Sunny Island doubts

fca1

Hi there, i'm looking for a device that can do all of this:


-Can manage several energy sources (solar+grid+genset)
- Have a battery bank and charge the batteries
- Functions as inverter when running from batteries

i was looking at the SMA sunyisland but i'm confused because on all diagrams that it needs a external charge controller or or the pvs are connected by ac with a sunnyboy..
it's correct ? the sunnyinsland don't have a mppt charger ?

any device on the market that do this ??

thanks

stephendv

Re: Sunny Island doubts

No, the sunny island does not have an mppt charger built in. You either have to use an external charge controller, or a sunny boy to connect solar panels.

Almost every inverter/charger on the market can do what you're looking for EXCEPT take solar as input. In other words, if you use an external solar charge controller then you can choose between a wide variety of inverter/chargers that will manage grid/generator/batteries and inverting. In the US market some popular choices are: Xantrex, Magnum, outback and SMA sunny island. In the EU market: SMA, Xantrex, outback, Victron, studer.

But if you specifically want an all-in-one device then you could look at the Nedap powerrouter: http://powerrouter.com/

Cariboocoot

Re: Sunny Island doubts

There are "all in one" charge controllers + inverter chargers. Several have come up in the forum from time to time. All seem to be overseas. None seem to be particularly good; too many specification compromises. I would avoid them.

The majority of system use separate charge controllers for solar input just as stephendv said. They work better and are more flexible in design. Some will communicate between controller and inverter others won't; it is not critical that they do so, but it helps in some applications.

BB.

Re: Sunny Island doubts

One additional possibility--Your generator/grid connection.

There are "Hybrid" AC Inverters that can do off grid power (run loads from battery bank and manage a genset with manual or auto start, etc.)--And if you have AC grid, it can feed back excess charging power from the DC Battery bank back to the AC grid (reduce your power bill when the grid is up and running).

That is about the only "big difference" between a off grid inverter (or inverter+charger) and a Hybrid (the ability to feed AC power back into the power lines).

There are a few off grid inverters these days that are capable of being connected to a Grid Tied AC Inverter (source+GTI and no battery bank). The GT inverter can "back feed" the OG inverter and recharge the battery bank (or share AC loads too, with the local grid frequency/voltage being "set" by the Off Grid inverter). And there is some sort of battery charge control needed (dump load on battery, or some method to modulate/knock off line the GT inverter when the battery bank is full).

The SMA Sunny Island is probably the best "local AC grid" system out there. Appears to be well thought out and supports "modulating" the GT inverter (by varying the Off Grid AC inverter's frequency a small amount) instead of needing a dump load or to knock off the GT inverter when battery is full (called "Bang/Bang" control theory--Unit is 100% on until it is turned 0% off).

In the US, the SMA sunny island units are pretty expensive. In Europe--They should be much more competitive.

In the US, our "Hybrid" inverters are "cost effective enough" that some Mfg. (like Xantrex/Schneider) can sell the "Hybrid" inverter into both on grid and off grid installations. The ability to Grid Tie Connect to the AC utility does not add much to the hardware costs.

What are your loads (watts, watt*hours/kWH per day) are you looking at.

Are you off grid or On Grid with unreliable power? Are you in the UK, or was it on a small island like Malta (sorry, I get poster information mixed up sometimes).

Solar panels + charge controller should be designed to manage 100% of their rated power for years on end. Solar Panels are perfectly OK to series control (PWM or MPPT type charge controllers, or feeding a GT inverter)--Good quality panels should not be damaged if running at 100% load all day long, or if they are turned off at noon (battery full, utility grid down).

Standard "Horizontal Axis" Wind Turbines, on the other hand, usually need 100% loading when the wind is blowing. Even in moderate winds, the turbine will over-speed to destruction if not electrically loaded (or braked, or furled, or feathered, or blades stalled, etc.). So a shunt type (dump) charge controller and load is needed to keep the battery bank from over charging.

-Bill

ggunn

Re: Sunny Island doubts

fca1 wrote: »

Hi there, i'm looking for a device that can do all of this:


-Can manage several energy sources (solar+grid+genset)
- Have a battery bank and charge the batteries
- Functions as inverter when running from batteries

i was looking at the SMA sunyisland but i'm confused because on all diagrams that it needs a external charge controller or or the pvs are connected by ac with a sunnyboy..
it's correct ? the sunnyinsland don't have a mppt charger ?

