newbostonconst
Solar Enthusiast
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Using solar micro inverters with batteries instead of panels
- Thread starter chopwood
- Start date
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.
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.
twrlp
Solar dabbler
37 ohms seems odd. Do you still see that reading when connecting the smaller (working) pack?
icenov
New Member
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.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.
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 wonder if this could be the reason for standards specifying the fire rating of the inverter backing and location????
timselectric
If I can do it, you can do it.
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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.
icenov
New Member
I think this is just poor quality control, as it could have just as easily been the power cord on an appliance like a PC or television.
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 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.
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.
silverlexg
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Mark - Can you detail how you are charging the batteries? Do you have other enphase microinverters for your solar production? Are you able to dyynamically control charge rate? otherwise i'd be worried about limiting PV production when you have an excess of power but the envoy limiting production. Would you be able to have 2 envoys? one for PV production and one for your battery inverters. I'm looking to do the same setup (powering micro inverters via battery during the night to cover the base house load to timeshift without expensive re-wiring. I'm looking to use the common 48v rackmount lithium batteries.
kundip
Micro Inverter Enthusiast
Mine is similar. I have 1 Envoy micro inverter per battery. You can have as many micro inverters as you like.
I have one 24V Battery with 5KW AC capacity running every night for 14 hours @ 300W AC (240 V)
Also one 24V Battery with 1.6KW AC Capacity running every night for 14 hours @ 200W AC (240 V)
Because my system is Micro Inverters everything is 240V AC.
So I charge my batteries during day with good quality 240V chargers.
I don't like the chargers that do everything (AGM, Lead Acid, LiFePo Etc - all in one) (I use Dedicated only)
AC-DC 24V 20A Lithium LiFePO4 Battery Charger - Amptron
AC-DC 24V 20A Lithium LiFePO4 Battery Charger AMPTRON® Lithium Iron Phosphate (LiFePO4) battery chargers are state-of-the-art battery chargers with a charging profile specifically designed to charge and maintain Lithium Iron Phosphate (LiFePO4) batteries, and can safely achieve a 100% State of...
www.amptron.com.au
I charge about 8 hours per day.
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silverlexg
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Kundip - thank you for responding! Are you using an envoy to limit output from the battery or have you basically just assumed 1 microinverter with constant output for the whole evening? How are you controlling the charger? I know you can limit over/under charge on the battery via BMS but do you have some logic somehow setup to turn the charger on if over producing solar? How do you disconnect it in the evening once your PV power is gone? Appreciate the info - This really seems like a simple way to timeshift solar production into the evening hours.Mine is similar. I have 1 Envoy micro inverter per battery. You can have as many micro inverters as you like.
I have one 24V Battery with 5KW AC capacity running every night for 14 hours @ 300W AC (240 V)
Also one 24V Battery with 1.6KW AC Capacity running every night for 14 hours @ 200W AC (240 V)
Because my system is Micro Inverters everything is 240V AC.
So I charge my batteries during day with good quality 240V chargers.
I don't like the chargers that do AGM, Lead Acid, LiFePo Etc. (I use Dedicated only)
20Amp is a bit slower but the whole system runs quite cool.AC-DC 24V 20A Lithium LiFePO4 Battery Charger - Amptron
AC-DC 24V 20A Lithium LiFePO4 Battery Charger AMPTRON® Lithium Iron Phosphate (LiFePO4) battery chargers are state-of-the-art battery chargers with a charging profile specifically designed to charge and maintain Lithium Iron Phosphate (LiFePO4) batteries, and can safely achieve a 100% State of...
I charge about 8 hours per day.
kundip
Micro Inverter Enthusiast
I am grid connected. Any excess power from panels or batteries (minimal) goes to grid.
Trying to balance on your own excess power is too expensive & complicated. IMO
I use 240 Volt dedicated battery changers instead of solar chargers as I think they are better suited to charging LiFePo4 or any other batteries. IMO
A lot of the solar inverters that charge batteries do not do that good a job. IMO
My system is designed to use any battery that I buy cheap on local sites AGM, Lithium whatever & match charger to it.
