AC Charging From excess solar

integlikewhoa

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Hello,

I'm in California USA.I have installed my own 40 panel,14.8kW Enphase Micro Inverter system in the last year which is permitted and backfeeds excess solar to the grid. I then buy back at night and when my loads exceed my production. I pay high rates during peak hours of the day up to 8pm andI have now decided to DIY a battery to help mostly peak shave. Power hardly ever goes out in my area (been few years and even then it was out for a few hours). I wouldn't mind and will probley plan to have some off grid manual transfer at some point but for now I would like to get some GTIL's maybe 4-8kW worth to cover my AC/hot water heaterand otherloads during the after noon hours. I ordered(2,900)20kWH of 18650s to get started on a 14s200p setup. Batrium management also in the works.

So my question or problem is charging the batteries. I want to charge them from excess solar which usually in the early hours of the day (I'm at work not charging the EV cars yet). But I don't want to pull from the grid I want to try and increase and decrease charginging amps based on excess solar production. I do something similar now with charging the EV's. The charger output to the vehicle checks with Enphase controller every min on how much is being pushed back to the grid and raises lowers or starts and stops charging.

Does anything like this exist? I was looking in to something like the Eltek Flatpack2 controlled via can by the batrium but that doesn't seem to offer what I need. Also don't like the Flatpack is not dual Phase USA current but maybe two will fix that.

I'm also trying to install all this in the garage (or behind it)on a 100amp subpanel well away from the Main panel.

Whats my options?

Thanks,
 

Cheap 4-life

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Having the GTIL2s constantly use power only from the battery will drastically reduce how many years your battery will last. This is apposed to the GTIL2s using the power directly from charge controller when its available instead of the battery. I guess you dont have much choice since your dc is converted to Ac at the micros.
 

integlikewhoa

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Cheap4-life said:
Having the GTIL2s constantly use power only from the battery will drastically reduce how many years your battery will last. This is apposed to the GTIL2s using the power directly from charge controller when its available instead of the battery. I guess you dont have much choice since your dc is converted to Ac at the micros.
I'm not sure what you mean.....I think its the same.

GTIL2's will only be used when load is more then what solar is producing. AC microinverters cover the AC load and more when the sun is producing so the GTIL's wont do anything but sit and idle. As the sun goes down and there is still AC demand in the house thenthe GTIL2's with a limiter will see power is being pulled from grid and then start to pull from battery and supplement the AC micro inverters and will work through the night to supply power from batteries only running a small load.
 

Cheap 4-life

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You right, basically the same. Your micros are doing basically the same thing as feeding power directly from chargecontroller to GTIL2 would do. My mistake.

As for your question. Whenever you are selling back to the grid you could instead charge the battery. Maybe you could use a micro controller to trigger a relay to start Ac charger-charging when theres power (more than your loads are using) being fed into the grid. Daromer did a video for a dump load and a microcontroller that triggered a relay. Might be helpful.
 

integlikewhoa

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Cheap4-life said:
You right, basically the same. Your micros are doing basically the same thing as feeding power directly from chargecontroller to GTIL2 would do. My mistake.

As for your question. Whenever you are selling back to the grid you could instead charge the battery. Maybe you could use a micro controller to trigger a relay to start Ac charger-charging when theres power (more than your loads are using) being fed into the grid Daromer did a video for a dump load and a microcontroller that triggered a relay. Might be helpful.
I'm pretty sure I could trigger a relay for on/off control fairly easy but I was hoping to get more of an amperage control instead if possible. Kind of like the GTIL2 does. it auto ramps up and down based on load it sees coming from the grid to zero out usuage.

I was hoping to to do the reverse for charging the batteries. As amps start flowing out to the grid the charger ramps up until it zeros out or hits max charging to the batteries.

I'm not sure this is possible but looking for ideas.

Thanks,
 

not2bme

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You need an AC Coupled solution. So you're charging through the AC and then discharging back into the grid at night. So you need some sort of hybrid system. The one thing you'd need is a current sensor at the mains so you know if you're selling to the grid. Once you have that you can then enable charging of your batteries when you detect you are selling, then at night you will try to use the battery to generate the power you detect you are consuming.

Now I have a schneider XW 6848 and there's a user on this forum that's trying to just ac couple based on charging during the day and selling at night when it's more expensive. But he's having issues with it because the settings conflict on when it should charge and when it should sell. My system is about to go online soon but I can tell you the schneider product is a slight mess. The configuration is quite convoluted. On top of it Schneider requires you to buy a gateway box just to communicate with the inverter, and it costs $700 alone. Quite a ripoff. But I've been communicating with it via modbus and I know I can get it to do what you need it to do.