Correct; the Sunny Island inverts from batteries and you must have either another inverter or a charge controller to interface with PV. The principle reason for that is that the DC voltages from PV and from batteries are typically very different.

fca1

Re: Sunny Island doubts

Hi
i have grid but want to go to off-grid............. (i'm not after a financial case

I now have solar panels 4.7KW + mppt charge controller (tristar mppt60 + midinite150) + batteries and studer xpc inverter and a dyi switch that activate the acin to the studer when batteries are low (reaches 23.5v).
I wanted a more integrated device (inverter+charge controller) so that can measure a real SOC on batts and make decisions on when to shift based on parameters like soc, time of day etc...

this device should have acin for grid and ac in for gen...
thanks

Cariboocoot

Re: Sunny Island doubts

You are looking at the need for a battery monitor to measure SOC of the batteries "on the fly" and make system adjustments accordingly.

I'm not clear on exactly what you are trying to do with the information, though. If you plan on going off grid but still have the grid available if the batteries get too low, then it is possible to set up a system where the grid acts as a generator and will be connected to AC IN if the battery Voltage falls too low. It is simply a matter of having an automatic generator start system adapted to control a relay that switches (and can handle) the grid power to AC IN instead of actually starting a generator. A top-of-the-line (expensive) inverter-charger will have gen start parameters that can include time of day, day of week, et cetera to avoid connecting it when solar will do the job.

The solar charge controller really does not have to be integral for this to operate.

stephendv

Re: Sunny Island doubts

fca1 wrote: »

studer xpc inverter and a dyi switch that activate the acin to the studer when batteries are low (reaches 23.5v).
I wanted a more integrated device (inverter+charge controller) so that can measure a real SOC on batts and make decisions on when to shift based on parameters like soc, time of day etc...

The studer XPC already has an integrated transfer switch and it sounds like it will automatically make decisiones about when to charge from the grid and when to invert from batteries. You just need to configure it From their website: http://www.studer-inno.com/?cat=sine_wave_inverter-chargers&id=433&tab=3

The 16 A. potential free contact can be programmed according to the user wishes. It reacts according to the battery levels, as well as to the system status (alarm conditions, public grid, presence, sunlight’s presence…), and provides:
1/ Automatic disconnection of second priority users (conditional supply).
2/ Alarm signalization, acoustic signal, MODEM, radio alarm etc.
3/ Conditional battery charge.

The limitations are that the decision to charge the batteries from grid will be based on the voltage, not on the SoC, because it doesn't have a built in SoC meter. As far as I know it won't do time of day grid connection either. From what I've heard, the studers are great inverters but are not the easiest to configure...

If you wanted to switch to the Sunny Island, you could get their 2kW unit which includes a built in SoC meter and all decisions about charging and connecting to the grid is based on SoC not on battery voltage. It also has some options for programming time of day connection to the grid, but it's not overly flexible. You can find their manuals on the SMA site which will describe it in more detail.

There are very few inverter/chargers that have both an AC in for grid and a separate AC in for generator. SMA expects you to install an external transfer switch to connect those two sources to its single AC input.

BB.

Re: Sunny Island doubts

In the end, for most people in the "first world", AC utility power is cheaper than battery backed solar power. Batteries also age with cycling (less life, most costs)--So, typically people look at these as "USP" systems (uninterruptable power supply).

If your utility supports "Net Metering" with solar RE systems (feed power from solar system back to the grid--i.e., spins your utility meter backwards), then you have the option of "pure" grid tied inverters (no battery bank) or "hybrid" inverters (with battery bank for backup power during utility failures).

In my region, we have very reliable (but not cheap) utility power. So a pure GT inverter+solar panels with a back up generator is a much better deal.

For people with extended outages (weeks to month+) a hybrid solar power system may be the optimum solution (or pure off grid system that uses solar+generator+utility power when available) for power.

There is another group of people that want solar power and have utility power. And their utilities do not allow "net metering" (direct connection of GT inverter and back feeding utility) is not legal. They want a "hybrid" system that uses as little utility power as possible, and does not back feed. Some systems come close, but there is nothing out there today that will do exactly that (Xantrex XW is one that comes close, but still has a few hundred watt "leak" from utility). These type of systems require a fair amount of setup/programming by the end installer/user to get them working as desired.

Another issue that we have seen here in Europe and starting to see in California are utilities that are "freaking out" over Net Meter GT systems with "hybrid inverters (and battery banks). The concern is that people are "illegally" buying cheap power at night and selling it back during the day.

