My inverter is home Growatt 6KW SPF 6000T DVM INVERTER/CHARGER Off-Grid yeah!

[floydR]

Was going to chew UPS out but the lady working the counter looked like she had heard all the bitches about UPS so wasn't worth it. Now to build the 14s battery it.
Later floyd

 

[DG98]

Congrats! I believe that's the same unit I am using in my off-grid barn building, connected to a homemade 14s14p battery made from Leaf modules. It took me a while tinkering around with it as my first project, but it's been running great for 2-3 months now.

Cheers, John

 

[floydR]

Cool How hard was it to configure for your leaf wall?
The inverter is the biggest purchase of my project and maybe it will make me finish the project. It is sitting against a desk right now.

Later floyd

 

[DG98]

Floyd -- it wasn't too bad, but the documentation is pretty poor. Physically building the battery wasn't hard, of course -- I made seven stacks of fourteen Leaf modules per stack (each module is already 2s), and installed them in an old computer server rack that I had in the shop. I made my own bus bars out of aluminum bar stock, and re-used the Leaf bolts to connect the bus bars to the battery modules. (I disassembled two full Leaf packs that were pulled directly from cars, so I had all the hardware. I even repurposed some of the OEM wiring for my BMS leads.)

I will admit that I had a hard time getting the voltages configured in the Growatt to charge the battery properly. There are two options that will work for my configuration -- one pre-set for Lithium Ion, and the other for "custom configuration" or something like that. I believe I wound up using the latter, which allows you to set the charge voltages and so forth manually. One thing that I discovered (which wasn't in the documentation, that I saw) is that each time I made a change to those settings, I had to "reboot" (power cycle) the inverter to make my changes take effect. Before I figured this out, I was having a huge amount of frustration -- on a full-sun day, I was adjusting charge voltages and yet I was getting no charge to the pack, etc. Once I figured out that I had to reboot the inverter to see the effect of my changes, I had a lot more success in getting the thing configured and working.

I don't have all of this in front of me, but as I said, I think I wound up using the custom config settings. At peak, I charge my pack to 57.2v, or a little under 4.1v per cell. That's just for longevity, since I don't need every single ounce of possible energy in the pack. I can't remember off-hand where I have my cutoff voltage set, but I haven't gotten close to it since the system went up. I keep a spreadsheet of daily activity (which comes from the BMS, more on that below), and it looks like on average my pack cycles between 53.7v and 56.4v. On average I am using about 4kwh of energy per day in that building. (I don't trust the SOC data from the BMS, honestly. It thinks the pack is running between 52% and 79%, but I just don't have any faith in the accuracy of those numbers.)

For reference, I have 18x 340w panels mounted on the south-facing roof of the barn, feeding into the Growatt inverter-charger. I actually have a second Growatt charge controller, but it turns out I haven't installed it because I haven't needed more panels to keep the pack charged. A handful of times, during multi-day periods of rain and heavy clouds (and in one extremely rare instance two or three weeks ago, five consecutive days with a foot of snow covering my panels...in Texas, no less), I have connected my small 8kw gas generator to the Growatt and run it for an hour or two to get some charge in the pack.

FYI, I am using a Batrium BMS system on the homemade Leaf pack -- but let me be the first to admit that I am not using it very effectively. Batrium is not compatible with the Growatt system, at least as far as CANBUS communication, etc., so my BMS cannot control the Growatt. In reality, it means that my BMS is basically sitting there being a very expensive cell equalizer/balancer. The Growatt configuration itself is what controls the charge levels, voltages, and so on. To be fair, though, I do still have the safety triggers in the Batrium set up -- for example, I have a shunt trip on the main breaker where if things get too far out of whack, the Batrium can trip the breaker and physically disconnect the battery from the rest of the system. That's the last line of defense, I suppose. My favorite feature of the Batrium is that it is WiFi-connected, so I can be at the house (a half-mile from the barn) and check on battery capacity without having to get out in the weather, etc.

My next project is a much larger (100-150 panel) grid-tied array on the main house. I'd like to do a battery backup on that as well, but I've got another thread about how my grid-tie inverters are set up for high-voltage packs, etc. I don't want to sort all that out on my own, so I'm looking at perhaps adding an AC-coupled battery solution, and cobbling up a way to disconnect from the grid and still be able to use my solar array by "faking the grid" from the battery system. All that is still in the infancy stages of planning, except for the pallets of panels stacked behind the barn...

Hope that info helps, or at least gives you a little motivation about the excitement ahead. It really is fun the first time you go live and run something from the system. Please post as you work on your system. I'm not here often, but I'll check in when I get a notification. Will be interested to follow your updates.

Cheers, John

 

[floydR]

Thanks for the reply. yes The hardcopy docs I got with the inverter are mighty thin. I haven't really looked at the pdf to much as of yet. need to clean up the garage But I do have a corner wall picked out to hang the inverter and next to the inverter will be my LiFePO4 set up. the info you have given me will help.
Thank You
Later
floyd

 

[DG98]

I just had one other thought. I said above that I am using an average of 4kwh per day in that building. I've decided that is probably inaccurate. That data comes from the BMS, which is measuring across the shunt. So that means I am using 4kwh/day out of the battery pack. I believe that the Growatt is configured to power loads from the panels first, and then pull current from the pack if needed (or push excess current from the panels into the pack during charging). The way I am wired up, the BMS isn't seeing power which goes straight from panels to inverter to loads -- it sees only power in and out of the pack.

