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24v 3kW Inverter recommendation


Spys

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Hi

I recently moved from a Mecer 24v 2400w inverter to a Growatt SPF 3000 TL HVM-24 3kW 24v inverter. 
 

I am using the Growatt with 2 x 12v LiFePO4 batteries. No BMS integration with the Growatt. 
 

I am less than impressed with the Growatt and want to replace it. 
 

What is the best 24v inverter in +-3kW size? Are there any non Axpert based options?

 

Many thanks

Peterr

 

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1 hour ago, Spys said:

Hi

I recently moved from a Mecer 24v 2400w inverter to a Growatt SPF 3000 TL HVM-24 3kW 24v inverter. 
 

I am using the Growatt with 2 x 12v LiFePO4 batteries. No BMS integration with the Growatt. 
 

I am less than impressed with the Growatt and want to replace it. 
 

What is the best 24v inverter in +-3kW size? Are there any non Axpert based options?

 

Many thanks

Peterr

 

Although Axpert based they seem to be far superior to Axpert/Mecer on paper. 

From all the different off grid inverters I have come across in 24V the Phocos seems to have the best specs. It is termed Any-grid as it can function without a battery and blend PV with grid. Up to 5000W PV of which 4000W can be produced and 2400W can be used for battery charging.

Check it out. Also the only 3kW that you can run inverters in parallel that I have read about.

IMG_20230102_231059.thumb.jpg.f956cc162923b33956e5ef7e28041604.jpg

Edited by Scorp007
Added Phocos specs.
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10 hours ago, Spys said:

I recently moved from a Mecer 24v 2400w inverter to a Growatt SPF 3000 TL HVM-24 3kW 24v inverter. 
I am using the Growatt with 2 x 12v LiFePO4 batteries. No BMS integration with the Growatt. 
What is the best 24v inverter in +-3kW size? Are there any non Axpert based options?

Hey Peter, I hope you don't mind me asking, is there a reason you want to avoid Axpert and what about the Growatt was so bad you want to replace it?

So finding a 3kW inverter with BMS would be tough, because of the 24V nature of the unit they are designed for AGM/Gel since Li-12V batteries aren't very common and often end up being too expensive but you can always integrate your own BMS.

Otherwise, if you can find a decent Axpert from a good/trustworthy supplier it should perform like a dream. However, that depends on why you aren't happy with the Growatt

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1 hour ago, Psy said:

Hey Peter, I hope you don't mind me asking, is there a reason you want to avoid Axpert and what about the Growatt was so bad you want to replace it?

So finding a 3kW inverter with BMS would be tough, because of the 24V nature of the unit they are designed for AGM/Gel since Li-12V batteries aren't very common and often end up being too expensive but you can always integrate your own BMS.

Otherwise, if you can find a decent Axpert from a good/trustworthy supplier it should perform like a dream. However, that depends on why you aren't happy with the Growatt

Hi Psy

 

Grab a cup of coffee / beer, this could take a while😀

 

So up until about 2 months ago, I had a very simple system using a Mecer 2400w 24v modified sinewave inverter, connected to 2 x 12v AGM batteries. It powered various plug points around the house which provided us with backup power during loadsheeding for internet, TV, cellphone chargers etc. Nothing hectic. Batteries would last about 10 hours. Once stage 4+ load shedding started hitting Durban again I noticed the batteries wouldn't make it through the 2 hour loadshedding. I set out to simply buy two more AGM's (I was aware of LiFePO4 and the benefits, but scared of the cost plus it would have meant an inverter upgrade so more $$$). I went to the regular battery/power shop that I deal with, long story short ..  they had some freestanding 12v 100ah LiFePO4 batteries at a reasonable price (R6k each). Brand new, sealed in the box, first life.( Specs attached). They assured me that as long as I kept the Mecer at 10A charge setting I could use them as a direct replacement. The batteries have a built in BMS that would control the charging etc.

 

So I took the leap of faith and was massively impressed. They just ran and ran and ran (based on my load). I added a Hubble lithium battery equalizer that would keep the batteries balanced but via the Bluetooth and app gave me some visibility into the actual battery charge state. Each battery would charge up to about 14.33V and then settle at about 13.7V. With my limited knowledge and online reading this seemed reasonable and inline with expectations.

 

Everything was so lekker that I started to get ambitious. I called in my electrician and we split the DB into essential and non-essential workloads. With everything possibly load I could think of we hit a peak of 3.5A on the non essential side. This covered every plug point, light (inside an out) etc. It was agreed that to do this properly I would now need to upgrade the inverter to something better. Pure Sinewave, stay with 24v due to the recent battery investment, 3kW would be plenty based on my max load. Everything would now be installed properly, move the inverter out the house and into an outbuilding, install a sub-DB with failover switch, DC disconnector etc.

Doing the usual online research, reading, my budget, local support etc. I originally settled on and ordered a Kodak OG 3.24. A week later the online supplier (well known/reputable) say ooops we don't actually have the stock and no new stock until January 2023. They did have stock of the Growatt bundled with the WiFi module at a reasonable price. The Growatt had been on my original list so I settled on this.

