Growatt 12000T MPV not using PV for load

[BajaDave]

I have just finished setting up a system with:

14 455w panels in two strings
42kw LG NMC batteries in 6.5kw modules
Growatt 12000T MPV

I have param 1 set to SBU. So I should see the PV array being used for house load during the day, with batteries coming in only if load > available PV current.

What I see instead is the PV being used for house load and battery charging in the morning, and then when the batteries are topped off the PV array is no longer utilized and batteries are exclusively used to power house load.


Any ideas?
Acceptable input range for the MPP controller is 60–245 V.
PV voltages and currents:

 

[BajaDave]

In case anyone else runs into this with a Growatt inverter: After a lot of experimentation, I set float=bulk=56.6, and finally the growatt is using solar to feed the loads during the day.

 

[RCinFLA]

The Growatt LF models all run their SCC directly to battery terminals on inverter. They are like a PV system with SCC direct to battery DC coupling charging.

There is no current measurement differentiation between what comes from battery and what comes from SCC other than a battery terminal voltage rise as the result of SCC pushing current.

All PV to AC output power goes through LF inverter as if it came from battery, along with LF inverter efficiency loss. If battery needs charging it will likely get first priority on PV power. Only way it limits the PV power going to charging battery is to avoid raising DC input terminal voltage by PV power. This likely is based on battery state of charge being above a minimum level. 120Hz ripple current from AC inverter is filtered by battery to keep if off the PV panels which would reduce PV panel output.

The SCC PV to battery power conversion efficiency is not that good, about 90%, then there is the LF inverter DC input to AC output efficiency of about 93%, so net PV input to AC output is about 84%. The SCC is a synchronous buck switcher which is good but because the voltage ratio is so great between the PV input and battery voltage the switching duty cycle is low which hurts its efficiency. You will likely get a bit better SCC conversion efficiency by keeping PV input voltage to the low end of its range. This is opposite of their HF inverters which have better SCC efficiency with PV input voltage nearer to their high voltage range end.

 

[BajaDave]

Thanks for the information. Perhaps I’m missing something, but I’m not sure how your information explains why Growatt shut off the solar panels when float voltage was hit each day and switched to battery only mode?

After setting float to match bulk, the panels were finally engaged for the entire day, resulting in a full battery at the end of the day.

 

[mgoben64]

Having the exact same issue on my 6000, Dave and was tripping me out. How did you adjust the float?

 

[martym]

In case anyone else runs into this with a Growatt inverter: After a lot of experimentation, I set float=bulk=56.6, and finally the growatt is using solar to feed the loads during the day.

I could just hug you!! I'm way remote/off-grid and have spent three days trying everything I can think of. This "float=bulk=56.6" was the magic. Instantly I get 2+KW charging my lagging batteries. Any idea what the heck is going on here?

 

[mgoben64]

I could just hug you!! I'm way remote/off-grid and have spent three days trying everything I can think of. This "float=bulk=56.6" was the magic. Instantly I get 2+KW charging my lagging batteries. Any idea what the heck is going on here?

I have the EG4 48V server rack batteries. I take it the trick is to disable auto communication between Growatt and the batteries and manually configure them? Once you do that, the monitoring software will no longer track the batteries? I'm having the same issue but don't know to get the float=bulk command. Must be dense.

 

[martym]

I have the EG4 48V server rack batteries. I take it the trick is to disable auto communication between Growatt and the batteries and manually configure them? Once you do that, the monitoring software will no longer track the batteries? I'm having the same issue but don't know to get the float=bulk command. Must be dense.

The auto communication disables the manual/custom settings options. I have a 15 Kw DIY Li-ion pack with a JiKong active balancing BMS and haven't been able to establish auto communication. I have the SPF6000T DVM-MPT and the bulk/float manual settings are menu numbers 19 & 20. Battery type (setting 5) must first be set to "USE2" to make options 19, 20, and 21 available. Nothing magic about the 56.6V but the float=bulk seems to be the key. It is still quirky and non-intuitive but it mostly working. It baffles me that the manual could be this useless and support or other documentation non-existent. Inverter seems well made though...

 

[Rapptorr]

12k

 

[Zwy]

I could just hug you!! I'm way remote/off-grid and have spent three days trying everything I can think of. This "float=bulk=56.6" was the magic. Instantly I get 2+KW charging my lagging batteries. Any idea what the heck is going on here?