I don't believe that is a huge issue/problems (in fact, just to time shift power would cost on the order of $0.45 per kWH to buy $0.09 per kWH at night and sell it at $0.30 per kWH during the day with my utility/power levels).... Does not even make economic sense (equipment+batteries+maintenance makes it an over all loss of money).

-Bill

fca1

Re: Sunny Island doubts

BB. wrote: »

There is another group of people that want solar power and have utility power. And their utilities do not allow "net metering" (direct connection of GT inverter and back feeding utility) is not legal. They want a "hybrid" system that uses as little utility power as possible, and does not back feed. Some systems come close, but there is nothing out there today that will do exactly that (Xantrex XW is one that comes close, but still has a few hundred watt "leak" from utility). These type of systems require a fair amount of setup/programming by the end installer/user to get them working as desired.

-Bill

Hi, I fit in this group ... But my ultimate goal is to remove the Grid completely.... Wishes.....

I will have a look at these xantrex xw

mtdoc

Re: Sunny Island doubts

BB. wrote: »

I
There is another group of people that want solar power and have utility power. And their utilities do not allow "net metering" (direct connection of GT inverter and back feeding utility) is not legal. They want a "hybrid" system that uses as little utility power as possible, and does not back feed. Some systems come close, but there is nothing out there today that will do exactly that (Xantrex XW is one that comes close, but still has a few hundred watt "leak" from utility). These type of systems require a fair amount of setup/programming by the end installer/user to get them working as desired.

I believe that many people use the Outback "non G" inverters like the VFX series that way by using HBX mode - though I don't have any personal experience with that. The Outback GVFX inverters can be set up easily to use grid power as needed and not to back feed and I assume the newer Radian's can as well. So lots of ways to do this I think.

NorthGuy

Re: Sunny Island doubts

BB. wrote: »

They want a "hybrid" system that uses as little utility power as possible, and does not back feed. Some systems come close, but there is nothing out there today that will do exactly that (Xantrex XW is one that comes close, but still has a few hundred watt "leak" from utility).

I wouldn't say Xantrax XW comes close to that. 1A leak that it has us 5.7kWh per day. People say it may backfeed to the grid if loads switch fast.

Outback Radian has a mode called MiniGrid, which does exactly that - minimizes grid usage. At least they say so in their documentaton. It's a fairly new product.

mtdoc

Re: Sunny Island doubts

Regarding HBX mode on Outback FX or GVFX inverters, below is from the Outback Mate manual

What it does: HBX Mode allows control over the use of grid-supplied power based on user determined battery voltage and time set points. A user can maximize renewable energy use and minimize the use of grid-supplied power through careful HBX usage.
The OutBack default values* for HBX(24V system) are the following:
• High voltage—26 volts
• Lowvoltage—24 volts
• Time for both high and lowsettings—one hour
When the battery voltage remains at 26 voltsfor one hour,the FXwill disconnectfrom the
grid and the system willrun on battery-supplied power.Ifthe battery voltage fallsto 24 volts
for one hour,the FXconnectsto the grid. During this connected period,the grid-suppliedAC
current will power the loads and recharge the batteries unless the user manually shuts off the
FXcharging function off.With the charger off,the gridwill only powerthe loads, allowing
renewable energy sources to recharge the batteries. This avoids running the loads from the
batteries and repeatedly charging and discharging them using more expensive utility power.

* Double these valuesfor a 48V system; divide them by one half for a 12V system.These
values are not temperature compensated.

HBX Mode:
• Standsfor high battery transfer
• Is used with grid-connected FXSeriesInverter/Chargersthat have utility power as their AC
input
• Is a mode primarily used in applications that have enough renewable energy (RE) power
production to meet the needs of the loads most of the time
• Allows the FX to connect to an AC source if he battery voltage has fallen below a programmable set point for a user configurable amount of time (MATE will then allow the FX to remain connected to the AC source until the battery voltage has risen above a second set
point for a programmable amount of time)
The MATE detects when the battery is truly low and needs charging as opposed to a sudden
and momentary drop caused by a sizable demand for power from a device such as a motor.
At these times,the MATE directs the FX to use AC power until the battery isfully charged
again. The user programs in the amount of time a battery can be below the low voltage and
the amount of time afterit’sfully charged before the MATE startsissuing its commands.The
MATE uses these times to switch back and forth between AC and battery power. Additionally,
inHBX mode,the FXcharging function can be shut off to allowthe alternative energy source
to recharge the batteries while the loads are powered by the utility grid.

