Growatt - Odd behavior

[debron55]

I have no experience with the MPP all-in-ones, other than that they seem often to be referred to in the same breath as the Growatts. My gut tells me that they are very similar units with different firmware and possibly different construction quality. Considering that the comparable MPP units have "Support lead acid and compatible LiFePo4 batteries" in the feature list, I personally wouldn't expect them to be much different.

With regard to your question about compatible batteries, I would think that you would be looking at the Lithium setting on the Growatt, rather than USE2. The latter appears to be for lithium batteries without a BMS, thus the behavior you dislike. But don't take my word for it.

Recommended float charge settings seem to be in the range of 27.2 to 27.6, based on the sticky post here and my battery manufacturers recommendations. I would think anything between those two numbers should be fine.

Thanks for the response - Lithium setting on the growatt is only for use of THEIR battery - it has a comunications wire that plugs into the growatt.

 

[fazeshift]

so in the ongoing conversation with Growatt this is the latest response.



Hello George,

The system for US2 is working as needed. As the lithium battery without a BMS, if you need to use solar power during the battery voltage is full, please ask the battery supplier to integrate the BMS of the inverter into the battery to make sure the BMS of the battery is compatible with the inverter.

Best
Kevin L


I would note that in my multiple responses they are aware that the system batteries have Overkill Solar BMS. Now that's probably not what they want as I have no way of knowing if overkill solar BMS (https://www.resacs.cz/user/related_files/8s-100a-6.pdf) will integrate with or communicate with the Growatt. I suspect not at this time. Who knows about the future. But I would also note - at no time have they challenged my observations or understanding of the US2 settings impact (solar power clipping off as batteries reach a full charge as indicated by setting 19).

I'm not terribly sure what else to do other than use setting USE since it appears to work. hopefully it isn't doing any damage to the LifePo4 cells - I don't know how it could be but I'm not a solar or battery engineer. The BMS' are not locking the battery down IE they are not going overvolt on cells or pack. And at least seemingly the unit charges the batteries and then powers the load from the panels if in use mode. You know like you'd expect a solar inverter to do. Not so much in us2 (which Growatt tech seems to be intent on us using). I mean if the thing is just going to shut off the solar in the middle of the day isn't it really just a acting like a solar Charge controller and a battery powered inverter in one box.. a solar inverter that shuts off solar panels halfway through the day is not, in my opinion, very useful. I would be interested if this behavior is seen in any of the other "all in one" s...

I've been watching this thread, and suspected this was going to be their response.

I am curious what you happen if you responded with something like: "My battery supplier is interested in making their BMS compatible with the Growatt inverter. They asked for documentation of the communication protocol - could you please provide? Thanks."

I would be interested to see that documentation. Hardware that can speak RS485 is cheap, and relatively simple to engineer. I know that doesn't directly resolve the issue here, but I'd love to build something that connects between the Growatt and BMS (Overkill already has documentation on its TTL UART interface, has Arduino libraries, etc.)

 

[SiliconOrb]

Lithium setting on the growatt is only for use of THEIR battery - it has a comunications wire that plugs into the growatt.

Yes, this is understood. My comment was regarding the question you posed to the Growatt:

"Is there currently a battery on the market that works with growatt in the use2 setting? Like who makes a BMS that does that?"

My understanding of the USE2 setting is that it is intended for a lithium battery which does not have a BMS. So technically, all batteries on the market "work" with it, just not in the manner you desire. A BMS will likely not change that fact, unless it is one which is compatible with the unit's Lithium battery setting, which would then be used instead of USE2.

 

[robby]

Following along with this issue. Growatt needs to fix it fast.

 

[Zwy]

Following along with this issue. Growatt needs to fix it fast.

The fix is to follow the settings that were listed and USE, not USE2.

 

[robby]

The fix is to follow the settings that were listed and USE, not USE2.

That does not seem like a real fix to me. Using Lead Acid charging parameters for Lithium seems like a bandaid fix!
I am not at all familiar with the Growatt but I would think that in an open loop system they would have the user input the capacity of the battery and then monitor the input and output current and use those to get a fairly accurate picture of the SOC at any point in time. I don't own a Growatt so if the owners are happy with the USE1 fix then who am I to argue.

 

[SiliconOrb]

That does not seem like a real fix to me. Using Lead Acid charging parameters for Lithium seems like a bandaid fix!
I am not at all familiar with the Growatt but I would think that in an open loop system they would have the user input the capacity of the battery and then monitor the input and output current and use those to get a fairly accurate picture of the SOC at any point in time.

The focus of this type of unit seems to be convenience, simplicity and price. For the most part, it achieves those goals. To put things into perspective, it cost less than half of only one of the two smart LiFePo4 batteries I have in my system. My only real complaint stemming from the off-loading of more complete battery management is not being able to remotely monitor the actual SOC and have it included in the statistics.

