[RE-wrenches] Parts List For AC Couple Disconnect

[Dave Angelini Offgrid Solar]

Marc, High or low battery cut-out on a battery based inverter is lights
out. There is usually a warning period that becomes a fault. I still think
this is crazy for offgrid unless it is a very large system 20+KW of battery
inverters in a microgrid type mindset with onsight knowledgeable people.
Also lots of DC coupled solar.

Forgive me if I have missed something here as I have installed about 20
gensets for my California wildfire residents last month. Good Luck.

Dave Angelini Offgrid Solar
"we go where powerlines don't"
http://members.sti.net/offgridsolar/
e-mail offgridsolar at sti.net
text 209 813 0060

On Sun, 3 Nov 2019 09:38:51 -0800, Mark Frye <markf at berkeleysolar.com>
wrote:
> Hi William,
> 
> Thanks, you bring up issues that are important to me here.
> 
> In particular, my situation is that the GT inverter is inter-tied a 
> couple sub panels upstream of where I want to put the BB inverter. The 
> distance is long, so I am looking for a solution where I don't have to 
> run a cable between the two.
> 
> In general, I do wonder about using AC line voltage rise to take the Gt 
> inverters off line. The main goal is to prevent excess voltage at the 
> battery, so monitoring battery voltage is most direct, and there are 
> simple solutions for that.
> 
> Is AC line voltage a suitable metric for achieving the same goal?
> 
> Here is where I could use Wrench knowledge to confirm my thinking, that 
> being:
> 
> - With excess energy in the system, the charger moves it into the 
> battery, raising it's voltage until it reaches it high charging voltage 
> set point
> 
> - Once the battery reaches it's high voltage set point, the charger 
> stops putting energy into the battery
> 
> - With no other place to put the excess energy, the AC voltage rises
> 
> Am I getting this right, the reason to disconnect AC coupled inverters 
> when the battery if full is not to prevent the batteries from being 
> overcharged, but rather to prevent the AC line from becoming unstable?
> 
> I am hoping this is correct and that with $200 of industrial grade 
> devices from Digikey I can implement a robust control that will 
> disconnect the GT inverters before the AC line goes so high that the BB 
> inverter faults.
> 
> Mark
> 
> 
> 
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