stephendv

Re: Sunny Island doubts

As I said before your existing studer xpc inverter is a full off-grid inverter/charger, so you likely don't need to buy anything to get it to work as you want. It also has a multifunction relay built in which can be used to start a generator, so you could use this relay to drive a more powerful contacter to connect and disconnect the grid from AC input. From their manual:

Attachment not found.

fca1

Re: Sunny Island doubts

stephendv wrote: »

As I said before your existing studer xpc inverter is a full off-grid inverter/charger, so you likely don't need to buy anything to get it to work as you want. It also has a multifunction relay built in which can be used to start a generator, so you could use this relay to drive a more powerful contacter to connect and disconnect the grid from AC input.

Hi i don't have the Xpc unit that allow to program it.. But even so it can't do what I want ...
For my readings outback hbx mode does what I need, so when moving for 48v I will go for the outback + mate to program it..

stephendv

Re: Sunny Island doubts

fca1 wrote: »

Hi i don't have the Xpc unit that allow to program it.. But even so it can't do what I want ...
For my readings outback hbx mode does what I need, so when moving for 48v I will go for the outback + mate to program it..

The Victron multiplus inverter/chargers also offer extensive programmability when used with the grid. You'll need to buy the MK2 USB computer interface to program it all though, but it still comes out cheaper than outback + mate. The victron also allows you to program grid connection based on the AC current, e.g. with a 2kW inverter you can program it to connect to the grid if the draw exceeds 1.9kW for 5 minutes. The 2kW victron has a 30A transfer switch, so can allow up to 6.9kVA from the grid to the loads.

Neither the outback nor victron will be able to make decisions based on battery SoC, only battery voltage and AC current. If you want to base the decisions on SoC then you'll need an external battery monitor or the Sunny Island.

fca1

Re: Sunny Island doubts

Hi after some reading I think the victron Quattro 5000 will do almost what I nneed following this guide
http://www.victronenergy.com/upload/documents/White%20paper%20-%20Achieving%20the%20impossible%20-%20rev%2000%20-%20EN.pdf

I see examples like example 2.4 that is what I want but on reverse, I mean I want to have priority on the batts and limit the bat usage based on soc or if no soc possible by voltage but that only when low batt is when I want to use power assist from grid ...

is this possible to configure with the ve software so it behaves like this ? Any1 have this unit?

Maybe I can simulate this by using grid as genie ???

thanks
maybe I will open a topic on victron ..

Eric L

Re: Sunny Island doubts

There is another group of people that want solar power and have utility power. And their utilities do not allow "net metering" (direct connection of GT inverter and back feeding utility) is not legal. They want a "hybrid" system that uses as little utility power as possible, and does not back feed. Some systems come close, but there is nothing out there today that will do exactly that (Xantrex XW is one that comes close, but still has a few hundred watt "leak" from utility). These type of systems require a fair amount of setup/programming by the end installer/user to get them working as desired.

Besides the Outback mentioned above, the Magnum MS-PAE inverters will do this also (you need the ME-ARC50 remote as well to program them). Unlike the Xantrex XW units, they don't leak utility power (i.e., have a constant pull from the utility of about 100 watts, as the XWs apparently do, even when plenty of surplus renewable energy is available), but will power whatever loads are connected to them solely from the batteries, until the battery voltage falls below a user-selected set point. When that happens, the power goes completely to grid power, until the battery voltage goes above another user-selected set-point, when it goes back to batteries/renewables. So it's pretty flexible.

Works very well out of the box and was not difficult to set up for me -- maybe 5 minutes of programming.

gww1

Re: Sunny Island doubts

Mtdoc
The problim with outback, compared to my wish inverter, is that it seems to be all on grid or all on the inverter unless you are using the grid sell. You can not run large loads with both the inverter and the grid supporting them.

This means a dedicated breaker box for the inverter loads, not whole house. It also cycles the batteries "maby" many times in one day rather then letting the batteries get to compleatly full.

If you could relize the grid sell functions and have a stop gate at the grid meter, the system would be cheeper to install, put less stress on the batteries and use all your pv.

I do realize batteries should not float all the time.

I may not understand how things really work though as I have not actually done it yet.

Just my thoughts on what I wan't and what I think I have.