With this unit, I would have serious reservations about using unsupported lithium batteries which lacked comprehensive built-in protection. But at least in my case, it does what it needs to, without making me pay for redundant features. It's not going to be a great choice for every use case, but I'm pleased that it exists.

What you suggested would be a welcome additional feature in order to get a more accurate "ball-park" figure for SOC. I just don't know that it would be very useful for charging algorithm decision making. Just knowing the true capacity of the batteries is something which would be limited to enthusiasts, and I don't think too many enthusiasts are opting for this type of system. Then there are the issues of compounding error and things like heated batteries, differing BMSes, poor battery health, etc. where a portion of the current used by the batteries isn't actually being stored.

 

[Zwy]

That does not seem like a real fix to me. Using Lead Acid charging parameters for Lithium seems like a bandaid fix!

Those are not lead acid charging parameters.

I am not at all familiar with the Growatt but I would think that in an open loop system they would have the user input the capacity of the battery and then monitor the input and output current and use those to get a fairly accurate picture of the SOC at any point in time. I don't own a Growatt so if the owners are happy with the USE1 fix then who am I to argue.

Please list all the units out there that are completely integrated between a battery BMS and the charge controller and communicate with each other.

You have that option with GW by purchasing their battery. People choose not to and instead opt for their own battery bank. The GW allows custom settings for this purpose. I don't see the problem.

 

[robby]

Those are not lead acid charging parameters.


Please list all the units out there that are completely integrated between a battery BMS and the charge controller and communicate with each other.

You have that option with GW by purchasing their battery. People choose not to and instead opt for their own battery bank. The GW allows custom settings for this purpose. I don't see the problem.

All the Sol-Ark units and so is Schnieder 6848 completely integrated in a closed loop system with various batteries like Fortress and Simpliphi batteries. Plus other battery companies are joining in this year.

Even their method of dealing with open loop systems is very good at determining SOC just based on information provided by the user and doing one full power cycle.

 

[debron55]

I mean here's the thing. This unit requires a battery to function. And I find it difficult to believe that the company Growatt doesn't know that a great great many of folks building systems using this unit are using LifePO4 batteries. The USE setting was for lifepo4, then they added another one called us2. It's also for lifepo4. THere's already dedicated flooded / lead / agm setting. and there is a factory growatt lithium setting that communicates with the bms. It seems to me a bms only knows the same things the growatt unit knows. The bms knows the Voltage of the overall pack and the Voltage of individual cells. All of the energy it gets or sends out is through the all in one unit. so what more does the bms know that the growatt doesn't? I would add... that there is no US distributor of Growatt batteries that I easily located (with the caveat I only spent a few minutes with google search). But importantly - the key issue. If using a lifepo4 battery (made by us or sold by BattleBorn etc) results in the system shutting off the solar panels at any time and not using them for powering the load thats a problem. Now I got around it by using the old use setting but growatt seems committed to me using us2. so there is a significant disconnect. I would also add - how does MPP handle this. I mean I would think if MPP was doing this I'd have seen references to it in my days and days of searching. I dunno.. at least right now it's working for me. But I'm not particularly pleased with the whole thing.. Just the lack of transparency from Growatt about what the expectations are regarding using the system with your own lifePO4.

 

[Lt.Dan]

The BMS knows individual cell voltages, so if it notices that one cell is running (high voltage), it will communicate with the Growatt (or MPP) and tell it to slow down the charge process to a point where the balancer can keep up with the charging, therefore, the battery never gets out of balance because the BMS and the inverter are able to communicate. Its quite brilliant actually.

Idk what the Growatt batteries are, but MPP is compatible with several different brands, Pylontech i think being the most common, and you can find them on Alibaba etc for a decent price. $0.25-0.30 per watt.

My LV6548 does not have a USE2 option, only USE, which works flawlessly and never does what is being talked about in this thread. So idk how MPP has figured it out, but Growatt hasnt? Why is Growatt so insistent on you using USE2 if USE does exactly what you want? Ignore them and do what you want. It's your inverter in the end.

 

[jrscarlett]

Growatt could support many 3rd party battery management systems with a firmware update and an RS485 to Bluetooth Adapter. I would happily buy that extra layer of protection if they sold it. I would probably try to build it if there was any documentation on it. For now, using the USE setting is the best option for my setup.

 

[Dsiee]

Wrong thread, sorry.

 

[Redlightning]

my setting are both at 58v and it still will not start back charging untill my Batt. are very low. some times not untill the next day had to put a out back Flex 80 to help its better but my 24 volt system with 2 outback Flex 80's starts recharging as soon as a load draws on my Batt. I dont get it there is alot of confusion on this issue.

 

[Redlightning]

What voltage have you observed MPPT charging stopping and what voltage is it resuming? How many watt-hrs of load are then supplied by battery in the time between stop and resumption of charge and what percentage of your total energy storage does this represent?

