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Looking for an AC coupled battery inverter with output power control
#21
Not sure yet if this applies in your case - but one of the *key* reasons to avoid unapproved grid-tie is that you could accidentally energize the lines outside of your house (e.g. grid) and hurt someone.    Even if you have an inverter with a limiter - it seems to me that the limiter could fail or read things incorrectly or the inverter electronics could fail and somehow.... allow energy out to the grid.  All it takes is 120v 'unexpected shock' and a lineman mishap such as fall off a pole or something.    In addition, even if the equipment works for 1st year... how do you know it will continue to be safe year after year.  

All of which is why it makes perfect sense (to me) to get approvals for grid-tie / approved grid-tie equipment for your situation if you go down the grid-tie approach.
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#22
(10-08-2020, 02:21 PM)OffGridInTheCity Wrote: Not sure yet if this applies in your case - but one of the *key* reasons to avoid unapproved grid-tie is that you could accidentally energize the lines outside of your house (e.g. grid) and hurt someone.    Even if you have an inverter with a limiter - it seems to me that the limiter could fail or read things incorrectly or the inverter electronics could fail and somehow.... allow energy out to the grid.  All it takes is 120v 'unexpected shock' and a lineman mishap such as fall off a pole or something.    In addition, even if the equipment works for 1st year... how do you know it will continue to be safe year after year.  

All of which is why it makes perfect sense (to me) to get approvals for grid-tie / approved grid-tie equipment for your situation if you go down the grid-tie approach.
I get what you're saying, but both the inverters I'm talking about are not suitable for off-grid use, and will not supply power / shut down if no source AC is sensed. I mean - they could be working on the lines during the day, while my solar panels are providing DC power to the inverter. Nothing happens in that case, the inverter just shuts off.

I am from EU west (Netherlands). I'd say somewhere around 30% of homes have solar panels here, none of them are off-grid. (perhaps a few edge-case exceptions, but in general: none)
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#23
(10-08-2020, 02:34 PM)MrAlfabet Wrote:
(10-08-2020, 02:21 PM)OffGridInTheCity Wrote: Not sure yet if this applies in your case - but one of the *key* reasons to avoid unapproved grid-tie is that you could accidentally energize the lines outside of your house (e.g. grid) and hurt someone.    Even if you have an inverter with a limiter - it seems to me that the limiter could fail or read things incorrectly or the inverter electronics could fail and somehow.... allow energy out to the grid.  All it takes is 120v 'unexpected shock' and a lineman mishap such as fall off a pole or something.    In addition, even if the equipment works for 1st year... how do you know it will continue to be safe year after year.  

All of which is why it makes perfect sense (to me) to get approvals for grid-tie / approved grid-tie equipment for your situation if you go down the grid-tie approach.
I get what you're saying, but both the inverters I'm talking about are not suitable for off-grid use, and will not supply power / shut down if no source AC is sensed. I mean - they could be working on the lines during the day, while my solar panels are providing DC power to the inverter. Nothing happens in that case, the inverter just shuts off.

I am from EU west (Netherlands). I'd say somewhere around 30% of homes have solar panels here, none of them are off-grid. (perhaps a few edge-case exceptions, but in general: none)
Good point about the hardware island feature.
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#24
(10-08-2020, 02:40 PM)OffGridInTheCity Wrote:
(10-08-2020, 02:34 PM)MrAlfabet Wrote:
(10-08-2020, 02:21 PM)OffGridInTheCity Wrote: Not sure yet if this applies in your case - but one of the *key* reasons to avoid unapproved grid-tie is that you could accidentally energize the lines outside of your house (e.g. grid) and hurt someone.    Even if you have an inverter with a limiter - it seems to me that the limiter could fail or read things incorrectly or the inverter electronics could fail and somehow.... allow energy out to the grid.  All it takes is 120v 'unexpected shock' and a lineman mishap such as fall off a pole or something.    In addition, even if the equipment works for 1st year... how do you know it will continue to be safe year after year.  