The purpose of my system was always to provide backup power during loadshedding, not as a electricity cost saving exercise. So solar was a potential future add-on to provide battery charging during daylight hours and backup power for the essential load in the event of a prolonged outage due to faults etc.

 

Everything was purchased and installed. Plugs around the house have been split into Red (Essential on inverter) and white (non-essential) so as to limit mistakes in people/contractors plugging into the wrong sockets. As there is no battery BMS to Growatt integration, setting were set up manually. The key ones being:

1 - set to Uti - Utility First

2 -maximum charging current set to 20A

3 - UPS 

5 - US2 - user defined for Lithium without BMS communication)

10 - 2 batteries in series

11 - 20V - maximum utility charging

19 - 29.2V

20 - 29.2V (with the US2 battery setting 19 & 20 and linked)

21 - 22V

 

For items 19, 20 & 21 I have tried multiple options, settings and combinations with almost always the same result.

 

So if we look at image battery graph 1, this is a 28 day view. On the left this is whilst still running on the old Mecer inverter, happily charging up to 14.2v per battery and then settling at about 13.7V (27.4v). And it would happily sit at these levels until the next loadshed.

The Growatt was installed about 15 December.

So what is the problem or at least what is it that I perceive is the problem?

On the Growatt I noticed it will charge to about 27V but then settle down to about 26V. No matter what settings I use, always the same result. I know it isn't (or shouldn't be) the battery BMS limiting charge as it allowed and held more charge on the Mecer. Then on the 19 December, the big dip, the Growatt had a melt down, through out errors 19 and 4 if I remember correctly and showed the batteries had instantly depleted. Only way I was able to resolve this was to do an full reset include EEPROM reset. This got everything back online. As you follow the graph you will see a gradually lower SOC for the batteries, but everything worked.

 

At this point I had settled on the fact that 26V was where the Growatt was happy and as long as it worked, stop analysing the information and let it be. Then on the night/morning of 29/30 Dec we had loadshedding from 12am-2am. The system stayed up for 2 minutes then immediately shutdown claiming the batteries were flat. By the morning everything was recharged. I cut the mains power to test and everything stayed up and worked perfectly. I ran it for 4 hours like this and no problems. I even forced the load up to 1.4kW for 2 hours, no issues and very little battery drain.

 

I stopped in at the battery supplier to chat about the problem. A suggestion was to hook up the batteries to the Mecer again and see what happens. I did this yesterday .. image graph 2 which is a 24hr view. You can see the immediate increase in SOC. After reaching full charge on the Mecer I left it for a few hours. Everything looked good. I then cut it back over the the Growatt and the SOC levels were held for the night. At 6:55am this morning, whilst still on full grid/mains power the SOC level drops down to 26v again and now is just sitting there.

I also see strange anomalies on the ShinePhone app where it is showing PPV power input (image attached) even though I have no solar panels or anything attached.

 

So the way I see it, in my very simply uneducated assessment, it I have two options. 1) Buy a better battery like a Hubble AM-4 which will offer BMS communication integration and take the battery charging, SOC though process away from the Growatt 2) Buy a different/better quality inverter that will manage my existing batteries better.

 

Option 2 is half the price of option 1, and thus my question on this forum. My twitch about Axpert is that reading on the various forums there are as many unhappy Axpert users trying to deal with things like the premature float bug. The Growatt is a variance of the Axpert type device, supposedly one of the better ones ? 

 

I don't have 48v or Victron type money so I was looking for better than "Axpert" but cheaper than Victron. The Holy Grail.

 

I know my testing via connecting up the Mecer again is far from accurate or scientific but it seemed to give me a quick answer that it isn't the batteries?

 

Thanks
Peter

 

 

Battery Specs.PNG

Battery graph 1.jpg

Battery graph 2.jpg

growatt ShinePhone Image 1.PNG

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Just two more images showing the install in case there is anything obvious.

On the ShinePhone app I also see information I would not expect, such as the massive Export to Grid statistic given that I am not exporting to grid if I understand things correctly.

 

 

 

Install 2.png

Install 1.png

ShinePhone image.PNG

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8 minutes ago, Spys said:

So I took the leap of faith and was massively impressed. They just ran and ran and ran (based on my load). I added a Hubble lithium battery equalizer that would keep the batteries balanced but via the Bluetooth and app gave me some visibility into the actual battery charge state. Each battery would charge up to about 14.33V and then settle at about 13.7V. With my limited knowledge and online reading this seemed reasonable and inline with expectations.

This is correct, your bulk charge will usually head up to 14,3V before reducing back down to float. 13,7V float is great and what you would expect to see. As long as they're returning to about 13,5V float then you are on track. On the brighter side the Growatt won't damage your batteries, LiFePO4 batteries are more than happy to keep on keeping on with a charge cycle between 30%-90%. Lithium can handle not being fully charged and it shouldn't cause issues, so I cannot imagine why it ran flat...

