diy solar

diy solar

Growatt SPF 12000t architecture Question

tweekzilla

New Member
Joined
Jun 23, 2021
Messages
34
First post!

I'm thinking of moving most (not all) of my main-panel circuits (including a fairly low power A/C unit) onto an off-grid panel that is powered by a growatt 12000T. The main reason for this is TOU load shifting (our afternoon rates in socal are 60c/kwh and going up). I do currently have a grid-tie solar system which I will leave in place. The plan is to charge the batteries at night (cheap electricity) from the grid via the inverter and when the price of electricity gets expensive switch over from grid-power to battery+solar on the subpanel. If I run out of power (battery/solar) then the inverter would switch back to grid via the transfer switch. Whilst the load is shifted the grid-tie solar will be racking up TOU credit that I can put towards cost of electricity at night (and electric car charging).

A) does this make sense?
B) Does the growatt 12000T have any kind of ToU settings - i.e. priority Grid between 10pm and 8am then priority solar->battery->grid between 8am and 10pm? If not is there an API so could program it via a raspberry Pi?
C) Any gotcha's with this idea? i.e. you loose power for a brief second when the transfer switch kicks in for example?
 
A. Yes
B. No TOU settings. Most projects appear to only get information from the inverter, but if you search for modbus growatt you'll find a few documents that might give you enough to get started. You'd want to set the AC charging current to control whether it's charging or not.
C. The Growatts are very good at transfer time - you'll notice when the lights flicker, but it's not long enough for most electronics to reset.
 
No out of the box TOU modes as stienman said. There are a couple of undocumented settings in the mobile app that might get you closer (see graphic below). *BUT* I can’t recommend buying this unit for this purpose until someone else that has successfully used it chimes in with their experience. This setting is likely aspirational and could have unintended consequences.

As for gotchas, I would be concerned about the method used with switch over from the 12000t *off grid inverter* to your current grid-tie solar system (see: frequency Synchronization). Also I would want to confirm how backfeed during grid outage would be prevented in this configuration.

Might be better to consider adding an AC coupled battery system to your existing grid-tie system if that is an option for you.
 

Attachments

  • D8402424-134C-47E9-BDB8-043180470B86.jpeg
    D8402424-134C-47E9-BDB8-043180470B86.jpeg
    167.8 KB · Views: 16
No out of the box TOU modes as stienman said. There are a couple of undocumented settings in the mobile app that might get you closer (see graphic below). *BUT* I can’t recommend buying this unit for this purpose until someone else that has successfully used it chimes in with their experience. This setting is likely aspirational and could have unintended consequences.

As for gotchas, I would be concerned about the method used with switch over from the 12000t *off grid inverter* to your current grid-tie solar system (see: frequency Synchronization). Also I would want to confirm how backfeed during grid outage would be prevented in this configuration.

Might be better to consider adding an AC coupled battery system to your existing grid-tie system if that is an option for you.
Thanks for you response - I *think* I can change the settings via modbus over RS-422 but I need to do a bit more research.

I don't believe there will be any backfeed issues as I'll move over sub-circuits to a separate panel that would never see the "Grid" except maybe a GND tie. The only grid connection would be the GRID->Inverter that is used as a bypass when the battery/solar is too low or for charging the batteries.
 
tweekzilla, are you able to get tou function working with Growatt. I am also interested in this functionality.
 
I tried the settings with charge time start and charge time end and they do not do anything on the SPF 12000T DVM inverter. I would be interested in a schedule setting to charge batteries at night from utility when the rate is cheaper but I am unable to do it. tried with both shine phone app and the wifi dongle. or via USB with a laptop and the PV Keeper software and neither will allow a schedule to be set.
Anyone would have a better idea on how to implement a scheduling option with this inverter? Either via third party software, or any other way.?
 
Back
Top