Solar + Grid Power to a Charge Controller

inelastic · September 2013

I need to install a solar system.

I need to know if I connect solar power + grid power to the charge controller, how is the charge controller going to manage the charging?

I mean will it give priority to solar power first and when solar power is not available due to shade, it will start charging batteries using grid?
Someone told me that considering I have a 50 amps charge contr, 25 amps will be taken from solar while rest 25amp from grid?

I want to get the morningstar tristar MPPT 60 amps model.

Cariboocoot · September 2013

Re: Solar + Grid Power to a Charge Controller

Whoa.

Grid power does not go to the solar charge controller.
Charging from the grid (or a generator) is done via a battery charger, either stand-alone or built-in to the inverter.
As such it is only used when there is inadequate power from the solar array to provide charging. The two charging sources "meet" at the battery and, both being regulated, will work together without problem most of the time. The exception to this is if they are both active at full power sometime, in which case it is possible to supply the combined current of the two and that may be more than the batteries should be subjected to.

inelastic · September 2013

Re: Solar + Grid Power to a Charge Controller

Cariboocoot wrote: »

Whoa.

Grid power does not go to the solar charge controller.
Charging from the grid (or a generator) is done via a battery charger, either stand-alone or built-in to the inverter.
As such it is only used when there is inadequate power from the solar array to provide charging. The two charging sources "meet" at the battery and, both being regulated, will work together without problem most of the time. The exception to this is if they are both active at full power sometime, in which case it is possible to supply the combined current of the two and that may be more than the batteries should be subjected to.

Is there any DC priority in such a setup?

I am asking this because if we don't have DC priority for supplying electricity to our loads(home) and also for charging batteries, we will not be able to maximize our solar savings as grid is also working at the same time.

Is there any way we can have DC priority and grid only comes into play when there is shade/cloudy/night.

Cariboocoot · September 2013

Re: Solar + Grid Power to a Charge Controller

With a properly designed system there is no need to have any such "DC priority".

Do you have loads that are specifically Direct Current?

It is quite normal to have the batteries charge from solar while at the same time supplying power to run loads such as an inverter. Most of us who have off-grid systems do not shut anything down during the day; the panels are size sufficiently to provide charging and handle the typical load demands.

I think you are looking for a system that runs off-grid most of the time, but will have utility power available if needed. No doubt the idea here is to reduce the electric bill and/or make up for unreliable grid power? This is not impossible to do, although it is somewhat more complex. The simplest method is to manually connect the utility power when needed using a transfer switch. Depending on what components are chosen this can be a circuit breaker which when on connects the utility AC to the battery charger circuit or a more complex switch that will connect the AC household loads to the grid as well. From there it can go up to a very sophisticated system which will make the change automatically depending on the battery Voltage - and even time of day if desired.

inelastic · September 2013

Re: Solar + Grid Power to a Charge Controller

Cariboocoot wrote: »

With a properly designed system there is no need to have any such "DC priority".

Do you have loads that are specifically Direct Current?

It is quite normal to have the batteries charge from solar while at the same time supplying power to run loads such as an inverter. Most of us who have off-grid systems do not shut anything down during the day; the panels are size sufficiently to provide charging and handle the typical load demands.

I think you are looking for a system that runs off-grid most of the time, but will have utility power available if needed. No doubt the idea here is to reduce the electric bill and/or make up for unreliable grid power? This is not impossible to do, although it is somewhat more complex. The simplest method is to manually connect the utility power when needed using a transfer switch. Depending on what components are chosen this can be a circuit breaker which when on connects the utility AC to the battery charger circuit or a more complex switch that will connect the AC household loads to the grid as well. From there it can go up to a very sophisticated system which will make the change automatically depending on the battery Voltage - and even time of day if desired.

No brother i have no such loads which work on DC.

I think you didn't fully understand my scenario, maybe I failed to explain.

Now the thing is that if I install the solar panels. I would be going this way:-

Solar panels>chrg contr>batteries>inverter. This is an off-grid system.

However, since i have few batteries, the solar charge will not work at night. So i want my grid to provide electricity through the inverter at night or when there is cloudy/shade.

I know a case where I would have to manually switch on the breaker whenever there is no solar energy. But is there a case where it can automatically switch over to grid when there is shade?

I know of one such hybrid inverter which does all the function automatically. What it does is that it has DC priority so it always gives preference to DC power(i.e from solar), but If the DC power is slightly less than its capacity it takes the remaining power from grid.
Also it automatically switches to grid power when there are clouds or night.

Now can this function be used in a normal inverter or is there any charge controller in the market which such a feature?

inetdog · September 2013

Re: Solar + Grid Power to a Charge Controller

inelastic wrote: »

I know of one such hybrid inverter which does all the function automatically. What it does is that it has DC priority so it always gives preference to DC power(i.e from solar), but If the DC power is slightly less than its capacity it takes the remaining power from grid.
Also it automatically switches to grid power when there are clouds or night.

