Generic advice for household with heavy aircon use?

[jbernal]

Greetings. New to the forum. Not new to offgrid solar but new to the "new" generation of offgrid solar stuff. It has changed a lot since I used it for living on a boat.

Anyways I am building a new house and since we are in central Florida we have both an abundance of sunshine and heat. I will need to run the air conditioner most of the day, for most of the year. Fortunately the house is super well insulated so HOPEFULLY it will not need heavy AC at night, but I want to build a system that has adequate juice storage to run it for a bit in the dark if necessary, and enough juice coming in to fill that back up during the day. I imagine if we overdo the solar input, it will more than cover my needs for daytime cooling.

I have my eye on the Growatt 12kw inverter, seems like it will do what I need it to do but what I am having trouble understanding is how the charge controller works. Is it 120A total end of story? Or is it capable of having more pushed at it and then it can only charge the bank with 120A worth of juice? For example can I run all of my lights and appliances at full blast with, say, 20kw of solar flowing in and it draws its max 120A worth of battery charging current from the surplus? Or if you exceed 120A worth of input it will just turn into a fireworks show?

 

[FilterGuy]

I have not worked with growatt so I can not speak from experience, but I just looked up the manual and found this.



In general, an SCC is rated at it's total output current and I am pretty sure that is the case for Growatt. That means that you can get 120A out of the built in charge controller and that is it. If the inverter is sucking up 120A, then nothing is going to the battery. If the inverter is sucking 60 amp, then 60A is going to the battery.

As a sanity check, I multiplied the system voltage by the 200A to check against the 7000W number and got interesting results.

• If the battery is nearly empty, it will be running around 48V.
  48V x 120A = 5760W
  
  
• If the battery is absolutely full it will be running around 58.4V
  58.4V x 120A = 7008W

So, as expected, 120A is the most current that will come out of the charge controller. However, be aware that when the batteries are low and you need charging the most, you will max out at 5760W.

Or if you exceed 120A worth of input it will just turn into a fireworks show?

As long as you don't exceed the 250V input on the PV input, you can probably put as many panels as you want and there won't be a fireworks show. However, once the SCC is driving 120A, any additional solar production will go unused. In fact some people purposely put more panels on than the SCC will use but arange the panels to keep it below the max voltage. They do this for several reasons:
1) If the panels don't run at full spec (this is typical), it will still max out the SCC.
2) In the morning and late afternoon, they still to get max production even though the sun is at a less than optimum position
3) On cloudy days they get better production.

Finally, I can not tell from the manual if the unit has two PV inputs but only one SCC or if it has two separate 60A SCCs. You should try to confirm whether there is one or two SCCs. If there is only one SCC then the two inputs are wired in parallel and that means you need to put the same panel configuration on both inputs.

 

[jbernal]

OK thanks, this is very helpful. Exactly what I needed to know.

 

[SignatureSolarUS]

Greetings. New to the forum. Not new to offgrid solar but new to the "new" generation of offgrid solar stuff. It has changed a lot since I used it for living on a boat.

Anyways I am building a new house and since we are in central Florida we have both an abundance of sunshine and heat. I will need to run the air conditioner most of the day, for most of the year. Fortunately the house is super well insulated so HOPEFULLY it will not need heavy AC at night, but I want to build a system that has adequate juice storage to run it for a bit in the dark if necessary, and enough juice coming in to fill that back up during the day. I imagine if we overdo the solar input, it will more than cover my needs for daytime cooling.

I have my eye on the Growatt 12kw inverter, seems like it will do what I need it to do but what I am having trouble understanding is how the charge controller works. Is it 120A total end of story? Or is it capable of having more pushed at it and then it can only charge the bank with 120A worth of juice? For example can I run all of my lights and appliances at full blast with, say, 20kw of solar flowing in and it draws its max 120A worth of battery charging current from the surplus? Or if you exceed 120A worth of input it will just turn into a fireworks show?

You can add as many external chargers as needed in the future. we would say that a 5000ES and transformer system has a higher charge controller-to-inverter ratio and the 450V input range eliminates the combiner box.