For example high end Amptom Lithium batteries cost AUD $1,859 each NEW
I got two for AUD $800 each. (1 & 1/2 Years Old) to use. My payback time is under three years.
There may be some inefficiencies using a 240V charger but I just add more panels, with micro-inverters, to adjust the loss.
I buy the envoy micro-inverters for AUD $30 second hand. Other parts cost AUD $200 all up.
Each system costs about USD $700 all up.
I have three of these systems working flawlessly for over a year.
I now produce 900 Watt @ 240 V AC for 14 hours per night.
200 watts per inverter may not seem like a lot but it makes a big difference to your energy independence.
My picture in last post shows energy dependence is only 17% from grid.
This year 2023 so far my energy dependence is only 8% from grid.
I work small but get big results. IMO
Nothing is complicated & all is easily managed & maintained.
Please note my original design shows a buck converter - this is not required.
Added 14/04/23: PLEASE NOTE - I no longer use buck converters nor advocate in this situation. See my later posts.
Trying to balance on your own excess power is too expensive & complicated. IMO
I use 240 Volt dedicated battery changers instead of solar chargers as I think they are better suited to charging LiFePo4 or any other batteries. IMO
A lot of the solar inverters that charge batteries do not do that good a job. IMO
My system is designed to use any battery that I buy cheap on local sites AGM, Lithium whatever & match charger to it.
For example high end Amptom Lithium batteries cost AUD $1,859 each NEW
I got two for AUD $800 each. (1 & 1/2 Years Old) to use. My payback time is under three years.
There may be some inefficiencies using a 240V charger but I just add more panels, with micro-inverters, to adjust the loss.
I buy the envoy micro-inverters for AUD $30 second hand. Other parts cost AUD $200 all up.
Each system costs about USD $700 all up.
I have three of these systems working flawlessly for over a year.
I now produce 900 Watt @ 240 V AC for 14 hours per night.
200 watts per inverter may not seem like a lot but it makes a big difference to your energy independence.
My picture in last post shows energy dependence is only 17% from grid.
This year 2023 so far my energy dependence is only 8% from grid.
I work small but get big results. IMO
Nothing is complicated & all is easily managed & maintained.
Please note my original design shows a buck converter - this is not required.
Added 14/04/23: PLEASE NOTE - I no longer use buck converters nor advocate in this situation. See my later posts.
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zalamandern232
New Member
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diy06.JPG, this look like what im trying to do but i working with 48vdc battery bank, does your setup still work? I cant see any fuses to protect the batteries or the inverter, how do you current protect the circuit? how high is your current when you start the setup?
kundip
Micro Inverter Enthusiast
Yes I have 15 amp fuses at the battery
zalamandern232
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ok, you use the one on the dc/dc converter. Somehow my fuse seems allways to blow
tried lower the current limiter to what i guess, is half. will try to use a powerresistor
kundip
Micro Inverter Enthusiast
Lowering the current is very hard.ok, you use the one on the dc/dc converter. Somehow my fuse seems allways to blow
I have found I can do without the buck converter since my last post.
The Enphase microinver itself only pulls 10 amp 24v DC and puts out 240v @ 200 watts per hour.
It should do same at 48v. I picked 24v originally because there are many more devices available at that voltage. (& Cheaper).
48v is catching up but dearer. IMO
I have put a 24v 30amp relay & power the inverter through that. I don't run the main current through the Victron Battery Saver any more as I had too many problems with the Victron even though it is rated at 65amp. It kept on complaing about "inrush current" or just cut the voltage from 24v to about 8v.
I use the Victron to turn on and control the relay.
The Victron cuts off battery @ 24v.
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Did you ever get a working DC-DC boost converter and how did it work out for you feeding battery power to your Microinverter after sunset?I wouldn't do it! (but I think there is a solution...)
In the best case, the MPPT algorithm of the microinverter would never lock, and output would fluctuate.
In the worst case it would simply fry your microinverter and/or ruin your batteries.
There are some grid-tie inverters that are actually designed for this (like the SUN 2000W) , but I don't know of any microinverters that have this feature.
What the MPPT algorithm is looking for is a maximum power point. With batteries, the maximum power point is theoretically infinite.
