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Using solar micro inverters with batteries instead of panels

I'm also interested in using a battery powered microinverter instead of solar panels. The main reason is I've got a 5 kWh lead-acid battery from my ride on mower that is in the process of being replaced with LiFePO4 as per this thread.
So instead of wasting the capacity I am going to use it to provide an additional 5 kWh to my existing 10 kWh home battery. But the problem is that I can't connect another DC input - or mix battery types - into my existing system.
I received my 600 W grid-tie inverter today and hooked it up to the 52 V LiFePO4 battery back and so far all seems to be working as expected. I don't think you need to worry about frying the inverter using a battery, as it will limit the input current to whatever is needed for the max output.
In my case, the battery pack is about 50% SoC, with voltage at about 51 V.
Some photos of the system:
LiFePO4pack.jpgbms3.jpg
Note this is the mower battery pack waiting for a box etc. I'm using a Daly BMS with bluetooth, and a separate shunt/voltmeter in series.
I had to find a microinverter that could take up to 60 VDC as the LiFePO4 pack fully charged is about 58 V. Most others have a maximum of 55
or less.

volt_micro.jpginverter.jpg
As you can see from the screen capture, the battery pack is discharging at 641 W, so allowing for losses, I expect the microinverter is outputing 600 W. I see that occassionally the battery current changes from 12 A a bit (up to 12.5, down to 11.5).
So after operating for about 60 mins - so far all good!
 
I could not perform the test as explained in the originary post due to suspected defective DC-DC buck converter. (Buying at Aliexpress is tricky...)
I also wonder If an undersized battery could be used for such test even If just for a few seconds. Without current limiting, the test seems risky; not for the inverter but for the battery.

https://diysolarforum.com/threads/testing-grid-tied-inverter-with-battery.32173/

I will try this week the inverter with the solar panels, but this is no new stuff to you. In 1,5 months I will receive another buck inverter, maybe this one is good and I can use it for the test.
Following you on this with interest.
I am waiting on two buck converters from Amazon and one from Alibaba.
Both listed in my previous threads.
So by the looks I may be testing before you.
As I have already fried a local $Aus15 - 3 Amp Buck Converter that was too small.
There will be protective fuses on any more Buck Converters I use in the hope that I won't incinerate them.
 
I'm also interested in using a battery powered microinverter instead of solar panels. The main reason is I've got a 5 kWh lead-acid battery from my ride on mower that is in the process of being replaced with LiFePO4 as per this thread.
So instead of wasting the capacity I am going to use it to provide an additional 5 kWh to my existing 10 kWh home battery. But the problem is that I can't connect another DC input - or mix battery types - into my existing system.
I received my 600 W grid-tie inverter today and hooked it up to the 52 V LiFePO4 battery back and so far all seems to be working as expected. I don't think you need to worry about frying the inverter using a battery, as it will limit the input current to whatever is needed for the max output.
In my case, the battery pack is about 50% SoC, with voltage at about 51 V.
Some photos of the system:
View attachment 74876View attachment 74877
Note this is the mower battery pack waiting for a box etc. I'm using a Daly BMS with bluetooth, and a separate shunt/voltmeter in series.
I had to find a microinverter that could take up to 60 VDC as the LiFePO4 pack fully charged is about 58 V. Most others have a maximum of 55
or less.

View attachment 74878View attachment 74879
As you can see from the screen capture, the battery pack is discharging at 641 W, so allowing for losses, I expect the microinverter is outputing 600 W. I see that occassionally the battery current changes from 12 A a bit (up to 12.5, down to 11.5).
So after operating for about 60 mins - so far all good!
Most interesting.
Looks really good.
Fingers crossed you get long term usage with minimal or no breakdowns.
Lead Acid are too heavy for me.
 
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I'm also interested in using a battery powered microinverter instead of solar panels. The main reason is I've got a 5 kWh lead-acid battery from my ride on mower that is in the process of being replaced with LiFePO4 as per this thread.
So instead of wasting the capacity I am going to use it to provide an additional 5 kWh to my existing 10 kWh home battery. But the problem is that I can't connect another DC input - or mix battery types - into my existing system.
I received my 600 W grid-tie inverter today and hooked it up to the 52 V LiFePO4 battery back and so far all seems to be working as expected. I don't think you need to worry about frying the inverter using a battery, as it will limit the input current to whatever is needed for the max output.
In my case, the battery pack is about 50% SoC, with voltage at about 51 V.
Some photos of the system:
View attachment 74876View attachment 74877
Note this is the mower battery pack waiting for a box etc. I'm using a Daly BMS with bluetooth, and a separate shunt/voltmeter in series.
I had to find a microinverter that could take up to 60 VDC as the LiFePO4 pack fully charged is about 58 V. Most others have a maximum of 55
or less.

