Posted: 05:30am 13 Aug 2022      

There are different Sizes but this would be probably what I'd go for.

They also have off grid inverters.  Was thinking about one of those as well.

https://makeskyblue.com/products/40a-mppt-solar-charge-controller?variant=20294126698558

There are others on fleabay but I don't know if any of them are any good at all.

Solar Mike
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Posted: 08:45am 13 Aug 2022      

That Make Sky Blue controller cannot be over paneled.... see their specs

Max input power
(The total power rated of PV can’t be over this watt that will break the controller.)


Other models like the Tracer model 6415AN series has the ability to limit output current to 60 amps and thus allow over paneling, costs a lot more though.

Cheers
Mike

Davo99
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Posted: 03:13pm 13 Aug 2022      

  Solar Mike said  
Max input power
(The total power rated of PV can’t be over this watt that will break the controller.)



This really is the Crux of what I was trying to find out.
My Delta inverter has much the same thing written in the manual. Max voltage, amperage and specified not to go over 6000W solar array.

Think is, I have had it running with DOUBLE the rating of the machine ( 5 Kw) for 5 years and I know for a time I had 12 Kw sitting on it and never had a problem.
All My other GTI's have been similarly over clocked and had no problems either.
according to the specs on the Delta at least, the thing should have long been in the scrap pile.

What I was hoping someone knowledgeable with the understanding of how these things work could tell me, if what was in the manual was just arse covering or if over paneling really would destroy them because they are built Different to GTI's?

Obviously not as straight forward a question as I assumed and I prefer not to find out the expensive way.

I over paneled the GTI's basically out of ignorance because I didn't realize the specs said don't so it so I was wondering if off grid inverters have some different working principal that allows them to cope with over paneling that a possible different setup in the circuity of an off grid inverter would destroy it?

Maybe the question I should be asking is If I over panel one of these and claim warranty, how could they tell what I had done rather than just a component failure caused by something else?   :0)

Revlac

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Posted: 10:44am 14 Aug 2022      

I expect the Make sky blue mppt controls the charge by sensing the battery voltage, when the battery voltage is close to its full charge voltage it will back off the charge current as it should, it probably has no idea how many amps are available if it is over panelled, if the battery is low, it could just ramp up until something fails, Thats my guess,
Someone correct me if I'm wrong
they have other MPPT's that do a lot more and more price as well, haven't looked into them.

Other mppt's that have current limit settings, should keep within those settings even when over panelled by 30% (self preservation) it should easily accommodate for inverter load while charging......Keep in mind, a with a fully charged battery and the inverter using 2Kw or 4kw and the load is suddenly taken off, the charge controller MUST also back off quickly, or could result in (overshoot) over voltage to the battery and all connected to it, Had that happen when running on 2 sets of truck batteries (8 in total), luckily the MPPT went into fault and disconnected, reconnected itself soon after.

As far as warranty goes, not sure about MSB cant find any information.

Growatt had a 2 year warranty on some of there inverters, repairs go back to there service centre, so they might find out if it has been over powered.

MPP, had a 1 year warranty last I looked, the inverter was too costly (shipping weight) to ship back for repairs, so the user was asked what happened, the fault code, to open the case and do an inspection, take some photos, then receive a component checklist and test associated parts with a meter if possibly, then report back to them.
There engineer would look at the results, end result they sent out a new main board to be installed, may have to pay shipping
Done this once.
This has apparently become a more difficult process since, now they have a local dealer they probably get shipped back to that service centre, I don't know, so they might work out what happened.


I intend to over panel the system I have perhaps 30% or something, panels are not putting out the full rating anyway.

The simple solution most people have done is to add another charge controller when its needed.

I started off grid, by Buying off the shelf gear, have since learned a lot, I don't want to buy this stuff anymore, its a lot more expensive now, prefer to build the gear with the help and knowledge of the forum.

15 years ago the amount of 48V inverters around, you could count on one hand, now they are everywhere.
Edited 2022-08-14 20:46 by Revlac