Because I am not used to working with Growatt, there are a few things I don't know that hopefully someone else will have the exact answers. But, it looks like your charge voltages need adjusting. Now many inverters need to be in "Stand by" (Unit is on but not producing output) mode in order to change certain settings, so that could be an issue. It could also be a "Back to charge" or "Charge when grid is available" setting that is incorrect. Just go through, often a silly setting like that can be missed completely messing with the charge cycles etc.

Otherwise, most of these inverters that do not have BMS use a voltage monitor to manage the batteries. These voltmeters come with a +-20% accuracy and it is possible the Growatt is reading a little off and is thus not charging. Does your feedback from the inverter match the data provided by the Hubble balancer?

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@PsyThanks for replying.

 

I have tried a bit of fiddling with the voltage point back to utility and voltage point back to battery options as a "just in case" but I have largely ignored them as they are supposed to only apply to SBU Priority or Solar First settings in field 1. As I am running Utility first without solar I have assumed that these two options are "not active".

 

Generally the battery voltage readings on the Growatt and the Hubble balancer are within 0.02v of each other so no issue there. Expect when the Growatt says the batteries are depleted and goes off line and the Hubble still shows 13.xxv per battery available.

 

I'm at the limit of my trouble shooting abilities and also a little fed up that something that costs 4x the price of the Mecer is less stable and less effective. 

 

 

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You're welcome, always happy to help in any way I can and wish I had more concrete help for you. Yeah at this point we need someone more familiar with Growatt to advise, there may be something small causing your issues but as mentioned my experience with these is minimal at best... I work with Axperts a lot but haven't had a chance to play with Growatt.

Oh and fyi, just in case you didn't know, the Macer 3kW is just another Axpert... There are a couple companies like MCE Electrical that may have units available, the performance is like 1-to-1 and at least places like that will help you if you have any issues with the unit.

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3 hours ago, Spys said:

As there is no battery BMS to Growatt integration, setting were set up manually.

With my Growatt I do a once a month voltage charge as the Li Protocol causes a drift down of battery voltages over time.
US2 mode has never worked the way I wanted. I use the USE mode and set the voltages manually. US2 acts the same as the LI Protocol and the batteries also drift down over time.

So all I can suggest is to try with USE mode without any BMS comms cable for a test. It works well in my off-grid setup. I am on Solar only.
Set your voltages and charge rate as per your battery specs. And do restart the Inverter after you have activated the USE mode. After restart recheck that all your settings are still as you want them.

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There is also a hidden menu set that no official documentation of Growatt discloses. This one was posted by a user some time ago. There may be more but only the insiders will have that info I suppose.
Maybe you can check what your factory Battery voltage offset is set to. Don't change anything there, just check. I changed mine and in Li Protocol it causes some really strange Inverter behaviour in the Li Protocol charge rate where it just sets the charge rate to 0Amps and all charge stops. It is a bug but I have no intention of arguing with their rep about it because the normal user is not supposed to know about it.

If you press the up and down button simultaneously a new menu opens with three zeros, i.e. 000
Use the select button (right hand button) to cycle through the three digits and set them all to 1, i.e. 111
When you then enter that a new menu opens with some offsets and other menu items that I am not even sure what they really do, but the second item down is in this submenu is a Battery offset voltage. Mine is factory default +0.5V.
This I figured out causes the Inverter reported battery voltage to report about 0,5 to 0,8V higher voltage than the battery itself, which I suspect is part of the problem why the battery never really gets charged fully. I have the suspicion it is actually the charge voltage itself and not the actual battery voltage. As said, changing this in LI Protocol causes the Inverter to stop charging.
In USE mode I can and have changed it and after months of fiddling I found that at -0,1V offset that I can now charge the battery to specs and the Inverter and Battery will agree at last as to what the Battery voltage is.
Below a sequence of photos of how to get to this hidden menu.
This is what comes up when you hold in the up and down arrow keys simultaneously
image.thumb.png.1cea57d20de71ca17d8d2917fa6d5b91.png

Then enter 111 

image.thumb.png.dd6368f5fe31e27c5de598d6c22946c2.png

Next is the first menu item that comes up, which allows grid offset as far as I can establish. I don't have grid connection, so it's irrelevant

image.thumb.png.242aa8d69491e8af2eabc2350fc3fde4.png

One menu item down then brings you to the battery offset. Have a look what yours shows.

I'll have top attach the last photo separately as there is a 3mb limit.


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5 hours ago, zsde said:

With my Growatt I do a once a month voltage charge as the Li Protocol causes a drift down of battery voltages over time.
US2 mode has never worked the way I wanted. I use the USE mode and set the voltages manually. US2 acts the same as the LI Protocol and the batteries also drift down over time.

So all I can suggest is to try with USE mode without any BMS comms cable for a test. It works well in my off-grid setup. I am on Solar only.
Set your voltages and charge rate as per your battery specs. And do restart the Inverter after you have activated the USE mode. After restart recheck that all your settings are still as you want them.

Thanks zsde. It’s this continual type of maintenance that I want to avoid. 

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