Now can this function be used in a normal inverter or is there any charge controller in the market which such a feature?

You seem to be mixing up the functions that the CC and the inverter/charger are able to perform.
Normally the CC will get its power only from the panels and will always send as much power as possible directly to the batteries. That is its job, and if it is designed specifically to work together with the same brand's inverter/charger, it can tell the I/C whether the I/C needs to be charging the battery or not.

The I/C on the other hand will be able to either charge the battery from the grid while also letting grid power through to the load (no inverter action at all) or stop trying to charge from the grid and disconnect the grid input in favor of the batteries. That function belongs to the I/C, regardless of what kind of solar CC you add to the system. Basically, the I/C will stop using battery power when the load is too large or when the battery voltage goes too low.
Some I/Cs also have a grid-tied function in which they will sell back power into the grid as long as the battery voltage is high enough (usually about Float level.)

Some I/Cs also have a function called generator support, in which you program the I/C to supply the whole load until one of the two conditions above require it to start a generator, and then it lets the generator share the load with the inverter. A variation on this is grid support, where it will do what you describe and use the inverter until such time that additional power is needed from the grid.

But for all of this, you need to carefully calculate what your cost per kWh is for "free" solar power (mostly initial cost plus regular battery replacement) and compare it to the cost to buy the same kWh from POCO. 95% of the time the POCO power will be cheaper, making your DC priority actually more expensive.
Most people who have grid power available and choose to have a hybrid system, with batteries, are doing that because they have frequent long power outages. In which case they will run on DC at night too because the grid is not there at all. :-)

Blackcherry04 · September 2013

Re: Solar + Grid Power to a Charge Controller

inelastic wrote: »

I know of one such hybrid inverter which does all the function automatically. What it does is that it has DC priority so it always gives preference to DC power(i.e from solar), but If the DC power is slightly less than its capacity it takes the remaining power from grid.
Also it automatically switches to grid power when there are clouds or night.

Now can this function be used in a normal inverter or is there any charge controller in the market which such a feature?

I'd just put a " Low Active Voltage " switch on a Stand Alone Charger. You set the voltage you want it to cut in and out at. This switch has a 3 second delay ( longer would be better ) , that would take more of the chatter out. I'd use a Power Supply type charger like a IOTA that wouldn't try to outsmart it's self.

This switch wouldn't care if it was sunny, cloudy, day or night. It would keep you battery voltage within a range you choose. I use this switch like a fail safe on a expensive set's of Batteries on unattended boats, if the Inverter / Charger goes down with some little glitch you don't lose $5,000.

http://www.solar-electric.com/volconswit.html

Everyday there are new features coming to market. Outback uses the " Re-float" voltage to let their charger use " Grid Power " for charging when available. I am sure you could trick a AGS system into doing different things. The problem is that most Inverter / Chargers make a transfer once qualified AC power is available and loads become pass through, controlling the charger is a secondary issue. There have been Inverter / Chargers that had separate Charger inputs over the years. A hybrid inverter is set up to Grid priority as stand by power and what you want is the reverse where you have Off Grid priority, I don't know if thats out there yet.
..

kenputer · September 2013

Re: Solar + Grid Power to a Charge Controller

have a look at he NV-Q1250 it is a transfer controller that runs load from your inverter but when the batteries get low it switches to grid power til your batteries are recharged.
http://www.novanewenergy.com/ProductShow.asp?ID=45

YehoshuaAgapao · September 2013

Re: Solar + Grid Power to a Charge Controller

inelastic wrote: »

No brother i have no such loads which work on DC.

Solar panels>chrg contr>batteries>inverter. This is an off-grid system.

Bi-modal solar systems with DC-coupled battery banks are wired as if it were an off-grid system. The single battery-based inverter does everything. Outback Radian, Outback GFX/GVFX, Xantrex XW are DC-coupled bi-modal inverters.

AC-coupled Bi-modal systems have a grid-tie inverter backfeeding the subpanel and the battery based inverter's AC-out port. AC-coupled systems need at least two inverters. AC-coupled bi-modal systems are wired on the PV side as if it were a grid-tie system. Magnum inverters are typically used in these, but Xantrex XW and Outback Radian also support AC coupling / backfeeding of the AC-out port.

Outback Radian and Xantrex XW also have built-in automatic transfer switch for a generator in addition to its grid connection though the ATS only services the subpanel. Outback Radian supports mini-grid - stay off-grid as much as possible, using the grid in place of the generator if available if the batteries get too low. Xantrex XW will not voluntarily disconnect from the grid if it has a valid grid connection.

andersondiaz · October 2013

Re: Solar + Grid Power to a Charge Controller

hello, my name is Anderson from Dominican Republic

in a few months i'll installing about 10 solar panels with micro inverter

and want to know if, is possible to do (bi-modal (Grid-tie w/battery)) this with micro inverter?