The charging behavior you are observing appears normal for Growatt, what is unclear is if the trigger for resuming charge is simply a voltage drop below setting 19 or 20, or drop in SOC , or some combination of factors.

Yes it would be nice if when setting 14 is set to OSO, (solar charging only), MPPT charging remained active as long as solar was available, but this behavior does not result in a material reduction in energy harvest or overall system performance, at least not on my system. Not suggesting that is the case for everyone, but on most days my system has to curtail charging as PV input far exceeds load demand so its not like I am loosing significant energy harvest..

OSO, (solar charging only), MPPT charging remained active as long as solar was available this does not work on these tried this setting still stops charging.

 

[snoobler]

my setting are both at 58v and it still will not start back charging untill my Batt. are very low. some times not untill the next day had to put a out back Flex 80 to help its better but my 24 volt system with 2 outback Flex 80's starts recharging as soon as a load draws on my Batt. I dont get it there is alot of confusion on this issue.

Have you tried a float voltage of 27.2V? Contrary to BigBattery's data sheet, you should not have float set to 58.

Have you attempted a reset? Power switch off, disconnect PV, disconnect battery, connect battery, connect PV, power on?

What you've described across multiple threads seems somewhat common, and a reset generally seems to improve the performance.

 

[Redlightning]

yes but it still keeps happening and I cant do a reset every day what is also strange is the flex 80 acts a little different on the 48v system verse the 24v system

 

[snoobler]

yes but it still keeps happening and I cant do a reset every day what is also strange is the flex 80 acts a little different on the 48v system verse the 24v system

What about your float voltage? Have you set to 27.2V, reset the unit and confirmed errant behavior?

Your FM80 cost almost as much as your Growatt, right? I'll let you draw your own conclusions.

Assuming you bought this from Ian at Watts247.com, have you brought this to his attention? He should replace the unit if it's still in the warranty period. If you bought it elsewhere or are not in the States, sorry.

 

[Redlightning]

yes I did I bought 4 units

 

[snoobler]

yes I did I bought 4 units

Excellent. What did Ian say?

Are all 4 units exhibiting this behavior?

And again, what about your float voltage?

 

[jrscarlett]

I found for my growatt SFP 6000T DVM-MPV that Battery Type = USE and setting Floating charging voltage close to Bulk charging voltage seems to give the behavior I wanted. With these settings, my inverter system starts recharging the batteries at float value and stops at the bulk.

US2 was completely useless (for me and some others here) and I noticed yesterday that it has been removed from the latest version of the manual for my unit (Version 1.1 SFP 4000T - 12000 DVM-MPV). What you describe sounds like the US2 behavior I experienced.

Note: I'm grid charging only with currently no PV (UPS mode with Utility passthrough)

 

[snoobler]

I found for my growatt SFP 6000T DVM-MPV that Battery Type = USE and setting Floating charging voltage close to Bulk charging voltage seems to give the behavior I wanted. With these settings, my inverter system starts recharging the batteries at float value and stops at the bulk.

US2 was completely useless (for me and some others here) and I noticed yesterday that it has been removed from the latest version of the manual for my unit (Version 1.1 SFP 4000T - 12000 DVM-MPV). What you describe sounds like the US2 behavior I experienced.

Note: I'm grid charging only with currently no PV (UPS mode with Utility passthrough)

You are talking about a completely different issue. The Growatt has a goofy AC charger and has nothing to do with PV charging parameters/performance.

Growatt AC charger turns on at the low voltage and stops immediately upon attaining peak voltage. It does not have bulk/absorption set points but simple on/off voltages.

In order to have your unit function as a useful UPS, you would have to set both values to nearly the same number, and the "on" value should be at the float voltage of the particular battery.

 

[jrscarlett]

Hence the note Grid Charging, main point is US2 is not doing what the manual leads you to believe with an LFP battery.

If you have not done it install the Xiaoxiang BMS on your Phone (IOS or Android) to see what is going on inside the BigBattery. I'm guessing 58V is shutting it down as just because growatt thinks it's connected to 58v it could be up to 1V more or less (alternatively it could be growatt side with a fault code 3 overcharge if you are not connected via shineserver). Voltage calibration can be adjusted on these units if you know which one is correct (BMS hopefully).

For example, my BigBattery Husky BMS is set from the factory at full voltage at 55.2V (got to pay to see/configure that in the app) and differs from the growatt reading by 0.8V.

 

[Redlightning]

I did not contact them un till you suggested it I guess1 im a dumb ass at times I am a diesel mech. there are alot of things i can not understand when it comes to solar but I am trying

 

[snoobler]

I did not contact them un till you suggested it I guess1 im a dumb ass at times I am a diesel mech. there are alot of things i can not understand when it comes to solar but I am trying

You tried to solve your own problem. Not a bad trait.

Please let us know what Ian says.