Growatt - Odd behavior

apctjb

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When the Growatt resumes, does it just maintain float, or does it re-bulk?
It resumes in Bulk and starts the charge cycle fresh. I wonder if the "logic" behind this is once float is reached, and loads are below X, then better to turn off the MPPT charging to reduce tare loss (the MPPT charger adds to tare losses). With 200AH of lead acid batteries 1.5V drop is going to happen fast once a load is applied so charging resumes. Not so quick with a 32kwH LiFePO4 battery bank.
 

snoobler

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Good to know they at least practice the re-bulk method that everyone else does. I'm not aware of any other system that addresses tare loss (speaking like I know what you're talking about). Other systems continue float until they can't maintain it after sundown.
 

apctjb

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Tare Loss. Definition: Loss caused by a charge controller. One minus tare loss, expressed as a percentage, is equal to the controller efficiency.

🙂 Tare Loss. Definition: Loss caused by a charge controller. One minus tare loss, expressed as a percentage, is equal to the controller efficiency.

At some point keeping MPPT charger on consumes more energy than it is adding to the battery. Not saying Growatt engineers had this in mind ( if so it needs some serious tweaking ), just wondering out loud...
 

snoobler

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🙂 Tare Loss. Definition: Loss caused by a charge controller. One minus tare loss, expressed as a percentage, is equal to the controller efficiency.

At some point keeping MPPT charger on consumes more energy than it is adding to the battery. Not saying Growatt engineers had this in mind ( if so it needs some serious tweaking ), just wondering out loud...

Ah. Thanks.

Given that the AiOs pull many watts at all times even with no loads, I assert that tare loss can never happen when meaningful solar energy is available. The units I helped configure idled at 100W draw in parallel. I can't see tare loss ever being a factor when there's a minimum 100W load at all times. No way the tare loss will ever be above 100W.
 

apctjb

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. I can't see tare loss ever being a factor when there's a minimum 100W load at all times

Agree totally.

In theory if you turn off the MPPT portion of an all in one and the 100W standby loss you mention may drop to 50W. The MPPT charger in an all in one has an efficiency similar (90%) to that of the inverter portion (90%), and the total standby loss of in all in one is the sum of the loss of individual parts built into one box.
 

Cheap 4-life

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Completely different setup but I use an outback fm80 chargecontroller to charge my lithium batteries. To allow the charge controller to float (continue to supply) the loads once the battery is full, I have to set chargecontrollers float voltage at a slightly lower voltage (.2v) than absorption. This stops the charge controller from thinking the battery is completely full even though it is full. If I didn’t do this the charge controller would stop floating and then loads would only use battery
 

snoobler

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Agree totally.

In theory if you turn off the MPPT portion of an all in one and the 100W standby loss you mention may drop to 50W. The MPPT charger in an all in one has an efficiency similar (90%) to that of the inverter portion (90%), and the total standby loss of in all in one is the sum of the loss of individual parts built into one box.

Yikes. Thanks. Didn't know about the 90% efficiency of the MPPT. That may explain something for the setup I mentioned.


Completely different setup but I use an outback fm80 chargecontroller to charge my lithium batteries. To allow the charge controller to float (continue to supply) the loads once the battery is full, I have to set chargecontrollers float voltage at a slightly lower voltage (.2v) than absorption. This stops the charge controller from thinking the battery is completely full even though it is full. If I didn’t do this the charge controller would stop floating and then loads would only use battery

I don't understand that. My neighbor has two FM80, and it drops to a normal float and continues to power the loads with solar.

If you experience the unit saying "CHARGED" and it refuses to provide solar, it's malfunctioning. My neighbor has experienced this a few times in the last year, and there are threads about it on other forums and one on this one.
 

Cheap 4-life

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Yikes. Thanks. Didn't know about the 90% efficiency of the MPPT. That may explain something for the setup I mentioned.




I don't understand that. My neighbor has two FM80, and it drops to a normal float and continues to power the loads with solar.

If you experience the unit saying "CHARGED" and it refuses to provide solar, it's malfunctioning. My neighbor has experienced this a few times in the last year, and there are threads about it on other forums and one on this one.
I’ve owned 3 outback chargecontrollers. 2 fm60s and 1 fm80. Each one would say charged if the float voltage was set above the absorption if the loads were low at that time
 
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Cheap 4-life

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Yikes. Thanks. Didn't know about the 90% efficiency of the MPPT. That may explain something for the setup I mentioned.




I don't understand that. My neighbor has two FM80, and it drops to a normal float and continues to power the loads with solar.

If you experience the unit saying "CHARGED" and it refuses to provide solar, it's malfunctioning. My neighbor has experienced this a few times in the last year, and there are threads about it on other forums and one on this one.
When I originally had the “charged” problem I researched it on this forum and outbacks forum. That’s where I read to set the absorption slightly above float when charging lithium. It works wonderfully
 

apctjb

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That’s where I read to set the absorption slightly above float when charging lithium. It works wonderfully

Thanks, will give it a try!
 

debron55

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just wanted to update folks.
Curious; are your batteries Lead Acid or LiFePO4. Just looking for useful data points. Thx
LifePO4 CALB 100ah cells configured in a 24volt configuration with OverKill Solar BMS.
 

debron55

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just wanted to post an update. I'm not declaring victory yet but Snoobler and Lt. Dan's posting of their settings were incredibly useful. I changed my unit setting 5 from USE2 to USE and (granted with only 1 day of observations under my belt) the unit appears to be behaving in a manner more consistent with my expectations. I really can't thank folks enough to taking the time to share their info and just the overall community of folks kicking in ideas and their own observations. I am not sure what the difference in USE vs USE2 actually is but it seems to lock bulk and float. It may do other things as well... in addition to the use setting I also was then able to adjust bulk and float so that there was some voltage difference between the two. In USE2 it appears the float voltage is completely locked to the Bulk voltage. IE I could not change the float voltage. well I could change it. save it and when I would navigate away and back or look at it on pvkeeper2 it would be set back to 19 (bulk) setting.
 