If you had looked in the archives here, you would have found the answer. I've been telling members for over a year to move float closer to bulk charge setting.

So, what is occurring? Basically, it works like this. The inverter runs off the DC bus, it doesn't know or care where that power comes from. It could be battery or it could be the SCC supplying the DC bus. Once the bulk setting has been hit, the SCC will terminate charging the DC bus until the float setting is hit. Pretty simple actually. Once the float setting is hit, the SCC will supply the DC bus, thus you see PV power being used to not only charge the battery but also can supply power to the inverter.

I prefer a float setting about 0.5V below the bulk setting. I set bulk up into the knee area on LFP and high enough the BMS will balance cells.

 

[WYtreasure]

Hey @BajaDave can you confirm your Growatt is the SPF 12000T DVM-MPV?

Interesting reading:

Growatt - Odd behavior

I know this is an old post, but I've experience the same issue with my new Growatt 3000w 24v. Battery topped off, solar turned off even though I was still pulling a decent load and the sun was out. Tonight I noticed my charge light was solid Green indicating full charge even though my SOC was...

diysolarforum.com

 

[WYtreasure]

-

 

[Rapptorr]

If you had looked in the archives here, you would have found the answer. I've been telling members for over a year to move float closer to bulk charge setting.

So, what is occurring? Basically, it works like this. The inverter runs off the DC bus, it doesn't know or care where that power comes from. It could be battery or it could be the SCC supplying the DC bus. Once the bulk setting has been hit, the SCC will terminate charging the DC bus until the float setting is hit. Pretty simple actually. Once the float setting is hit, the SCC will supply the DC bus, thus you see PV power being used to not only charge the battery but also can supply power to the inverter.

I prefer a float setting about 0.5V below the bulk setting. I set bulk up into the knee area on LFP and high enough the BMS will balance cells.

Thanks

 

[Darren67-72]

Jumping in, signature solar recommends....
Settings,
19- 58v
20- 56.5v
21- 46v
You can adjust from there, for your liking.

 

[Darren67-72]

Typo... setting 21- 46

 

[Rapptorr]

so do I just unplug the batt COMM cables? Thanks Tom

 

[Darren67-72]

Yes, use2. I left mine plugged in? At least, I would leave the daisy chain for batteries

 

[martym]

If you had looked in the archives here, you would have found the answer. I've been telling members for over a year to move float closer to bulk charge setting.

So, what is occurring? Basically, it works like this. The inverter runs off the DC bus, it doesn't know or care where that power comes from. It could be battery or it could be the SCC supplying the DC bus. Once the bulk setting has been hit, the SCC will terminate charging the DC bus until the float setting is hit. Pretty simple actually. Once the float setting is hit, the SCC will supply the DC bus, thus you see PV power being used to not only charge the battery but also can supply power to the inverter.

I prefer a float setting about 0.5V below the bulk setting. I set bulk up into the knee area on LFP and high enough the BMS will balance cells.

I have a good, practical understanding of electricity (25 years as a corrosion engineer). The solar stuff has been self taught and just now getting to the practical hands on part - so yes, newbie. If I understand you correctly: the battery SOC alone turns the PV on & off; the inverter load may coincidentally pull from the DC bus when SCC is charging but inverter load will not engage the SCC. Correct?
Also you refer to the LFP knee area - what vdc range is that? I did look in the archives (a lot) and didn't ask the right questions apparently. Thanks for your help

 

[Rapptorr]

Thanks

 

[Zwy]

I have a good, practical understanding of electricity (25 years as a corrosion engineer). The solar stuff has been self taught and just now getting to the practical hands on part - so yes, newbie. If I understand you correctly: the battery SOC alone turns the PV on & off; the inverter load may coincidentally pull from the DC bus when SCC is charging but inverter load will not engage the SCC. Correct?

That is correct, the inverter just pulls off the DC bus and does not interact with the SCC to control charging. SCC only looks at your battery voltage and you set it where you want it to end bulk and begin float. Float is basically maintaining SOC at current level if PV is available. If PV isn't available, then it draws the power completely from the battery.

Also you refer to the LFP knee area - what vdc range is that? I did look in the archives (a lot) and didn't ask the right questions apparently. Thanks for your help

3.45V to 3.5V per cell. For 12V system, 13.8V to 14.0V. For 24V, 27.5 to 28.0. For 48V, 55V to 58V.

My BMS balancing doesn't kick in until 3.4V. At 3.45V to 3.5V, it allows balancing to occur.