Tks

bill von novak · October 2013

Re: Solar + Grid Power to a Charge Controller

andersondiaz wrote: »

and want to know if, is possible to do (bi-modal (Grid-tie w/battery)) this with micro inverter?

Yes but it's complex and there are only a few inverters that allow you to do this. You will need the grid tie inverters along with a battery backed iinverter like the Outback series. It will generally be cheaper to just get a battery backed grid tie inverter.

What is your goal? Completely independent operation? Backup for occasional outages?

andersondiaz · October 2013

Re: Solar + Grid Power to a Charge Controller

bill von novak wrote: »

Yes but it's complex and there are only a few inverters that allow you to do this. You will need the grid tie inverters along with a battery backed iinverter like the Outback series. It will generally be cheaper to just get a battery backed grid tie inverter.

What is your goal? Completely independent operation? Backup for occasional outages?

is for occasional outges, I do not need a large bank of batteries.
only use 4 batteries (225a).

but I mean a system with microinverters

Blackcherry04 · October 2013

Re: Solar + Grid Power to a Charge Controller

andersondiaz wrote: »

is for occasional outges, I do not need a large bank of batteries.
only use 4 batteries (225a).

but I mean a system with microinverters

Micro Inverters do not work without Grid or a reference voltage. If you need a small backup, get a small generator. Anything with Solar is expensive and won't supply you any amount of power but for a very short time.

ggunn · October 2013

Re: Solar + Grid Power to a Charge Controller

andersondiaz wrote: »

is for occasional outges, I do not need a large bank of batteries.
only use 4 batteries (225a).

but I mean a system with microinverters

IMO you should take a hard look at how crucial it is for your solar power system to continue to function during a grid outage. Building that functionality into your system greatly increases its complexity and cost. If your outages are only occasional and of short duration, it may be better to just get a generator to get through the outages and let the PV go off line. Grid tied PV is a strategic tool and grid outages require a tactical solution.

bill von novak · October 2013

Re: Solar + Grid Power to a Charge Controller

andersondiaz wrote: »

is for occasional outges, I do not need a large bank of batteries. only use 4 batteries (225a). but I mean a system with microinverters

1) If you want a system with microinverters and you want battery backup, then you need microinverters AND a larger battery based inverter. You can't just use the microinverters. You need both.

2) If it's just for occasional outages then just go with the microinverters and use either a cheap UPS ($200) or a generator ($1000) for backup.

3) If you want SOLAR backup, but don't want two sets of inverters, then ditch the microinverters and get an SMA inverter with something called a "secure power supply." It will give you some power when the grid goes out.

andersondiaz · October 2013

Re: Solar + Grid Power to a Charge Controller

bill von novak wrote: »

1) If you want a system with microinverters and you want battery backup, then you need microinverters AND a larger battery based inverter. You can't just use the microinverters. You need both.

2) If it's just for occasional outages then just go with the microinverters and use either a cheap UPS ($200) or a generator ($1000) for backup.

I can install a large inverter 1.5kw to 2 kW, is the solution i seek.

can you give me examples of the components I need to buy for option 1 and 2, you mention?

i can use one of this? http://www.ebay.com/itm/APC-SMART-UPS-RT-5000VA-3500W-208V-SURTD5000XLT-Tested-with-New-Batteries-/221210046324?pt=US_Uninterruptible_Power_Supplies&hash=item3381256f74

tks

YehoshuaAgapao · October 2013

Re: Solar + Grid Power to a Charge Controller

andersondiaz wrote: »

hello, my name is Anderson from Dominican Republic

in a few months i'll installing about 10 solar panels with micro inverter

and want to know if, is possible to do (bi-modal (Grid-tie w/battery)) this with micro inverter?

Tks

You can have battery bank with microinverters with a AC-coupling only. The microinverters backfeed the battery-based inverter via the subpanel. Magnum (don't remember model), Xantrex XW, and Outback radian support AC coupling. There might be others.

YehoshuaAgapao · October 2013

Re: Solar + Grid Power to a Charge Controller

Do keep in mind that most battery based inverters that support AC coupling (AC backfeed from a grid-tie inverter or microinverters) are 48V on the DC input (battery bank). If the Xantrex XW4024 supports AC coupling, this one is 24V.

zoneblue · October 2013

Re: Solar + Grid Power to a Charge Controller

The down side to ac coupling is the cost. Partly because you need two inverters, but partly becasue the particular inverters that support ac coupling as just expensive to start with. Ac coupling works best in large sprawly installations with muliple arrays spreadout over any distance.

Id be thinking about using one or more UPS for critical appliances. Or building something like it from a mains charger, batterys and what not.

Lastly there are some really new grid tie inverters that have 'emergency' modes, which allow themselves to island safely.

Solar + Grid Power to a Charge Controller

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