Thanks
gww

Ps I would really like to help run my central air on days I am producing well, without buy different ac.

mtdoc

Re: Sunny Island doubts

gww1 wrote: »

Mtdoc
The problim with outback, compared to my wish inverter, is that it seems to be all on grid or all on the inverter unless you are using the grid sell. You can not run large loads with both the inverter and the grid supporting them.

If I'm understanding you correctly then no - the GVFX will invert to support loads and use the grid to make up the difference if your solar production is not enough to supply the loads.

This means a dedicated breaker box for the inverter loads, not whole house.

True if you are not backing up the whole house with your system.

It also cycles the batteries "maby" many times in one day rather then letting the batteries get to compleatly full.

Not true. The batteries are kept at float or your sell voltage (which should be at or close to the float voltage). The batteries are not cycled unless the grid connection is lost - or unless you choose to cycle them.

I do realize batteries should not float all the time.

I think it depends on the batteries. AGMs do very well kept in float for their lifespan.

Ps I would really like to help run my central air on days I am producing well, without buy different ac.

See above. The GVFX will do this - PV to help run your central air with grid helping if not enough PV to completely power it.

stephendv

Re: Sunny Island doubts

fca1 wrote: »

is this possible to configure with the ve software so it behaves like this ? Any1 have this unit?
Maybe I can simulate this by using grid as genie ???

There isn't much difference between a lot of the inverters. The Sunny Islands, Victron quatro, Victron Multiplus and Studer Xtender all support the same essential features, with only minor differences between them, e.g.:

- The Victron quatro has another AC output which can be used for opportunity loads
- The Victron multi and cuatro must be programmed through a PC so you need to buy an extra "MK2" adapter to program them with VE configure.
- The Sunny Islands have a built in battery meter, so it can make decisions based on SoC not battery voltage. You don't need to buy anything extra to program it.

All of the above inverters will do what you want, the sunny island has the additional advantage of making the decision based on battery SoC.

gww1

Re: Sunny Island doubts

Originally Posted by gww1
Mtdoc
The problim with outback, compared to my wish inverter, is that it seems to be all on grid or all on the inverter unless you are using the grid sell. You can not run large loads with both the inverter and the grid supporting them.

If I'm understanding you correctly then no - the GVFX will invert to support loads and use the grid to make up the difference if your solar production is not enough to supply the loads.

In referance to your answer: by reading the stuff from outback that you posted earlyer it seems that in hbx mode, when the battery is high it will invert the total load untill the battery is low, then it will switch to the grid to run the total load. My understanding (which may be wrong) is that the only way to have your pv and the grid provide power at the same time is when you are in sell mode. When in sell mode if your heavy loads kick off the exess then goes out to the grid, which if no grid tie agreement may get you in trouble.

Thank you for your answer so far.
gww

fca1

Re: Sunny Island doubts

stephendv wrote: »

There isn't much difference between a lot of the inverters. The Sunny Islands, Victron quatro, Victron Multiplus and Studer Xtender all support the same essential features, with only minor differences between them, e.g.:

- The Victron quatro has another AC output which can be used for opportunity loads
- The Victron multi and cuatro must be programmed through a PC so you need to buy an extra "MK2" adapter to program them with VE configure.
- The Sunny Islands have a built in battery meter, so it can make decisions based on SoC not battery voltage. You don't need to buy anything extra to program it.

All of the above inverters will do what you want, the sunny island has the additional advantage of making the decision based on battery SoC.

Stphendv, may be i'm not getting but following the victron example this.

Attachment not found.

Where you limit the ac power to 4amps and then if the loads requires more amps it will get the additional amps from the batts (power assist function victron name)..

What i want is the reverse of this, based on SOC or Bvolt, i mean when until the battery voltage reaches X volts all loads come from the batts then if bvolt reduces below that point will get additional power from the grid...

I just download the victron software (that have a nice demo mode) to see if i can understand if this can be done... i read some where also that the victrons can be connected to victon bmvs and work based on soc also...

but i'm not "seeing " on how to achieve this because most of the inverters are oriented to default to grid as soon as they sense the grid in .

stephendv

Re: Sunny Island doubts

fca1 wrote: »

but i'm not "seeing " on how to achieve this because most of the inverters are oriented to default to grid as soon as they sense the grid in .