All of which is why it makes perfect sense (to me) to get approvals for grid-tie / approved grid-tie equipment for your situation if you go down the grid-tie approach.
I get what you're saying, but both the inverters I'm talking about are not suitable for off-grid use, and will not supply power / shut down if no source AC is sensed. I mean - they could be working on the lines during the day, while my solar panels are providing DC power to the inverter. Nothing happens in that case, the inverter just shuts off.

I am from EU west (Netherlands). I'd say somewhere around 30% of homes have solar panels here, none of them are off-grid. (perhaps a few edge-case exceptions, but in general: none)
Good point about the hardware island feature.
I'm new to this, could you elaborate on what I described that you called the 'hardware island feature'? What exactly is meant by that?
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#25
>I'm new to this, could you elaborate on what I described that you called the 'hardware island feature'? What exactly is meant by that?
 I could be mis-stating the name of the feature but what I'm trying to express is the idea is that a grid-tie inverter has a safety feature that will not allow it to create power unless voltage already exists on the circuit.   So in theory, when the power company shuts off your power, your grid-tie inverter will no longer operate.   This of course defeats the point of solar power when the grid is down and why people prefer hybrid and off-grid.   

There are cheaper grid-ties like this - https://www.amazon.com/Inverter-Limiter-...360&sr=8-6 - that let you feed excess battery power into your home circuit.  These can have a limiter that monitor the mains coming in to the home (or the circuit it's tied into) and will throttle output so that you don't risk sending power back to the grid.    I guess these have a hardware island feature but this can be defeated by supplying power to the circuit its plugged into from a generator or off-grid inverter.  Or if you plug this into a grid circuit thinking its an off-grid only circuit - again there is risk.

Didn't mean to highjack your thread - its just that I've come to have a heightened respect for DIY grid-tie risks and wanted to raise that IF it applies in your case.   I'm not saying it does Smile

Mine system is off-grid and I use ATSs to consume power in cooperation with the grid (e.g. UL listed mechanical relays ensure the separation between my power and grid power) so I find this thread very interesting / instructive since its something I've not done Smile
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#26
Then its ok for most People but not all are allowed to
* Tie in a battery
* Use any grid tie capable inverter.

So if you want to be legal you need to crosscheck that.

Btw of you send back to grid during Night be prepare that they Will think you tampered with the meter Smile happened to me and others where they didnt Read Up on that we have a battery.
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#27
(10-08-2020, 10:41 AM)MrAlfabet Wrote: I'm sorry for not being more clear.
Right now I have solar panels with a solar inverter that feeds back into the grid all the power that is not used in the home. I'd like to store the excess energy, since I pay more for what I draw from the grid than I get for what I feed back into the grid.
Since I have 3 phase, it is very possible that I'm pulling power from 1 leg, wile the battery is feeding it back to the grid on another leg to keep the total at 0. Also since I'm doing this DIY, it might be possible that I or the algorithm I'm working on will fuck up and actually feed power back to the grid (on total over 3 legs).
I'll give my power company a call to see what's allowed.
Maybe I've misread something, but the inverter link I posted is meant to keep the home energy meter at 0 (for 1 leg though). Could you explain to me how this is not 'feeding back into the grid'? I understand the intention is that the inverter output is always equal to (or lower than) the power usage in the home (on that leg), but if I'm controlling this manually, set it to 2000W, and only use 100W, am I not feeding back into the grid?


It seems like you already have an existing grid-tied system connected to your house and to your electric company. So what you're looking for is an ac-coupled system, which means you're charging off the ac into the battery, then exporting from the battery to the grid when needed. This system is not off grid and will not work during a power outage since as a safety all these units that grid-tie will have anti-islanding to prevent backfeeding (It is possible to use these unit during an outage but it would need a completely different wiring to make it safe.) These ac-coupled systems do not need a solar pv system as it can be used by charging the batteries from the grid when the power is cheap in the middle of the night when it is off-peak and then discharged when the rate is high during the peak times. Great when you have a Time Of Use (TOU) electric rates.