But, maybe you can use one if these DC-DC boost converters in betweenyour batteries and the microinverter, which has a current limiting function.
For example, lets say you set your DC-DC converter to a maximum of 15 amps and 36v. If the microinverter will try to pull more than 15amps, the DC-DC will lower the voltage accordingly. The MPPT should then understand that it went too far with the current and slowly bring it down.
All this is in theory, I haven't tried it, but I did play with some of these DC-DC boost converters. They are pretty nice and cheap, but a bit if a pain to setup (using pots to set voltage and maximum current).
I would suggest you get one and experiment slowly. I would set the maximum voltage a bit less than your microinverter's maximum voltage, and the amps at almost the maximum the microinverters can handle.
But make sure that this is inline with your batteries abilities and your wiring guage.
If you set it properly, it should protect your batteries a bit, but still I would add proper fusing just in case.
There are different versions of these cheap DC-DC boost converters, but I would get the 1800w one, just because it has a temperature controlled fan, and its beefier.
These guys generate heat at high loads, so make sure to keep them indoors and properly ventilated.
18.34US $ 30% OFF|Dc-dc Constant Voltage Constant Current Boost Converter 1800w 40a 10-60v By Fan For 12-90v Boost Power Module Step Up Adjustable - Voltage Regulators/stabilizers - AliExpress
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Good luck... and stay safe.
I just purchased one of these and am interested in anyone’s experience using these budget programmable current-limited DC-DC boost converters to limit output from a Microinverter when powering from a battery…
kundip
Micro Inverter Enthusiast
Using solar micro inverters with batteries instead of panels
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...
diysolarforum.com
Trying to balance on your own excess power is too expensive & complicated. IMO
I use 240 Volt dedicated changers instead of solar chargers to charge batteries when the sun is out as I think they are better suited to charging LiFePo4 batteries. IMO
A lot of the solar inverters that charge batteries do not do that good a job. IMO
My system is designed to use any battery that I buy cheap on local sites AGM, Lithium whatever & match a good charger to it.
For example two high end Amptom Lithium batteries I have cost AUD $1,859 each NEW
I got two for AUD $800 each. (1 & 1/2 Years Old). My payback time is under three years.
There may be some inefficiencies but I just add more panels, because I use micro-inverters, to adjust the loss.
I buy the envoy micro-inverters for AUD $30 second hand. Other parts cost AUD $200 all up.
Each system costs about USD $700 all up.
The first one has been working flawlessly for over a year.
The second 6 months.
My third one will be in production in a couple of weeks.
200 watts @ 240 volts may not seem like a lot but it makes a big difference to your energy independence.
My picture in last post shows energy independence as 83% meaning only 17% from grid.
I work small but get big results. IMO
Nothing is complicated & all is easily managed.
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Hedges
I See Electromagnetic Fields!
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Please do not link to web pages promoting your business.
That is against forum rules.
You should edit your posting to delete the link.
Uhhh, don’t get that. This is grid-tied, so any energy you output shaves load and no need to size the battery bank to anything other than the amount of load you want to shave while the sun is not shining…
Well if you want to attempt direct connection of battery to Microinverter (which I do not advise), then yes, you need to assure that the MPPT range of the Microinverter brackets your battery voltage.
But if you use a DC-DC booster as proposed by the OP in between the battery and the Microinverter, all you need to do is assure your Microinverters max MPPT voltage exceeds to batteries maximum fully-charged voltage…
A good reason to go with LiFePO4 rather than Lead Acid (or it’s variants).
I just ordered one of the same budget DC-DC boosters as purchased by the OP to try exactly that. Will report back on what I find…
Hedges
I See Electromagnetic Fields!
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And you have a way to stop discharge at low Vbat, not over-discharging.
If the battery has BMS which can disconnect, we recommend that be protection when other controls malfunction, not first line of defense.
Absolutely. These budget programmable DC-DC converters supposedly also include programmable low-voltage protection, but that’ll be one of the first things I characterize (assuming I decide they are capable enough to warrant the investmevt).
Of course, as a fall-back, a battery voltage monitor can always open an AC relay connecting to the Microinverter output…
Good catch.
I didn’t bother to follow the link but the New Member with 3 posts should have been a tip-off…
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