But during my research, I noticed Outback offers a product called SkyBox. It's an all in one solution that has all the current sensing built in, and all the software built in. You might want to research in this box to see if it might do what you want it to do.

Otherwise if on a budget, I'd consider a MPPsolar hybrid unit, use the SDM630 meter and probably needs some python script written so you can control it.
 

integlikewhoa

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So I have looked into some Hybird units but I got lost in all the rewiring and such. I'm in the US and have dual phase 240v (120v+120v). MPP solar doesn't have many dual phase options, and the one true one is a 24v battery option unless i missed something. Using their Offgrid dual phase to charge the batteries then maybe during an outage I could manually rewire and back feed for emergency use is an option I have kicked around. But the 1k price tag, lack of real batrium control had me leaning towards the Flatpack2's which I could get used fairly cheap.

Also my main panel is recessed into stucco on the outside of the house, I don't have a critical loads panel and I have 14.8kW of AC panels. Most true hybird systems want me to re route the AC panels into the inverter (inverter will be mounted in the detached garage with the batteries around 150ft from the main panel) directly and then wire the main panel to it and a critical loads panel and battery.

Skybox says it can do 7.6kW of AC Grid tied and can't be stacked for AC coupling. So seems that is also out.

I have a 100amp panel in the garage that I hope to tie into there and install batteries and inverters wired into that 100amp panel.

I also have looked into automatic transfer switches and such but installing anything like this would require I get with Edison to disconnect power, brake out the stucco on the house and reroute the over head power lines into a new separate meter head (current one it part of the main panel) then run into a transfer switch then off to the existing panel. Unlike alot of installs I see inside the garage taking up a wall mine is all outdoors on the side of the house.

Nice thing about the hybird units is some can do offgrid and phase shift my inverters to stop excess producing but again problem is most have limits on PV size and most are well below my 14.8kW system (been looking at Sol-Ark 12k). Even 2 sol-arks which would cost close to 14k still gonna have a problem. I'm trying not to spend that much money on this project, I hardley ever have a power outage and with net metering and the size of my solar im not paying much in electric and I'll never make up a 20k battery install.
 

not2bme

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Most hybrids are configured to work off-grid. So they show a configuration where there's a subpanel so you are able to function during outages. But it's not necessary if you do not care about this. Also that's why the Skybox has a limit on how big the solar array is, because it has to limit the solar production going through the box. It does this through a frequency shift and is able to stop the production of the solar array otherwise your enphase inverters would just over produce. If the array is too big for the skybox to be able to accept then it won't work either. So either split your enphase arrays into smaller groups or run the PV directly into the skybox.

But you're not using the above in a off-grid situation. You just want to charge from the grid and export to the grid. In that case it doesn't matter that you have to match the PV output. You can have a 3kw inverter, so all you have is you can have a max of 3kw charging and a max of 3kw exporting. If your PV produces 14kw, that means 3kw goes to charging and 11kw goes to the grid. So you 'lose' on the ability to capture the full capacity of PV to the battery. You can technically have multiple different versions and makes of inverters as well, because one doesn't care about the other, since it's charging from grid and discharging to the grid, so as long as it is able to sync to the grid. But I can't really say how well an inverter actually work so I'm just assuming here.

But back to the 14kw array, in order for you to charge all 14kw into the battery, that means you need a battery bank big enough to handle a 14kw charge/discharge. So your battery will also have to be at least able to handle that charging amps. You would be looking at a battery bank that is in the range of 3-6x the size of the pv array as a minimum. But again back to the above, it's not necessary to have an inverter that matches your PV output, unless your end goal is to capture every ounce of power out of the PV.

Also you don't care about split-phase, since if you never need to be offgrid, then 240V output is all you need. The enphase units do exactly that, they don't care about 120V, they output dirctly to 240V. I'm sure the meter doesn't care either if you export only 120V either, since it will just log that you exported x amount but your electric company might because of the imbalance.
 

integlikewhoa

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Splitting of the array is not a task I want to take on. They all come together in a Enphase Combiner box on the main house and connect to the main panel in a 70amp breaker on the main panel on the main house. I plan on installing the battery system and inverters in the detached garage. So running the solar directly into the a hybird inverter (even splitting the array) mean running the the power from the main house roof to the detached rear garage.

I do need to research more on charging the Battery pack. I'm starting out with a 14s200p setup. I do hope to get around 3 of these for around 60kWh of battery but starting at 20 for now.

I'm still thinking the Eltek Flatpack2's wired into my 100amp subpanel in the garage with some type of controller monitoring a CT on the main panel could charge when electricity was flowing into the grid.

I'm thinking of starting out with 2 GTIL2, 2000w each. As I add more battery banks I would probley like to get up to 8kW atleast.