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apctjb

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1622237976722.png

I found the efficiency for the Growatt MPPT charger; higher than I had estimated....
 

apctjb

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Manual says 90-92% which what I have measured with moderate load.
 

SiliconOrb

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This thread caught my eye because I saw the same initial behavior on my system.

I'll preface this by asking for forgiveness in advance, as I am new to solar, but not new to electronics. My take on the Growatt all-in-on system is that, from a philosophical standpoint, the main power source in the system is the battery bank. The reason I say this is because the Growatt won't even turn on without it, and it never seems to be idle. It is either being charged or discharging, and the job of the solar is to maintain the battery bank, thus the Growatt itself, and then power other loads with whatever is left over.

When the loads are small and/or inconsistent, the system starts having to make decisions on which parts of itself to use in order to minimize losses and keep efficiency at the highest levels possible. So it may be that, the given load on the system, the rate at which the batteries discharge, etc..., cause the Growatt to decide that the losses from powering up the voltage converter for solar when the batteries are at near or full charge, are an unnecessary expenditure. This may be especially true when there is abundant solar energy available, so it "knows" that whatever power it pulls from the batteries can be recovered quickly when the batteries reach a lower-than-full SOC. So it takes the route of highest efficiency, and turns off the solar converter, until it's use is necessary.

Now to the problem. The Growatt doesn't have a LifePo4 battery setting, so it isn't really aware of the battery bank characteristics. If your loads aren't high enough to tax the batteries, it may take it longer to decide that it's time bring in the solar. The solution in my case, was to simply increase the size and frequency of the load. The moment I connected a refrigerator (and now, a small freezer) this issue seemed to disappear. I suppose one could fiddle with the numbers to minimize this behavior, but doing so at the possible expense of total capacity might be somewhat counter-productive. Perhaps the addition of a useful, constant load, and maybe a timer so it only kicks on during daylight hours would be enough to sort it out.

My solution was to tax the system and let it do it's thing. But if the system never returns to solar and leaves you with half-discharged batteries at the end of the production bearing day, then there are likely other issues at play.
 
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debron55

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This thread caught my eye because I saw the same initial behavior on my system.

I'll preface this by asking for forgiveness in advance, as I am new to solar, but not new to electronics. My take on the Growatt all-in-on system is that, from a philosophical standpoint, the main power source in the system is the battery bank. The reason I say this is because the Growatt won't even turn on without it, and it never seems to be idle. It is either being charged or discharging, and the job of the solar is to maintain the battery bank, thus the Growatt itself, and then power other loads with whatever is left over.

When the loads are small and/or inconsistent, the system starts having to make decisions on which parts of itself to use in order to minimize losses and keep efficiency at the highest levels possible. So it may be that, the given load on the system, the rate at which the batteries discharge, etc..., cause the Growatt to decide that the losses from powering up the voltage converter for solar when the batteries are at near or full charge, are an unnecessary expenditure. This may be especially true when there is abundant solar energy available, so it "knows" that whatever power it pulls from the batteries can be recovered quickly when the batteries reach a lower-than-full SOC. So it takes the route of highest efficiency, and turns off the solar converter, until it's use is necessary.

Now to the problem. The Growatt doesn't have a LifePo4 battery setting, so it isn't really aware of the battery bank characteristics. If your loads aren't high enough to tax the batteries, it may take it longer to decide that it's time bring in the solar. The solution in my case, was to simply increase the size and frequency of the load. The moment I connected a refrigerator (and now, a small freezer) this issue seemed to disappear. I suppose one could fiddle with the numbers to minimize this behavior, but doing so at the possible expense of total capacity might be somewhat counter-productive. Perhaps the addition of a useful, constant load, and maybe a timer so it only kicks on during daylight hours would be enough to sort it out.

My solution was to tax the system and let it do it's thing. But if the system never returns to solar and leaves you with half-discharged batteries at the end of the production bearing day, then there are likely other issues at play.
thanks for the info and ideas. I do believe I have figured out what the issue was. Through looking over a few others settings I noticed everyone that was working had used USER as the battery type ( also called USE). There is a new setting added in a recent firmware called USE2. ANd allegedly this was the preferred for LifePo4. FOr me at least this did not prove to be the case. For me USE2 would not allow any difference between Bulk and float. And there may be other things that USE2 does that were not as discoverable. THere is basically no documentation that I could discover for this setting. Without the unit being able to go to a float different than bulk the unit was alwas set to float at the same voltage. When this would happen the system would essentially say (or at least it seemed to me) ... I have hit bulk and would like to settle down to float and get into a balance with the overall consumption . But for some reason it did not process that sort of balance level as being attainable so it would simply say ok ... I've hit my voltage shut off the solar panels. The system would shut off the panels until the batteries were drained to their switch to utility level . This could take hours. I had tried heavier loads - I mean 25% was to me a reasonable load that would show me something.. and it had no effect. Going to USE setting for battery type hit the mark perfectly and the unit is behaving as hoped.

Growatt_EnergyTrend_2021_05_27.jpg
 
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