View attachment 74878View attachment 74879
As you can see from the screen capture, the battery pack is discharging at 641 W, so allowing for losses, I expect the microinverter is outputing 600 W. I see that occassionally the battery current changes from 12 A a bit (up to 12.5, down to 11.5).
So after operating for about 60 mins - so far all good!

Well, things are about to get interesting now. We have just received the same inverter (just different label on it but clearly same model). I am waiting for the current meters (DC) to start analyzing the performance, the starting power and other parameters of the inverter.

1638868676167.jpeg

As kundip mentioned in a separate post, the inverter can be used on battery mode so long the voltage is over the MPPT range and below the max. input voltage, so 51V is a good spot. But icenov, be careful with running the inverter at full capacity; in some videos of solar youtube guru's it is mentioned that running these chinese inverters at full capacity for hours will significantly reduce their lifespan. I bought it for 2S 16V solar panels and testing with battery may happen or with 12S 2P 18650 battery so I can surpass the 48V from the MPPT range or after I receive a new DC-DC buck converter (which actually can't go over the 48V, so... hope is no problem).

At the same time I am waiting for another MPPT grid tied inverter for a 12V battery and 1 single 12V panel. This is a primitive version of a hybrid inverter and can be used or as a MPPT grid tied inverter from the solar panel or as a grid tied inverter from a battery with regulated discharge [60-250W] (MPPT function off). Both ways of operating can not be used simultaneously. Why I say this is a primitive version of a hybrid inverter is because this ones can operate both mechanisms at the same time while also having much better ranges and often some LED screen or wifi app for smarter programming.



H5eb7aa4e635943b9a72d3116f6ef632dH.png
 
Yes, interesting! I wasn't aware that there was a battery input option available. I did check the starting current draw of the inverter, and it rose slowly from zero to 12 A over about 30 seconds. There is also an adjustment screw for the MPPT range, but no mention of what it does in the manual...
 
I reconfigured my battery pack and now have 550ah pack 20 cells 66 volts. This caused my IQ7x give a red light which in the manual states "DC Resistance Low"

The pack I did the testing on with hooking the IQ7x to a battery was done with a 55 ah pack and I have also hooked it to a larger pack and it worked but now with the big pack it isn't....

Just wanted to let people know so they don't waste money.....
 
I have ran an IQ7x on 24 volts to almost 70 volts increasing one cell at a time.

So how this micro inverter works running it connected to a battery:
It started making power at 33 volts.
It always pulls right around 6.15 amps.
So at 33volt x 6.15amp = 203 watts
Thus at 50 volts x 6.15amps = ~245 watts
It maxed out at 53 volts x 6.15 amps = 326 watts
It makes 326 watts at all voltages above 53 volts.

I never have seen the wattage drop when warm like the specs say....I ran it at room temp.
This was done with a 55 ah pack.
 
I reconfigured my battery pack and now have 550ah pack 20 cells 66 volts. This caused my IQ7x give a red light which in the manual states "DC Resistance Low"

The pack I did the testing on with hooking the IQ7x to a battery was done with a 55 ah pack and I have also hooked it to a larger pack and it worked but now with the big pack it isn't....

Did the 550ah battery happen to share a common/bonded ground with your AC system?
From what I’ve read the iq7 design relies on an isolated DC.

(Following this thread as I’m considering the same approach with iq7x + a 100AH battery)
 
Just came across a relevant video suggesting feeding the inverters above their MPPT range in order to inhibit V/A-seeking competition between multiple inverters connected to the same source.

 
Just came across a relevant video suggesting feeding the inverters above their MPPT range in order to inhibit V/A-seeking competition between multiple inverters connected to the same source.

While feeding the inverter with a battery outside of the MPPT range is probable the best option, I can add that I have recently fed a MPPT inverter with a battery within the MPPT range and it has not caused any apparent issue. Also, not sure If as result of the MPPT function, the inverter has not pulled the full load on the battery (small one; 8S2P 18650 cells) which suggests the MPPT found a stable power point even for the battery. The inverter I used is (600W):
1639982542939.png

The only inconvenient is that the power point was still a bit high and as result, I had to disconnect the batteries after 20 minutes to avoid overheating.

After x-mass season I am planning to upload a video about it. It is a test I can repeat many times.
 
Did the 550ah battery happen to share a common/bonded ground with your AC system?
From what I’ve read the iq7 design relies on an isolated DC.

