Growatt - Odd behavior

debron55

New Member
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.)
Sorry I have been absent so long - DataCenter duties were extreme this last month - I did send them exactly that question RE: can they provide documentation regarding the comm protocol. Will let the group know their response.
 

debron55

New Member
Sorry I have been absent so long - DataCenter duties were extreme this last month - I did send them exactly that question RE: can they provide documentation regarding the comm protocol. Will let the group know their response.
SO - crazy as it may seem they provided the communication protocol documents.
 

Attachments

  • 1xSxxP_ESS_protocal_rev _23_20171128 SPF5k MHP5k.pdf
    255.5 KB · Views: 14
  • Growatt BMS CAN-Bus-protocol-low-voltage-V1.08.pdf
    663.3 KB · Views: 12

fazeshift

Solar Enthusiast
Sorry I have been absent so long - DataCenter duties were extreme this last month - I did send them exactly that question RE: can they provide documentation regarding the comm protocol. Will let the group know their response.
SO - crazy as it may seem they provided the communication protocol documents.

No need to apologize. (I have past experience with the demands of the IT field too)

Wow, that's awesome they did provide some protocol documentation. I skimmed through - looks useful. I'm going to play around translating the non-English parts, and see if this idea is feasible.
 

fazeshift

Solar Enthusiast
Translated docs attached, if anyone else is curious. Please excuse the table formatting that got trashed in one - looks like most of that was already English.

There is a lot to digest. I should probably create a new thread, as to not derail the existing discussion here.
 

Attachments

  • Translated copy of 1xSxxP_ESS_protocal_rev _23_20171128 SPF5k MHP5k.pdf
    188.6 KB · Views: 13
  • Translated copy of Growatt BMS CAN-Bus-protocol-low-voltage-V1.08.pdf
    196.2 KB · Views: 8

solarstuff

Solar Enthusiast
Just helped someone configure two of these in parallel 120/240V operation, and he experienced something similar.

Prior to final configuration, the unit behaved as the OP described. After reconfiguration and the complete hard "reboot" necessitated by wiring changes that completely disconnected the units from all sources, proper operation has initiated:

Bulk to bulk
Hang out there awhile.
Drop to float.
Hold float and power loads with solar.

IMHO float should not be above 27.2 as floating them above 3.4V/cell is never recommended and can damage cells.

View attachment 50656
View attachment 50657
View attachment 50658
Are these numbers safe for AGM? The red numbers, in a 24v system?
 

coolbz

New Member
HELP! I'm getting BMS cell over-voltage warning almost everyday.

I'm running SBU mode with US2, CV and float volt both at 55v per Ian suggestion. Everyday solar support load as first priority and charge battery when it has surplus power during the day. Once battery is charged to CV, Growatt does stop charge and then battery volt drops between 53-54v, but then Growatt started to charge battery again toward CV volt. This repeat several times in afternoon. Then two battery cells start to drift higher until one trips BMS to shut off charge. Afterawhile, that cell's volt drop to the point so BMS recovers. This is not normal. Did I do something wrong or Growatt or battery having issues?
 

Lt.Dan

Photon Sorcerer
If the battery is out of balance, its not an inverters fault. Look into why the battery is going out of balance. Need a top balance? One cell bad?
 

coolbz

New Member
If the battery is out of balance, its not an inverters fault. Look into why the battery is going out of balance. Need a top balance? One cell bad?
I believe there are at least two issues.

The main issue apparently is one battery cell not perfectly balanced, or it has lower capacity so it's voltage shot up and down near the high and low charge state. I bought battery from batteryhookup and the shipping padding was missing at side and bottom of packages, most of all padding was on the top of box, which could easily cause damage if the box was dropped from a feet above ground. If one or few cylinders out of 20 loose connection from solder, it will definitely cause lower capacity and never able to achieve both top and bottom balance.

The second issue is still around Growatt inverter, which seem to keep trying to charge battery during the day as long as battery voltage is lower than CV.
 

Zwy

Solar Addict
I believe there are at least two issues.

The main issue apparently is one battery cell not perfectly balanced, or it has lower capacity so it's voltage shot up and down near the high and low charge state. I bought battery from batteryhookup and the shipping padding was missing at side and bottom of packages, most of all padding was on the top of box, which could easily cause damage if the box was dropped from a feet above ground. If one or few cylinders out of 20 loose connection from solder, it will definitely cause lower capacity and never able to achieve both top and bottom balance.

The second issue is still around Growatt inverter, which seem to keep trying to charge battery during the day as long as battery voltage is lower than CV.
Lower the float to 0.5V less than bulk. I'd also consider lowering bulk charge 0.5V and see if the cell continues to be a runner that trips the BMS.

Most here use USE and not USE 2.

And yes, top balance might be required.
 

coolbz

New Member
Lower the float to 0.5V less than bulk. I'd also consider lowering bulk charge 0.5V and see if the cell continues to be a runner that trips the BMS.

Most here use USE and not USE 2.

And yes, top balance might be required.
Thanks for all advises! I have done all of these and it is very helpful. The only issue remaining seem to be one or two battery cells have smaller capacity so they tend to go up and down earlier than others if I use aggressive parameters (higher bulk charge and lower discharge). For now, I'm not worry too much and am using conservative parameters.

My next project would be crypto mining and going to check Will's new videos. May the sun god shine forever!
 
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