>yaaa
my system size is 40KW.
my system size is 40KW.
A PV array of 40,000 watts at 120 vdc nominal?
Thats still 333.33 amps without the UL/NEC 156%!
If I multiply that by 4 hours of equivalent full rated charge we are looking at 1,333.32 amp hours at 120 vdc nominal!
If I multiply that by a factor of 5 to size a battery bank, thats 6,666.6 amp hours at 120 vdc nominal battery bank!
Industrial motor controls use magnetic starters. For example; a 120 vac single phase, less than 1 amp draw coil, is used to "pull in" a starter that connects a higher voltage and amperage motor circuit like say, 480 vac 3 phase at 100 amps. An automobile starter works on this same principle only they are all they same voltage, just higher cranking amps. Old timey cars and trucks used to have something like the old foot operated headlight high/low switch only the foot operated stater button was normally open and momentary and it connected the full amperage from the battery to the starter when depressed. The key switch simply turned on the ignition. But enough of that.
If one could build a sensor that could read 120vdc nominal battery voltage as compared to 120 vdc nominal PV array voltage and make the high/low setting field selectable and that could "pull in" or "drop out" several contactors of a higher amperage rating in accordance... Your problem would be solved. This would in effect be a simple on/off charge controller technology similar to the Trace C30's. One problem would be that at higher dc amperages, the contacts have a greater tendency to weld together. This might be overcome by reducing the amprage with several sub-arrays and multiple contactors. If one does weld together, enough of the other contactors could open there by reducing the over all charge. As with any system of this nature redundancies and alarms may be necessary. PLC's would be a nice touch. Just an idea.
This is the closest thing I could find to what you are seeking that is, more or less, "off the shelf." It actually does more than what you may need but as James pointed out, a custom piece may have to be built. Good luck!
http://www.tmiestore.co.in/newpdf/Solar/SolarChargeControllers/MPR9400.pdf
http://www.tmiestore.co.in/solar.htm
