inverter / charger for 9kw solar with future 10-12kwh powerwall

[mrpriceisright]

Trying to understand how PV panels connect to an inverter charger and powerwall.

Currently have 30 x 305watt panels (which put out dc 55v & approx 6 amps).
I can understand how a string split phase inverter is connected with several panels (5 or 6) in each string to produce 2 legs total 240v.

Planning on building 10-12kwh powerwall (48v?) to be added sooner rather than later.
What I am having difficulty understanding how an inverter charger would be connected to both the powerwall and PV panels, where the battery is 48v and the PV strings are >200v.

Looking for insights and suggestions on which inverters are suitable/capable of this scenario.
thanks

 

[Hedges]

"Powerwall" was an AC appliance, which interacted with GT PV inverters, also AC appliances.
Now that expression is being applied to other inverter/battery arrangements.

You can get a solar charge controller (SCC) which takes power from PV series/parallel array of some voltage and charges the 48V battery.
You can get an inverter/charger which combines the functions.
You can get a battery inverter with AC input transfer switch, and connect both loads and GT PV inverters downstream of it.

What sort of inverter do you plan for your Power Wall?

My system is all SMA. Sunny Island 48V battery inverter with internal transfer switch, and Sunny Boy GT PV inverter downstream (also my house loads)

 

[mrpriceisright]

Right. I was using the powerwall term generically: I was thinking of doing a DIY 48v battery (either one 12kwh or 2x 6kwh) using some EV / LifePo batteries. Something substantial enough to be able to run the house overnight.
As the inverter is such a big ticket item (particularly the high current ones), if possible it seems preferable to get a single inverter rather than 2 (one for the PV one for battery) if there is such a beast.

a

 

[Hedges]

What is your budget?
Electronics can run $500 to $5000, although for 9kW of PV it is probably at least the low thousands.

Traditional off-grid systems had an SCC (used to be PWM, now MPPT) from PV to battery. Then only one inverter, battery to AC.

You can buy a hybrid inverter, which includes PV inputs and battery connection. It is likely they have a feature of regulating battery current (e.g. keep it low if small battery) but utilizing full PV output if inverter draws more.

Some separate SCC (e.g. Victron) work with other components to deliver say 20A to battery as a maximum, but additional current when needed by inverter.

My SMA setup has a battery inverter that works with a grid-tie PV inverter. While the sun shines, whatever power comes from PV is power the battery inverter doesn't have to deliver. This works both as grid-tie and as off-grid.

Used EV batteries may be low cost but few if any are LiFePO4, so more fire hazard.
DIY LiFePO4 with cells from China is being done between the cost of FLA and AGM.

I use AGM. My system is grid-backup so size for deep cycle but infrequent, so that still has long enough life.
My SunXtender are on the more expensive side. 20 kWh gross, 14 kWh usable, $5000.

 

[Tecnodave]

Trying to understand how PV panels connect to an inverter charger and powerwall.

Currently have 30 x 305watt panels (which put out dc 55v & approx 6 amps).
I can understand how a string split phase inverter is connected with several panels (5 or 6) in each string to produce 2 legs total 240v.

Planning on building 10-12kwh powerwall (48v?) to be added sooner rather than later.
What I am having difficulty understanding how an inverter charger would be connected to both the powerwall and PV panels, where the battery is 48v and the PV strings are >200v.

Looking for insights and suggestions on which inverters are suitable/capable of this scenario.
thanks

MrPrice....
where in a grid tie system the panels are connected directly to the inverter, in a off grid or battery based system the solar panels are connected to a solar controller such as the MidNite Classic or Outback and from there to the batteries. Generally we do not use the higher voltages as the conversion from 200 volt from the panels to the charge voltages of the battery bank is not efficient and creates more wasted power as heat in the controller which reduces efficiency and makes the electronics hotter as heat is the enemy of electronics. Typically with your 96 cell panels we use strings of 2 for a string voltage of 110 volts on a nominal 48 volt system. My 24 volt systems have 72 cell panels with 2 in each string for 72 volts on 2 controllers and the other 2 controller has 96 cell Sanyo/Panasonic multilayer panels (amorphous polycrystalline over monocrystalline) all in parallel 53 volts at MPP to keep my voltage down conversion ratios in the range of 1.3 to 2.3. I have 4 main MPPT controllers and 2 auxiliary MPPT controllers....All American made, I don't like non programmable, non supported Chinese controllers. You have some learning ahead. My system is 100% standalone off grid, I will not be dependent on a grid,