Ben Okopnik wrote: > >>> In addition, current in a pair of paralleled generators is additive; >>> current from a larger one will not flow through a smaller one, since >>> there's no voltage differential, but will simply be added to the total. >>> >>> >> If there is a differential when not connected, then current will either >> flow from one to the other (and the load) or from the higher potential >> to the load if the lower potential source will not allow incoming >> current. >> > > The second part of this sentence is correct: a source will not allow > incoming current, so it all goes to the load. Hence, additive currents. > > >> That is true if the load is of a high enough resistance to >> permit the voltage at the connection between the two generators to >> remain above the potential of the lower potential source. >> > > Unfortunately, this isn't an accurate description: the resistance of the > load does not make any difference to the interaction of the two sources. > They are additive, regardless of what the load does. > In this case, I'm ignoring the load on the output of the controller. I'm speaking of the load placed on the voltage sources by the input of the controller. Let's replace the controller for sake of discussion with a resistor. Then what I'm saying is accurate. Now let's replace the resistor with the controller. I don't have one so I can't say for sure, but if the controller does not dump excess input power the effective resistance of the input circuit will have to vary based on the load on the output of the controller. > >> Yes, if the controller has a low input resistance as I mentioned, both >> sources will feed current to the controller. I was merely thinking out >> loud about what that resistance would have to be. I used the term >> impedance because I'm fairly certain that the circuit is not 100% >> resistive in nature and will have some reactance but I'm not completely >> certain of that. >> > > But that will not matter, since the input voltage is purely DC > > >> If so then my use of the term impedance is at least >> tolerable. ;) I can run a simulation of various loads to demonstrate >> my contention, if you wish. >> > > Given an average input current of 20A (as in my configuration) and the > fact that I don't see a capacitor or inductor of any significant size on > the controller board, I'd be fascinated to see any sort of analysis that > supports that point. :) >
>> That said, can anyone tell me what the input voltage does when the load >> on the controller is removed? Does it go up or does the controller dump >> the excess current into an internal load. >> > > Depends on the type, of course. I'm not familiar with any MPPT > controllers that use an external load; assuming one without, the input > voltage will, of course, rise. > > Incidentally, my best guess for how these things work is that they're > very efficient DC-DC converters: chop the incoming power, convert it > down to 14.4v (or whatever their nominal voltage is), and collect your > ill-gotten gains in current. I recall doing this at the mW level > while designing drivers for millimeter-wave radar at Hughes Aircraft, > but this is certainly a very nice application of the principle (assuming > my guess is correct.) > I agree, that looks like what they are doing. Great design. > > _______________________________________________ Liveaboard mailing list [email protected] To adjust your membership settings over the web http://www.liveaboardnow.org/mailman/listinfo/liveaboard To subscribe send an email to [email protected] To unsubscribe send an email to [email protected] The archives are at http://www.liveaboardnow.org/pipermail/liveaboard/ To search the archives http://www.mail-archive.com/[email protected] The Mailman Users Guide can be found here http://www.gnu.org/software/mailman/mailman-member/index.html