Yes, that's the default behaviour but you can configure them to only connect to grid based on battery voltage. I can only speak with certainty about the Sunny Island where you can program it exactly for what you're looking for:

Parameter 232 #08 = GridCharge to charge while on the grid
232 # 41: GdSocEna = enable to enable connecting to the grid based on SoC
233 # 01 through to 09 are all dedicated to controlling grid connection, e.g.:

SOC limit for switching on the grid for time1
SOC limit for switching off the grid for time1
SOC limit for switching on the grid for time2
SOC limit for switching off the grid for time2

So you can program it to connect to grid if SoC is below 50% and it's between 9am and 5pm, or if SoC is below 60% and it's between 5pm and 9am (or whatever suits you).

For the other inverters, I strongly suspect that the victrons also support this and even if they didn't have this specific option you can trick them into working this way because they all support automatic-generator start based on SoC or batt voltage. So you install a power relay between your grid and inverter AC in and you connect the inverter's internal generator signal relay to the power relay. Then you configure the inverter turn the generator on when the battery voltage or SoC dips below X%, so the inverter's internal relay will switch your external power relay and the inverter will think that you've just turned the generator on, when in fact you've just connected the grid. You can also tell it turn the gen off based on voltage or SoC.

vtmaps

Re: Sunny Island doubts

I think the issues being brought up in this thread are similar to those in another fairly recent thread:
http://forum.solar-electric.com/showthread.php?16309

--vtMaps

fca1

Re: Sunny Island doubts

stephendv wrote: »

Yes, that's the default behaviour but you can configure them to only connect to grid based on battery voltage. I can only speak with certainty about the Sunny Island where you can program it exactly for what you're looking for:

Parameter 232 #08 = GridCharge to charge while on the grid
232 # 41: GdSocEna = enable to enable connecting to the grid based on SoC
233 # 01 through to 09 are all dedicated to controlling grid connection, e.g.:

SOC limit for switching on the grid for time1
SOC limit for switching off the grid for time1
SOC limit for switching on the grid for time2
SOC limit for switching off the grid for time2

So you can program it to connect to grid if SoC is below 50% and it's between 9am and 5pm, or if SoC is below 60% and it's between 5pm and 9am (or whatever suits you).

For the other inverters, I strongly suspect that the victrons also support this and even if they didn't have this specific option you can trick them into working this way because they all support automatic-generator start based on SoC or batt voltage. So you install a power relay between your grid and inverter AC in and you connect the inverter's internal generator signal relay to the power relay. Then you configure the inverter turn the generator on when the battery voltage or SoC dips below X%, so the inverter's internal relay will switch your external power relay and the inverter will think that you've just turned the generator on, when in fact you've just connected the grid. You can also tell it turn the gen off based on voltage or SoC.

thanks, but for what i see the victron powerassist is not a simple transfer they can join the inverter and grid to the output...

I already thinking on that part of using the grid as "generator" mode, meaning i will turn it on as need.. but the power assist seems very good if it work in reverse, meaning that when some heavy load get turned on it will get more power from the grid....



Asked for price quote for both sunyisland and victron quattro 5000.



thanks

stephendv

Re: Sunny Island doubts

fca1 wrote: »

I already thinking on that part of using the grid as "generator" mode, meaning i will turn it on as need.. but the power assist seems very good if it work in reverse, meaning that when some heavy load get turned on it will get more power from the grid....

Yes this "power assist" feature is common to all the inverters I listed. You can program them to limit AC in and then they will supply the difference from the battery, the other manufacturers call it "generator boost" or "generator assist". Now I understand what you mean by "reverse", and unfortunately none of them can be configured as you describe, i.e. prioritise battery during high current draw and take the difference from the grid.

Once the connection to the grid is made, then all power will come from the grid up to the preprogrammed current limit. Any excess above this limit will then come from the batteries. But these high current draw events should be fairly infrequent.

Blackcherry04

Re: Sunny Island doubts

stephendv wrote: »

Yes this "power assist" feature is common to all the inverters I listed. You can program them to limit AC in and then they will supply the difference from the battery, the other manufacturers call it "generator boost" or "generator assist". Now I understand what you mean by "reverse", and unfortunately none of them can be configured as you describe, i.e. prioritise battery during high current draw and take the difference from the grid.

Once the connection to the grid is made, then all power will come from the grid up to the preprogrammed current limit. Any excess above this limit will then come from the batteries. But these high current draw events should be fairly infrequent.

