Samil Solar river 4 KW invertor ?

Hi Folks i have been following the build your own powerwall video's and i just wondered how i might get this to work on my system once i built a battery pack ? I currently have a 4Kw solar array that is fed into a samil Solarriver inverter , Can the inverter take a battery input or do i need some more tech to add a power wall ?

Very interested in making my system work when the sun goes down. Any advice please ?

Paul

Yes it can be made to work, but you'll need quite a high pack voltage to mimic the PV input before it grid connects, and you'll need to current limit as the inverter will attempt to maximise its output.

I find grid tie inverters designed for wind turbines far more useful as they allow the current curve to be altered - which allows you to determine your pack discharge rate.

I know this is an old post and would like to add some information for the Smail inverters which can the be searched in the posts.

The solar River 4000TL-D (guessing this is the unit) has two MPPT inputs and each input self regulates the maximum average power throughput to around 2450W. Overall the maximum is 4000W but this can also be set by comand to be lower than 4000W (currently have mine set to around 2400W until I fix another issue..).

Each MPPT is current rated in the specs to 11A but the input voltage can sometimes be pulled as low as 100V so a 2400W limit at 100V would blow the MPPT. This took me a while to figure out as Samil will not disclose any details and have seen the operation through 1 second data from my unit. This regulation if it is on the power level rather than the current poses a risk for back feeding PV if the PV voltage is too low for the power level because the current will be incrreased above the 11A, hence the nabsolute must to either current regulate the input OR regulate the maximum output below the MPPT current handling level at your DC input voltage.

My planned approach to avoid having a DC battery pack with lethal voltages is to use a cheap standard 3000VA UPS attached to a 72V battery, pass the output through a bridge rectifier and add a small capacitor (ok, 92% efficient here). The DC here will then be passed through a surge suppressor (with relay bypass) to prevent a current surge into the inverter during the power on stage (have had issues with boost units blowing due to high initial current surges). The DC will then be limited by the inverter output and because in my instance I am using 230V AC the regulated DC voltage will be around 325V DC and for a 2400W output from the UPS the current level going into the inverter should then be closer to 7.5A, below the 11A limit..

In the instance of a dual MPPT input unit one of the inputs can remain attached to solar panels if required.

Not a conventional approach and not the most electrically efficient, however it provides a means to back feed to the grid with a grid approved inverter with off the shelf parts.