Growatt - Odd behavior

jkoprowski

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Please help me out if I am missing something. The cheap Alibaba sourced BMS's have some features like low temp, high temp, high current, etc. However, how would a BMS since it is looking at each cell offer cell-level protection when working with a growwatt? Let's say a cell reaches low SOC slightly before the rest of the cells in the pack. How would your BMS tell the inverter to stop inverting? Or, lets say one cell reaches its top of charge limit before reaching the set pack voltage in the growwatt MPPT? Does the BMS just cut the connection at that point? And wouldn't that be detrimental to the growwatt if the BMS disconnected the battery bank while charging from a large PV array? sorry if I am confused, I am just used to working with victron equipment that has a direct link with your BMS, it controls charging and discharging from the BMS at a cell level (either by the remote or canbus). How does growwatt do this, from what I am reading all that growwatt is concerned about is pack voltage... thanks ahead of time guys
 

Zwy

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Please help me out if I am missing something. The cheap Alibaba sourced BMS's have some features like low temp, high temp, high current, etc. However, how would a BMS since it is looking at each cell offer cell-level protection when working with a growwatt? Let's say a cell reaches low SOC slightly before the rest of the cells in the pack. How would your BMS tell the inverter to stop inverting? Or, lets say one cell reaches its top of charge limit before reaching the set pack voltage in the growwatt MPPT? Does the BMS just cut the connection at that point? And wouldn't that be detrimental to the growwatt if the BMS disconnected the battery bank while charging from a large PV array? sorry if I am confused, I am just used to working with victron equipment that has a direct link with your BMS, it controls charging and discharging from the BMS at a cell level (either by the remote or canbus). How does growwatt do this, from what I am reading all that growwatt is concerned about is pack voltage... thanks ahead of time guys
If you make the settings in both the BMS and GW conservative for longer cell life, it really becomes a mute point concerning comm between BMS and GW. You just won't hit those fringes.

Now, if you want to run all the way to 3.65V per cell down to 2.5V per cell using commodity cells, you will find hours of frustration and shortened cell life. Doesn't matter if you use Victron or another system with full comm between BMS and inverter/charger.

Those few Ah's you will gain are not worth it. You're talking maybe 3 to 5 Ah's once you're into a knee area.
 

coolbz

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If you make the settings in both the BMS and GW conservative for longer cell life, it really becomes a mute point concerning comm between BMS and GW. You just won't hit those fringes.

Now, if you want to run all the way to 3.65V per cell down to 2.5V per cell using commodity cells, you will find hours of frustration and shortened cell life. Doesn't matter if you use Victron or another system with full comm between BMS and inverter/charger.

Those few Ah's you will gain are not worth it. You're talking maybe 3 to 5 Ah's once you're into a knee area.
If battery charge settings in GW are more conservative than battery BMS parameters, shouldn't GW charge and discharge battery without BMS intervention? If so, the original issue should not happen. Is that right?

BTW, I just bought 3000TL LVM-ES system with Santan panels and having them setup without battery. My goal to to use as much solar energy at day time and fall back to grid seamlessly when solar is low. I plan to add battery when price and reliability improves in the future.
 

Zwy

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If battery charge settings in GW are more conservative than battery BMS parameters, shouldn't GW charge and discharge battery without BMS intervention? If so, the original issue should not happen. Is that right?

GW settings will protect the overall battery but not on cell level. As these are commodity cells, you will always have runners at both the high end of charge and low end of charge. The BMS will protect those cells.

The BMS is the final protection. However if you abuse it, it will fail.

BTW, I just bought 3000TL LVM-ES system with Santan panels and having them setup without battery. My goal to to use as much solar energy at day time and fall back to grid seamlessly when solar is low. I plan to add battery when price and reliability improves in the future.
ES is battery less capable, isn't it?
 

coolbz

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GW settings will protect the overall battery but not on cell level. As these are commodity cells, you will always have runners at both the high end of charge and low end of charge. The BMS will protect those cells.

The BMS is the final protection. However if you abuse it, it will fail.


ES is battery less capable, isn't it?
Thanks for sharing knowledge of different protection levels between charger and BMS!