Certain loads (like a 9k-btu mini-split) run 24x7. I'd say that for at least 4-6 hours per typical day, that load is handled completely by the panels and inverter without battery interaction. It's an inverter-style heat pump, which draws between 500-1000w depending on the ambient temp and where I set the thermostat -- it seems to be very efficient, and it has certainly been effective at controlling the temp in a small (~300 ft^2) buildout within the barn. Similarly, I have a standard 40-gallon water heater on a timer, which lets it run two hours per day during "peak sun." The water heater draws as much as 3000w when the timer powers it on. (I had to pull the original elements out and put in lower-wattage elements -- the originals would have overloaded the 6kw inverter, and I don't need fast recovery on that tank.) On a full-sun day, this can be mostly or even entirely powered by the panels. On a cloudy day, of course, this is a substantial pull on the battery.

Anyway, all that to say that my prior post about average use could have been misleading. I'm using 4kwh/day out of the battery pack, presumably mostly during the overnight hours. I'm now finding myself very curious how much power I'm actually using overall. I might have to look at my clamp multimeter and see if it can log a day or two, and measure the feed between the inverter and the main breaker panel just to get some "real use" numbers.

Cheers, John

 

[Cheap 4-life]

Hey Floyd, I read somewhere that growatts new inverter charger can supply power to loads from pv panels without using the battery.
Wondering if it can operate like a grid tie inverter, letting the utility-grid supply the power loads need that is more than the max output of the inverter? And the inverter continues to supply its max out-put

 

[floydR]

I will find out I haven't really read the manual but it does seem to have a mode SBU not real clear on if that means it will still supply power from the SB and the Utility at the same time, It would probably revert to the utility only mode when the max is exceeded. Good question

Later floyd

 

[DG98]

I believe it does have a mode where it will power loads with utility power first, then use panels and battery. However, it is not at all "grid tie" because it will not export power to the grid. If my recollection is correct, there is a max amperage that it will draw from the utility input. (I'm certain there's as max amperage it will draw from the utility input to charge the pack. I forget, but I want to say it's 30A.) Likewise, I think there is a mode that uses the grid input as a "boost" when the inverter is otherwise maxed out -- but I'm not sure.

In my case, where it is truly off-grid, I have leads for a gas generator connected to the utility input. One oddity is how the Growatt behaves when the generator is on. It's a pure sinewave inverter, and my generator is a pure sinewave output. Yet when the generator is running to charge the pack, the loads behave like they are connected to a modified sinewave inverter -- lights flicker, etc. I can't explain it, but it's decidedly annoying.

Cheers, John

 

[Cheap 4-life]

I believe it does have a mode where it will power loads with utility power first, then use panels and battery. However, it is not at all "grid tie" because it will not export power to the grid. If my recollection is correct, there is a max amperage that it will draw from the utility input. (I'm certain there's as max amperage it will draw from the utility input to charge the pack. I forget, but I want to say it's 30A.) Likewise, I think there is a mode that uses the grid input as a "boost" when the inverter is otherwise maxed out -- but I'm not sure.

In my case, where it is truly off-grid, I have leads for a gas generator connected to the utility input. One oddity is how the Growatt behaves when the generator is on. It's a pure sinewave inverter, and my generator is a pure sinewave output. Yet when the generator is running to charge the pack, the loads behave like they are connected to a modified sinewave inverter -- lights flicker, etc. I can't explain it, but it's decidedly annoying.

Cheers, John

Nowadays it seems to me that grid tie no longer exactly means export to the grid. Electric companies started acting like they are being cheated and saying self generated power users are not paying their fair share. They started giving less credit for over generated power and started charging higher fees etc. In some areas its even worse. Also IMO it’s always been better to save excess power generated into a battery to use yourself rather than give it to the electric company for peanuts.
There is a few grid tie inverters out there that limit the production to only what the loads actually are. And allow excess power to be saved in a low voltage battery. They do this with CT clamps on the homes mains wires. Solark, outback, Sofar Deye and SunG are the only ones that I found with this capability. The inverters will continue to supply full power when there’s surges (or constant load) above its max output (letting the utility supply the excess needed) like a grid tie inverter setup. They still allow for low voltage battery storage for excess pv power when there is more solar than loads are using like an offgrid inverter setup.

 

[Roland W]

Nowadays it seems to me that grid tie no longer exactly means export to the grid. Electric companies started acting like they are being cheated and saying self generated power users are not paying their fair share. They started giving less credit for over generated power and started charging higher fees etc. In some areas its even worse. Also IMO it’s always been better to save excess power generated into a battery to use yourself rather than give it to the electric company for peanuts.
There is a few grid tie inverters out there that limit the production to only what the loads actually are. And allow excess power to be saved in a low voltage battery. They do this with CT clamps on the homes mains wires. Solark, outback, and SunG are the only ones that I found with this capability. The inverters will continue to supply full power when there’s surges (or constant load) above its max output (letting the utility supply the excess needed) like a grid tie inverter setup. They still allow for low voltage battery storage for excess pv power when there is more solar than loads are using like an offgrid inverter setup.

Exactly, if you have a grid connection, then AC-coupled systems, as you are describing here are the future. You want the grid as a helper from a physical, but do not need it from a financial standpoint.

 

[Cheap 4-life]

Exactly, if you have a grid connection, then AC-coupled systems, as you are describing here are the future. You want the grid as a helper from a physical, but do not need it from a financial standpoint.

I’m not specifically referring to AC coupled systems. For example, my system uses a dc charge controller that goes to dc the batteries, which power the grid tie inverters that uses current transducers. I keep the utilities power (grid) for start up surges and occasional high loads. Besides that my electric bill is next to nothing. This way I don’t have to be so hard on the batteries. I saved a good chunk of change from not sizing the inverters and batteries for the surges and occasional high loads.

 

[Cheap 4-life]

Sorry Floyd, I seem to somehow be good at high jacking posts

 

[floydR]

No problem I feel good about starting something that people will comment on. besides my inverters aren't doing anything right now.
Later floyd