I have electric hot water heater, and Dryer that when running can pull quiet a few watts that I want to make sure can be covered by the grid tie inverters.
 

integlikewhoa

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not2bme said:
But back to the 14kw array, in order for you to charge all 14kw into the battery, that means you need a battery bank big enough to handle a 14kw charge/discharge. So your battery will also have to be at least able to handle that charging amps. You would be looking at a battery bank that is in the range of 3-6x the size of the pv array as a minimum. But again back to the above, it's not necessary to have an inverter that matches your PV output, unless your end goal is to capture every ounce of power out of the PV.

Please help check my math and keep me safe I might be missing somthing.

I never have 14kw maxed of the array. I have east, west and south facing panels and none are perfect sun facing.

I'm looking to use some Flatpack2's to charge and each is around 3kWmax (maybe 60amps on the AC side). If I use 3 that would be around 9kW of DC charging and that should be well below what my 14p200s (2800)cells should be able to handle even at less then 1/2C right?

If I use 4 GTIL2's that's 8kW DCfrom the batterywhich is probley gettings a little closer to less then ideal drain if Imax out all 4 inverters and it stays but thats still well under 1/2C right?

I have a few devices that can pull some heavy loads but all short term. And during the day most loads will pull straight from the AC solar panels the GTIL2's will only kick in if there is any excess loads.
 

daromer

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a 200p setup if we talk about 2nd hand standard cells should not be pressed above your testing current. If thats 0.5A then thats only 100A. 100A at 40V that is minimum is only 4kW. You can do the math there...
At 1A testing you get 8kW max and that is pushing it.

4 GTILS is those 2kW at battery side or grid side?

Yes it might be 1/2C but i cant see that you state what cells you have and how you tested them.
 

not2bme

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It's probably too high to expect to put in 12kw in a 200p pack. I know they do list 1C as the charging amps but it's not recommended. Like daromer said it all depends on the cells you use, if it's old or new, as well as the life expectancy you expect by pushing the cells hard. A general rule I use is that we test at 1A but we run no more than 500ma through it in actual use.

So let's say you run 9kw through the flatpack2, so that's 9000W/(14S*3.7V)=173A. That means with a 200p pack that's 173A/200p = .86A. That's a little too much for what I'd like to do.

That's why I like to size at least 3-6x what your panel size is. So a 14kw PV you'd want something along the lines of a 42kwh battery or more. Just a general rule of thumb.

On the flatpack2, is that a charger that's capable of cc/cv? Or is that just a straight DC power source. Just remember if it's a power source and not capable of limiting the current, the power supply might not like it and disconnect. A lithium requires a cc/cv charging so using just a straight power supply you may be fine bulk charging it, but you may have to disconnect once voltage is reached. Also it's important you can set the final voltage so you don't overcharge the packs.
 

integlikewhoa

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daromer said:
a 200p setup if we talk about 2nd hand standard cells should not be pressed above your testing current. If thats 0.5A then thats only 100A. 100A at 40V that is minimum is only 4kW. You can do the math there...
At 1A testing you get 8kW max and that is pushing it.

4 GTILS is those 2kW at battery side or grid side?

Yes it might be 1/2C but i cant see that you state what cells you have and how you tested them.

Thanks for your info. I'll stick with 2 GTIL2's until i build out atleast one more 20kWh pack. The plan is to get up to (3) 14s200p setups or approximately 60kWh in batteries.

2kW GTIL would be battery side Max.

Cells are Battery Hookup 4 cellModem pack's.


not2bme said:
It's probably too high to expect to put in 12kw in a 200p pack. I know they do list 1C as the charging amps but it's not recommended. Like daromer said it all depends on the cells you use, if it's old or new, as well as the life expectancy you expect by pushing the cells hard. A general rule I use is that we test at 1A but we run no more than 500ma through it in actual use.

So let's say you run 9kw through the flatpack2, so that's 9000W/(14S*3.7V)=173A. That means with a 200p pack that's 173A/200p = .86A. That's a little too much for what I'd like to do.

That's why I like to size at least 3-6x what your panel size is. So a 14kw PV you'd want something along the lines of a 42kwh battery or more. Just a general rule of thumb.

On the flatpack2, is that a charger that's capable of cc/cv? Or is that just a straight DC power source. Just remember if it's a power source and not capable of limiting the current, the power supply might not like it and disconnect. A lithium requires a cc/cv charging so using just a straight power supply you may be fine bulk charging it, but you may have to disconnect once voltage is reached. Also it's important you can set the final voltage so you don't overcharge the packs.

Thanks for the helpful info and general rules of thumb. I'll shoot for the .5 amp per cell.

I'll start with twoFlatpack2's for 6kWfor now and see how that goes I can throttle them down to .5amp a cell until I get atleast another string of batteries in. Probley shoot for 12KW after all (3) strings of batteries are in, but this gives me a goal and ideal number to shoot for.