Yes, ES is able to run without battery.
 

iSwannie

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Hi gentleman,

I have enjoyed this thread for it has a lot of good information for beginners. I am also experiencing at times my batteries (LifePO4) on my 48v Growatt picks up load during the day. To me the sun should carry this while it is available. I posted a screenshot of my Growatt and verified I am using the USE setting. Thank you all for your input and recommendations.

iSwannie
 

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Zwy

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Hi gentleman,

I have enjoyed this thread for it has a lot of good information for beginners. I am also experiencing at times my batteries (LifePO4) on my 48v Growatt picks up load during the day. To me the sun should carry this while it is available. I posted a screenshot of my Growatt and verified I am using the USE setting. Thank you all for your input and recommendations.

iSwannie
What are bulk and float charge settings? Moving float up closer to bulk will keep the CC powering the loads after full charge of battery is reached. I have my GW set for 28.0V bulk and 27.5V float.
 

iSwannie

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This morning the sun is charging the battery and carrying the load just fine. We will see what happens once the battery gets charged between 1:00 and 2:00PM to see if we can repeat what I saw yesterday with the battery taking some of the load while the sun should have carried it all.
 

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iSwannie

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All,

I have only been studying and playing with the solar concepts for about 6 months so please feel free to critic as required. After further analysis and looking at the results in more detail on my system I believe what appears to be happening is the Growatt 48v SPF 3000TL MPPT is responding too slow and the batteries have to make up the difference when the load moves around. I would love to hear your thoughts on this! See attached screenshot of my system for today.
 

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coolbz

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All,

I have only been studying and playing with the solar concepts for about 6 months so please feel free to critic as required. After further analysis and looking at the results in more detail on my system I believe what appears to be happening is the Growatt 48v SPF 3000TL MPPT is responding too slow and the batteries have to make up the difference when the load moves around. I would love to hear your thoughts on this! See attached screenshot of my system for today.
The chart looks beautiful! No grid power usage is needed. When sun power goes up, it supports your load and probably charging battery as well. Maybe the solar power line is not 100% accurate, so it did dip below your load and then battery power comes in briefly. I'm testing and setting up a similar system at home to support as much load as possible through solar.
 

Zwy

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All,

I have only been studying and playing with the solar concepts for about 6 months so please feel free to critic as required. After further analysis and looking at the results in more detail on my system I believe what appears to be happening is the Growatt 48v SPF 3000TL MPPT is responding too slow and the batteries have to make up the difference when the load moves around. I would love to hear your thoughts on this! See attached screenshot of my system for today.
Could be clouds. It looks good to me except it seems the GW pulled some grid power?
 

coolbz

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All,

I have only been studying and playing with the solar concepts for about 6 months so please feel free to critic as required. After further analysis and looking at the results in more detail on my system I believe what appears to be happening is the Growatt 48v SPF 3000TL MPPT is responding too slow and the batteries have to make up the difference when the load moves around. I would love to hear your thoughts on this! See attached screenshot of my system for today.
Is your chart generated from Growatt's PC software that pull data through USB connection? And in your load, do you have large appliance, for example refrigerator, dishwasher, etc maybe around 1kw? I'm curious of how well their 3kw system handle large load?
 

iSwannie

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1. Yes I use the wifi dongle and their website provides the data feed.
2. Yes, all my computer equipment, freezer, refrigerator, music equipment and entertainment system. Plan to add more load soon.
I do not have any 240 volt yet but in next couple weeks will add another 8kwh battery which will give me a total of 16kwh @ 340ah and will add an additional Growatt inverter 48v in parallel with the one I already have. Then I will begin experimenting with split phase 240v. You can see in the last chart I posted I am carrying about 1000w of load max right now.
 

coolbz

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That’s cool, plenty of loads on your growatt. Mine does not come with WiFi dongle so I’ll try connect the USB port directly using a computer first.
 

iSwannie

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Here is today’s solar system with some explanation of what is going on. My goal is to reach 1000w continuous 24hrs a day.
 

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coolbz

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Here is today’s solar system with some explanation of what is going on. My goal is to reach 1000w continuous 24hrs a day.
So looks like you have around 200watt constant load, and maybe 100watt refrig, plus more in afternoon.
Did solar drop in afternoon due to cloud or shade?
 

iSwannie

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Yep carrying between 275 to 300 watt right now with all computer equipment, freezer and entertainment system. I added some more info to the graph explaining what is happening.
 

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Zwy

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It appears your system is working just fine. I'm currently in the process, cells arrived yesterday and will be moving to sourcing panels and ordering some 48V GW units for parallel operation.
 

coolbz

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Hi guys, in the past few days, I discovered an odd issue with my growatt 3000TL LMV-ES 48v system.

When I measured with kill-a-watt, my system shows around 33watt when there is no load, but when I measured with an AMP meter, it shows 1.6amp, which could mean 1.6*120 = 192watt. So I did a little more research, this situation means lower power factor (some power is sent back through neutral line and wasted). When I have solar power large enough to support load, the system still draws about 1.6amp from grid. By the way, I do not have battery in this system.

Have anyone seen this behavior in your system? Does this mean I'm charged for 192watt standby power usage by my grid power company even though I have no load drawing through grid beside this AIO inverter itself?
 
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