Now it seems you're looking for something diy or cheap so the cheapest would be to get a hybrid system from Mppsolar. This would allow you to charge from ac to battery and then discharge from battery to grid. You seem to be computer savvy so through some programming you should be able to communicate with your power meter and the hybrid inverter to control the export amount and charge amount. You don't have to be exact to reduce it down to zero since you're already set up for exporting so if you export a little more than your actual usage it's not a big deal. I'm not sure but daromer has this set up with a SDM60 and a MPP hybrid I believe. Also it will be up to your utility company if feeding back on one leg is ok. I think it will be fine as long as the imbalance isn't that bad and your neighbors would balance out so it will be negligible.
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#28
(10-08-2020, 06:12 PM)not2bme Wrote: It seems like you already have an existing grid-tied system connected to your house and to your electric company. So what you're looking for is an ac-coupled system, which means you're charging off the ac into the battery, then exporting from the battery to the grid when needed. This system is not off grid and will not work during a power outage since as a safety all these units that grid-tie will have anti-islanding to prevent backfeeding (It is possible to use these unit during an outage but it would need a completely different wiring to make it safe.) These ac-coupled systems do not need a solar pv system as it can be used by charging the batteries from the grid when the power is cheap in the middle of the night when it is off-peak and then discharged when the rate is high during the peak times. Great when you have a Time Of Use (TOU) electric rates.

Now it seems you're looking for something diy or cheap so the cheapest would be to get a hybrid system from Mppsolar. This would allow you to charge from ac to battery and then discharge from battery to grid. You seem to be computer savvy so through some programming you should be able to communicate with your power meter and the hybrid inverter to control the export amount and charge amount. You don't have to be exact to reduce it down to zero since you're already set up for exporting so if you export a little more than your actual usage it's not a big deal. I'm not sure but daromer has this set up with a SDM60 and a MPP hybrid I believe. Also it will be up to your utility company if feeding back on one leg is ok. I think it will be fine as long as the imbalance isn't that bad and your neighbors would balance out so it will be negligible.
Your description is spot on. Power outage is non-existant here (once in a blue moon if they're working on the grid, I'm fine with that as I have the internet and my servers on a few UPS).

If I'm understanding you correctly you're saying buy a hybrid inverter, and simply don't connect the solar panels. Or are you telling me to replace my existing inverter with a hybrid one?
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#29
I am utilizing a single MPPSolar LV5048, which has two charge controllers, to solar charge a battery of Leaf modules, and directly power critical circuits, but then using two GTiL inverters for the rest of the circuits. (obtained from here specifically: https://www.eco-worthy.com/collections/g...0444423220 )

I ended up ignoring my municipality as they would basically only okay off-the-shelf systems installed by professional contractors and only allow pure grid-tie solar. When looking to get all equipment UL approved with a full system stamped by an engineer, and even if I self-installed but monitored by a Master Electrician who knows solar, the cost isn't that far off just getting a solar company to do it. I would venture a guess that 95% of the GTiL users are in municipalities for which their use is technically illegal just as 95% of the users in this forum who attach a self-rolled battery to their house.

I will say I did everything to NEC to the best of my knowledge, but with "self-listed" Chinese/Taiwanese component.
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#30
(10-08-2020, 06:16 PM)MrAlfabet Wrote: If I'm understanding you correctly you're saying buy a hybrid inverter, and simply don't connect the solar panels. Or are you telling me to replace my existing inverter with a hybrid one?


Yes, keep your existing grid-tie inverter and solar panels as it is. It will export to the grid as normal. Then on the hybrid, don't use the solar mppt controller side of it. Just use the ac charger side to zap all that energy that otherwise would have been exported into the battery instead. And then export out of the hybrid when you detect that you're consuming from the grid, like at night for example.
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