Testing a Microinverter Running on Battery
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- เผยแพร่เมื่อ 6 ต.ค. 2024
- In this Solar Power DIY Helpdesk video, I'm going to be testing the idea of operating a Hoymiles HM-350NT microinverter as a grid-storage inverter powered by a LiFePo4 battery bank, 26Vdc, 50Ah, PowerQueen. Unfortunately, the battery voltage is not high enough for this microinverter to operate within its DC input specification. I'm awaiting one and two more batteries to try 38V and 50Vdc.
I am also awaiting the arrival of the CCS WND meter required to test the export control of the inverter. Stay tuned!
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I've been running a second-hand Enphase 215W micro-inverter with a single 265W PV panel and 3 x reclaimed (free) Dyson 6S batteries in parallel (faulty units with new BMS). The batteries charge slowly from dawn (panel facing West) via a high current Schottky diode. At about noon, the batteries are full and the BMS switches off. The mains is switched on through a timer at 12:30, so the panel is then feeding the inverter for the rest of the daylight hours. At dusk, a light sensor switches the batteries (via high power MOSFET) to the inverter giving about 40 minutes run time at over 200W. The mains timer switches off at midnight. This has been working perfectly for about 3 months so far.
If the micro is connected directly to the battery, what is the DC input current and does it exceed the input current rating of the micro?
@@DiySolarHelpDesk The maximum operating input current of the Enphase M215 is 10A, and it seems to limit itself to that. Bear in mind that these are old batteries and are about 25V fully charged, quickly dropping when loaded. I did contemplate using 7S Dyson batteries, but I think that may be too much. It's been running for over 3 months with no issues, so it seems to be happy.
Hello Andy, how has your setup been running? Are you connecting the panel, battery, and inverter in the same circuit? Thanks
@@deyumei7965 It's still running well. I use MC4 splitters to connect the battery unit across the feed from the panel to the inverter, so it's easy to disconnect the battery when required. I remove the battery during the coldest months.
very very interesting
I am working on a new product to make a battery behave like a solar panel, and limit the current to within the microinverter's spec. It will pre-charge the capacitors, provide a low battery cut-off, and automatically restart when charged. When used with the WattNode meter, it can do zero-export time-shifting, energy arbitration and peak shaving. It's almost ready for Beta testing. (877) 58-SOLAR.
@@DiySolarHelpDesk In this way don't you lose the mppt alghoritm features? and what do you think about use for example a Renogy dcdc battery charger il parallel to the hoymiles micro grid input?
@@sebaberny7170 MPPT doesn't matter when working from a battery, but this keeps the current below the limit. You can use any battery charger.
That was interesting , i was thinking of getting a Hoymiles microinverter , iv only got 3 240 watt panels in garden on garage roof, one question please , dose the Hoymiles microinverter need the gateway to wake them up like the enphase dose ? or dose it work straight out of the box ?
Great question! They work straight from the box. As close to a Plug-n-Play solution as there can be. The Data Transfer Unit (DTU) for monitoring is optional, and only around $300. If you want to discuss more and create a plan, I'm available daily at (877) 58-SOLAR. Thank you.
@@DiySolarHelpDesk That's great many thanks for that information ,that i couldn't get anywhere .I'm living in the UK so i guess i'll have to take a look at seller here ,so far only found Germany .
Interesting! Do you know whether an APsystems EZ1-M can be hooked up directly to a 48 V battery?
I haven't tested it, but it should work if you pre-charge it before connecting the battery.
@@ToddDesiato Thanks for the quick reply! I've read many comments in the meantime and some say that a 48 V 50 A capable battery would likely 'fry the inverter'. Is this something to worry about? When I chose micro-inverters for my PV setup, I made sure they wouldn't cap the max. power output of the solar panels. So based on that I know a micro-inverter will probably limit the current inflow from a battery by design, but naturally I'm looking for safety first.
On a side note: I like the modular concept of micro-inverters, for one you don't have a single point of failure and it's better scalable. In the Netherlands there is a company called HomeWizard who have picked up on this principle in the context of battery storage and they're actually launching their _Plug-In Battery_ which is basically a cost-effective AC-coupled design: www.homewizard.com/nl/plug-in-battery/
This 2.7 kWh battery storage unit can be plugged into any normal wall socket and will charge/discharge at 800 W max. which is within European regulations. People will be able to use more than one of these and then 'software unlock' the batteries to effectively operate in parallel (so 2 batteries at 1600 W charge/discharge and 5.4 kWh energy capacity etc.).
For sure they're using a micro-inverter in this device, the big question is what they've done to make it battery-compatible, if anything.
Can from battery to microinverter using the dc to dc converter to regulate the voltage and low the output amp
Look at some of the earlier videos where I tried this. Yes, it works but the dc to dc converter is unstable. The frequency varies all over the place due to the 120Hz ripple current pulled by the inverter. The HMS-500-1T-NA can connect directly to the battery and you use a DTU, and a meter with RS485 to control the output.
@@ruslanwel Did you use the resistor in your circuit?
@@ruslanwelwhat issue did you have when using the DC-DC converter？I am thinking about the same setup but I am going to use it daily It seems like drawing power from the battery will make it run at its maximum output continuously and it's not designed for that. Do you have any tips or suggestions ？Thanks
How about simply adding configurable BMS to limit the current?
It would make the BMS run hot, but it will work I think. I don't have one to try it.