(Following this thread as I’m considering the same approach with iq7x + a 100AH battery)
I checked resistance to both battery terminals and the Negative was pretty much open but the Positive was like 37 ohms. Odd to me. The IQ7x was not connected to ground and was just sitting on a plastic box. Still in test mode....I might try connecting ground or any other thoughts?
 
I'm using enphase M215 micro inverters with 6 Valence U27-12XP batteries (2S-3P) and the inverter are connecting and produce max possible power without any problem.
The current is automatically adjusted to match the decreasing voltage. I use this to store excess daily production and use it to cancel the "backgrounf noise" during the evening and the night. So no need to regulate the output, the max power is lower than my permanent grid consumption.
 
I checked resistance to both battery terminals and the Negative was pretty much open but the Positive was like 37 ohms. Odd to me. The IQ7x was not connected to ground and was just sitting on a plastic box. Still in test mode....I might try connecting ground or any other thoughts?

37 ohms seems odd. Do you still see that reading when connecting the smaller (working) pack?
 
Well, things are about to get interesting now. We have just received the same inverter (just different label on it but clearly same model). I am waiting for the current meters (DC) to start analyzing the performance, the starting power and other parameters of the inverter.

View attachment 74885

As kundip mentioned in a separate post, the inverter can be used on battery mode so long the voltage is over the MPPT range and below the max. input voltage, so 51V is a good spot. But icenov, be careful with running the inverter at full capacity; in some videos of solar youtube guru's it is mentioned that running these chinese inverters at full capacity for hours will significantly reduce their lifespan. I bought it for 2S 16V solar panels and testing with battery may happen or with 12S 2P 18650 battery so I can surpass the 48V from the MPPT range or after I receive a new DC-DC buck converter (which actually can't go over the 48V, so... hope is no problem).

At the same time I am waiting for another MPPT grid tied inverter for a 12V battery and 1 single 12V panel. This is a primitive version of a hybrid inverter and can be used or as a MPPT grid tied inverter from the solar panel or as a grid tied inverter from a battery with regulated discharge [60-250W] (MPPT function off). Both ways of operating can not be used simultaneously. Why I say this is a primitive version of a hybrid inverter is because this ones can operate both mechanisms at the same time while also having much better ranges and often some LED screen or wifi app for smarter programming.



H5eb7aa4e635943b9a72d3116f6ef632dH.png
I've used my grid-tie inverter about 10 times so far and it has worked well, but the other day I got a bit of a nasty surprise. While working near the inverter on my bench, I needed to move the AC cable and picked it up - it was really hot! The plastic was sticky in one area and I immediately switched it off. I couldn't believe it was due to excessive current as it is only rated at 600 W, and it was delivering about 450 W at the time.
I removed the AC cable and sliced off the outer plastic insulation over the area it was hot. See the attached photo.
It looks like the conductor has corroded and freyed. This could have started a fire if it got out of control.
I've replaced the AC cable with a new, more robust unit - but I've learned a lesson....
 

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I can't remember if it's emphase or some other company. But this is how their battery banks are connected.
 
Hi, Bring up a older post but would love to hear more about how this is working out for the @chopwood.

I would like to do similar and are thinking of the Enphase Micro Inverters S215/S230. This can be connected togeather with batteries. With the use of the gateway I would have export control to the AC Grid . This would mean the batteries are ever only suppling what is required at the time.. I wouldn't need any AC relays to control the output load in this case. My idea would be to fuse each Micro with a 2pole MCB and Fuse each MC4 then connection the micro inverters to a 10-20kwh of scooter batteries storage.

I have read some people are concerned with shorting of connecting micro inverters to the same battery and others say there is not a problem.. I'll fuse to be safe and limit total AC output to 10amps / 2400w.
 
I just tried this with Enphase IQ7 powered from current regulated power supply. It works from 14.1V to 47.8V DC input (>22V to startup) and maxes out at 10A below 25.5V. Max AC output is 244 watts.

This is perfect and just what I was looking for to enable dumping excess energy from my experimental offgrid battery bank into grid powered house loads. I need to set up some automation to apply DC when house air conditioner comes on or my EV starts charging. I could set up one IQ7 to run continuously and discharge 6.12 kWh DC per 24 hours and never run the grid meter in reverse because house loads are always more than 250W. And I could add 3 or more IQ7 to come on sequentially as house loads increase. Controlling them could be done by switching DC input to each inverter via MOSFET switches with precharge resistor path.
 
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I have been using m230 micros with 36v esccoter batteries and it works well. I tried to control the micros by automating on and off ? They take to long to start up and they are not efficent. My best move was to buy from ebay the envoys gateway? Now I leave all the micros on and the controller matches the generation to house demand. i use the zero export profile. Now no wasted generation? I have the batteries charged from mains on free power hours.
 
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