Although the Generator Support works, don't count on it being " seamless ". There is enough delay in it to cause issues with A/C and Refrigerator compressors. There will also be a huge load dropped on the fuse for the connected inverter and batteries as the load is being sustained before the transition is complete. If it's on Grid it may be different than the above. My Outback GFX 1312 has no problem popping a 175 amp fuse picking up a 500 watt load, then the compressor will short cycle and overload it on 4/0 cables and 1000 amp battery bank.

mtdoc

Re: Sunny Island doubts

gww1 wrote: »

In referance to your answer: by reading the stuff from outback that you posted earlyer it seems that in hbx mode, when the battery is high it will invert the total load untill the battery is low, then it will switch to the grid to run the total load. My understanding (which may be wrong) is that the only way to have your pv and the grid provide power at the same time is when you are in sell mode. When in sell mode if your heavy loads kick off the exess then goes out to the grid, which if no grid tie agreement may get you in trouble.

Thank you for your answer so far.
gww

I haven't used hbx mode myself, so I can't say for sure. My understanding is that hbx mode is best used when you have enough RE to run all your loads from it- so what you say may be true (i'd ask on the Outback forum or call them). I had mentioned it because it sounded like that might something the OP wanted.

BUT I can say for sure that when in "normal" grid tie mode, the GVFXs can do just what you propose while having "SELL RE" turned off - so no danger of selling to the grid if the PV power exceeds the loads.

Eric L

Re: Sunny Island doubts

What i want is the reverse of this, based on SOC or Bvolt, i mean when until the battery voltage reaches X volts all loads come from the batts then if bvolt reduces below that point will get additional power from the grid...

It sounds like what you have in mind would work like a reverse absorption stage. So in absorption, voltage is held constant while current to the batteries is scaled back as the batteries fill. What you're suggesting would be to hold voltage constant in the face of a load. Since the batteries would be under load, their current would steadily drop off as they drained and the grid would be used to make up the difference needed to hold the voltage. I'm pretty sure nothing does this, including the HBX mode in the Outbacks. Also, this is not the way generator support works as I understand it.

I'm trying to think of a reason why this sort of design would be desirable. I guess it might allow better capacity utilization of an off-grid system design that nonetheless had grid support available but wasn't selling to grid. What it might let you avoid is the situation where a heavy load pulled the voltage so low that the system switched to grid prematurely, while the batteries still had a good charge. But frankly, if this were happening with any regularity, the batteries wouldn't be that well balanced with the loads anyway, and the proper solution would be to reduce the load or increase the battery bank size.

I guess in other words I don't see a good reason to have a grid-supported system work as you describe, as opposed to a straight all-or-nothing supply from the batteries as the Outbacks, Magnums, Sunny Islands, and Victrons already do.

fca1

Re: Sunny Island doubts

Eric L wrote: »

It sounds like what you have in mind would work like a reverse absorption stage. So in absorption, voltage is held constant while current to the batteries is scaled back as the batteries fill. What you're suggesting would be to hold voltage constant in the face of a load. Since the batteries would be under load, their current would steadily drop off as they drained and the grid would be used to make up the difference needed to hold the voltage. I'm pretty sure nothing does this, including the HBX mode in the Outbacks. Also, this is not the way generator support works as I understand it.

I'm trying to think of a reason why this sort of design would be desirable. I guess it might allow better capacity utilization of an off-grid system design that nonetheless had grid support available but wasn't selling to grid. What it might let you avoid is the situation where a heavy load pulled the voltage so low that the system switched to grid prematurely, while the batteries still had a good charge. But frankly, if this were happening with any regularity, the batteries wouldn't be that well balanced with the loads anyway, and the proper solution would be to reduce the load or increase the battery bank size.

I guess in other words I don't see a good reason to have a grid-supported system work as you describe, as opposed to a straight all-or-nothing supply from the batteries as the Outbacks, Magnums, Sunny Islands, and Victrons already do.

I want to use as much as possible the solar power and as I have more solar than batts I want that during the day all the loads are used from solar...
But in the night and in winter and in some heavy loads I need to shift to the grid to protect the batteries from heavy discharge...
And so what I want is until my batts are at 60% soc all come from batts/solar as I have 140amps charge capacity in the day I can use let's say 90amps to charge and the rest to the inverter.... ( this will be dynamic as is today depending on the loads)
So in good days maybe never need the grid, but in bad days of sun or heavy loads or both it will get help from the grid...

So I don't see what you mean with the batt charging voltage and absorption ...
Ps: over here I can't sell to the grid