The Flatpack is a CC/CV and is CANcontrollable by Batrium. I would like them to be fully controlled by Batrium for the saftey, but I also want them to ramp up and down based on excess solar being produced. So that is a task I still need to work on. I might do a basic on/off relay on each of the flatpacks and have them kick on and off one by one as the solar ramps up and down then have Batrium control from there via the CAN bus as they come online. But testing needs to be done.
 

not2bme

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integlikewhoa said:
The Flatpack is a CC/CV and is CANcontrollable by Batrium. I would like them to be fully controlled by Batrium for the saftey, but I also want them to ramp up and down based on excess solar being produced. So that is a task I still need to work on. I might do a basic on/off relay on each of the flatpacks and have them kick on and off one by one as the solar ramps up and down then have Batrium control from there via the CAN bus as they come online. But testing needs to be done.

If you ever find the CAN protocol for the flatpack do post it up here. It's quite interesting to have a cc/cv charger that's 48V capable with high efficiency and high wattage.
 

Roland W

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integlikewhoa said:
Cheap4-life said:
As for your question. Whenever you are selling back to the grid you could instead charge the battery. Maybe you could use a micro controller to trigger a relay to start Ac charger-charging when theres power (more than your loads are using) being fed into the grid Daromer did a video for a dump load and a microcontroller that triggered a relay. Might be helpful.
I'm pretty sure I could trigger a relay for on/off control fairly easy but I was hoping to get more of an amperage control instead if possible. Kind of like the GTIL2 does. it auto ramps up and down based on load it sees coming from the grid to zero out usuage.

I was hoping to to do the reverse for charging the batteries. As amps start flowing out to the grid the charger ramps up until it zeros out or hits max charging to the batteries.

I'm not sure this is possible but looking for ideas.

Thanks,

On my "AC Powerwall project" (https://www.youtube.com/playlist?list=PLz3GU7wMX4_P-K7Ht42iucupu2CXGZh10), i am using 2 small vehicle chargers to reduce excess export to the grid. They are controlled by my self developed microcontroller based board. The information it needs to decide about charging, comes from a SDM meter via modbus (can a SDM120 be as well used in US even its 230V?) Which size of chargers you use is your decision based on available excess power. I live in the 3 phase/230/400V world, but those 230V chargers can run on US grid if you connect to both legs, right. My inverter is the Sun2000. That one can be used in US too. How many of those you use in parallel, is as well your choice. My controller will be soon shown in a follow-up video, and will be available to get as a bare or populated PCB for more or less the price of components.
 

integlikewhoa

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not2bme said:
On my "AC Powerwall project" (https://www.youtube.com/playlist?list=PLz3GU7wMX4_P-K7Ht42iucupu2CXGZh10), i am using 2 small vehicle chargers to reduce excess export to the grid. They are controlled by my self developed microcontroller based board. The information it needs to decide about charging, comes from a SDM meter via modbus (can a SDM120 be as well used in US even its 230V?) Which size of chargers you use is your decision based on available excess power. I live in the 3 phase/230/400V world, but those 230V chargers can run on US grid if you connect to both legs, right. My inverter is the Sun2000. That one can be used in US too. How many of those you use in parallel, is as well your choice. My controller will be soon shown in a follow-up video, and will be available to get as a bare or populated PCB for more or less the price of components.

Thank you seems your project is very similar to what I'm trying to accomplish. I have started to watch your videos but have a bit more to go. Thanks for the info.
 

Hamalot

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Hi, new member here. I have exactly the same query as you integlikewhoa, but for slightly different reasons. Did you find an answer? I'd be very interested to hear how far you got with your research. I built my own power diverter so that excess solar is sent to my immersion heater through a PWM controller. Excess power is measured by a Shelly EM and the PWM regulator is countroller by a Shelly Uni. I feel like i should be able to replicate this somehow to divert to batteries but i don't know much about charging batteries. I don't know if i can run a PWM AC voltage into a dc transformer an than into a solar/wind charge controller (it's used to seeing power fluctuations on the input right?)? Any thoughts appreciated. Very happy to share more details on my setup if it will help.

Roland W, i've had a look through your videos and it looks like you are using relays to turn your chargers on/off rather than modulating based on available power?
 

ajw22

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A somewhat different approach using mostly off-the-shelf WiFi products:

I have a IoTaWatt clamped on my main breaker box. A RaspberryPi continuously queries how much power I'm exporting, and then switches off/on several TPLink HS105 SmartPlugs to de-/activate various dump loads. Easy to control a AC charger with this. Probably best to use several lower power ones to more finely track the amount of excess power.
I can post more details if you find this interesting.
 
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