@@ToddDesiato The BMS could be oversized and run it only i.e. at 50% rate to keep it cool(er).
@@KenSentMe- With that configuration, you would need a BMS for each microinverter. I just need a couple of resistors and a MOSFET. I have boards designed, but now I have Hoymiles Hybrid inverters HYS series on order. I don't need this anymore.
Im confused. so can microinverter run directly from battery or not? withouth the resistors? Thanks
This one cannot, because it will exceed the Isc rating of the 350W inverter MPPT inputs. However, the HMS-500, 1000, and 2000, can run directly from a 48-56 Vdc battery. The limit is 25A. It's just not covered by the warranty if it fails.
@@ToddDesiato Hello Todd, I recently came across a discussion online about the Enphase microinverter and its resistance fault check during startup, which requires detecting a certain resistance to function correctly, potentially preventing it from operating if the power comes directly from a battery. Do you think the HMS microinverter doesn't have that resistance fault check and that's why it worked? I am trying to set up a circuit like this to off-set my peak hour use during afternoon, do you think it will work in long terms? Thanks!
@@ToddDesiato How about the APsystems EZ1-M/H?
I've got an HMS-350, I plugged It to a 24v battery and It's fried now. Probably i'd to use a resistor. Waiting for the reparation. I'm assuming of using the LOAD output of a mppt to Power up the inverter. Somebody have tried It?
Hello, I am very interested in your test. My question is if the maximum DC current supported by the microinverter is 15 amperes, how does it happen that the inverter does not burn, taking into account that the batteries can discharge much more than 15 amperes (50 amperes)?
They self limit. Inverters control the current they take in, as long as the voltage isn't too high.
@@Theaveragenerd2000 I think it's the first microinverter I've heard of that limits its input current by itself. All the others would have burned out instantly.
Starting from 09:10 we see a pair of high-power green resistors that appear to be in series with the batteries on the microinverter DC input. I think those resistors are limiting the DC input current.
The current shown at time 0:53 is 30A peak. This is what the micro will draw if there's nothing to limit the current but itself. It draws what it needs to deliver full power. In the case of a PV module, the Isc is about 10A for a 400W module, so the current could NEVER go to 30A. This was making the fuse and the wire get hot so I discontinued the test. I then tested it with a buck converter which was somewhat unstable. It worked but I would need to design one myself to get it to mimic a solar panel correctly. I then tried the 2 Ohm resistor and the 2X 0.2 Ohm resistors (0.4Ohms). They limited the current but not enough. The maximum rating of the micro is 11.5A dc. I find that if It runs at 46Vdc and above, using my power supply, then the input current is ideal with just the 0.4Ohms, but I am going to try a SIC JFET because that will dissipate less power and provide a hard current limit at 10A. A buck converter would be the most efficient solution, but I haven't designed one in decades. The chips I used to use can't be found anymore.
@@Theaveragenerd2000 Eventually. The meter on the bench is for export-control and var-control. The inverter can accept DER commands to throttle back the output power, thereby drawing less input current. I haven't tested it because the meter I have is not the right one. It didn't communicate. I ordered the right one, it will ship on 8/23.
hm. Im waiting for parts for doing the same test but with yc100 and with a 48vdc/55Ah battery bank but as i didnt understand from the video is how you made the calculation for the resistor as the current limiter... the microinverter i will test got 14.6ADC*4 inputslines working between 22-60VDC. How did calculate the 2ohm and 0,4ohm values?
Thank you. As of today, I also have a 48Vdc/50Ah setup. I estimated the resistance of a 400W module to be about 0.8 Ohms. I bought 4 x .2 Ohm resistors, 100W each because they were cheap and available. As an alternative to the resistors, tomorrow I will receive an isolated DC-DC converter with a 10A maximum current at 48V, so there is no need for the resistor, in theory. We shall see. I also just received the correct CCS WattNode meter that should work for export control. Fun times coming in the next couple of days!
@@ToddDesiato thanks for the reply, now i understand what you refering to. Tomorrow i get my stuff to complete the setup. I was thinking of using a maximum power point tracker device to reduce the current to 14,6ADC-ish. Is that what you have in mind with dc-dc converter 48VDC/10A or did you find something else useful? As i know, a dc/dc does produce some heat.
@@gooseberry46 Turns out, the DC-DC converter shuts down without any resistance. The microinverter will draw 13A, which exceeds it's current limit so it shuts down. When I added the 0.2 Ohm resistor in series, it worked fine. The MEAN WELL SD-500L-48 will accept an input range from 19-72 VDC, so it makes this compatible with just about any battery 24, 36, 48, 60V.
Then I removed the DC-DC converter and just used the 0.2 Ohm resistor in series with a 15A fast-blow fuse, and the 48V battery bank. It also works fine. I'm going to design a circuit board with an automatic pre-charge resistor and MOSFET, and the 0.2 Ohm resitor and a current limit shutoff. Then, this can be integrated with any microinverter.
I needed to get the firmware updated in my DTU, but the meter works and I now have a working peak-shaving energy storage system!
@@ToddDesiato well, i got my package and can see it isnt what i thought it was. So im delayed...
@@gooseberry46 I don't know what you got, so... I'm curious. I just got my DC breakers so I can set up more than one inverter. I just need to mount another resistor on a heatsink. It's fun!
Very smart!! I NEED HELP :)
What is your email?