Classic 250 Charge Current

[elbrechtel]

Hi all,

I struggle to find a good calculator to determine voltage drops with, what is your favorite one?

B

[Halfcrazy]

Hi all,

I struggle to find a good calculator to determine voltage drops with, what is your favorite one?

B

I really like this one: http://www.calculator.net/voltage-drop-calculator.html

[elbrechtel]

Thank you! that helps a lot!

[elbrechtel]

Hi,

Can I hang 2 midnite controllers in parallel on 1 string? Or do i need to run two cables to each array separately? ( 4 in total)

thanks!

Brecht

[vtmaps]

Can I hang 2 midnite controllers in parallel on 1 string? Or do i need to run two cables to each array separately? ( 4 in total)

No.  see reply #12 in this thread... I think you're asking the same question... if not please clarify.   --vtMaps

[elbrechtel]

Excuse me, i thought i had asked this question on another forum.
My apologies, haven't slept a lot!

B

[tecnodave]

Mahendra,

that will be cool but would it also work for classics of different voltages and well as different pv voltages?

My understanding of the full parallel operation as implemented in the kid is inputs and outputs are tied in parallel and that the MPPT functions would have to be sync'ed as well so, no this kind of paralleling will not work with Classic's with different inputs. Full paralleling of the Classic's would be inputs and outputs connected together to handle larger loads. Paralleling only the outputs with separate inputs as implemented in follow me mode only shares charge state and set point, not the MPPT loading of each input.

td

[boB]

Right now, we cannot parallel inputs of more than one Classic.

Only the outputs of different Classics can connect to the same battery.

However, in some wind-turbine installations, there have been successful input paralleling
of multiple Classics when each Classic has their own 3-phase rectifier coming from
the same turbine.  Different thing than solar though but thought I would mention it.

[dgd]

Right now, we cannot parallel inputs of more than one Classic.

Only the outputs of different Classics can connect to the same battery.

However, in some wind-turbine installations, there have been successful input paralleling
of multiple Classics when each Classic has their own 3-phase rectifier coming from
the same turbine.  Different thing than solar though but thought I would mention it.

Now thats an interesting idea..
So the only separation between the two Classics in a wind application is the two three phase rectifiers which are no more than diodes. So I presume one function these diodes serve is to isolate the inputs of the two Classics from each other?
So would the same not work with two Classics connected to the same PV array?  simpoly by using a decent size diode to isolate the +ve input to each Classic?

dgd

[TomW]

Right now, we cannot parallel inputs of more than one Classic.

Only the outputs of different Classics can connect to the same battery.

However, in some wind-turbine installations, there have been successful input paralleling
of multiple Classics when each Classic has their own 3-phase rectifier coming from
the same turbine.  Different thing than solar though but thought I would mention it.

Now thats an interesting idea..
So the only separation between the two Classics in a wind application is the two three phase rectifiers which are no more than diodes. So I presume one function these diodes serve is to isolate the inputs of the two Classics from each other?
So would the same not work with two Classics connected to the same PV array?  simpoly by using a decent size diode to isolate the +ve input to each Classic?

dgd

Sounds like an experiment for our resident Classic destroyer, Ryan! See if he can make one or both release the mystical smoke.

Seems a single  bridge be plenty of isolation on a DC source?

Tom

[dgd]

So would the same not work with two Classics connected to the same PV array?  simpoly by using a decent size diode to isolate the +ve input to each Classic?

Sounds like an experiment for our resident Classic destroyer, Ryan! See if he can make one or both release the mystical smoke.

Seems a single  bridge be plenty of isolation on a DC source?

Just thinking about this and does the same apply with DC turbine/Clipper that two Classics can be connected to the Clipper to divide the load between Classics?
The input to the second Classic would need to have another diode (or second rectifier same as Clipper currently uses)
connected to inputs to Clipper's rectifier?
I suspect it would be necessary to use an identical 3ph bridge rectifier where the +ve from turbine goes to commoned 3ph inputs and only +ve output from retifier is used and connects to Classic, hence using 3 diodes of the bridge.
This would mean balanced DC outputs to Classics. IMHO.

The part I don't get is how to ensure the Classics get a near equal proportion of the input power. Perhaps this is just relying on the input impedence of similar Classics being quite closely the same.
Maybe it would not work with different models of Classic or a Classic/KID combo (but would be real nice if it did) 

I like the Ryan idea     Will he try it?

dgd

[tecnodave]

Right now, we cannot parallel inputs of more than one Classic.

Only the outputs of different Classics can connect to the same battery.

However, in some wind-turbine installations, there have been successful input paralleling
of multiple Classics when each Classic has their own 3-phase rectifier coming from
the same turbine.  Different thing than solar though but thought I would mention it.

Now thats an interesting idea..
So the only separation between the two Classics in a wind application is the two three phase rectifiers which are no more than diodes. So I presume one function these diodes serve is to isolate the inputs of the two Classics from each other?
So would the same not work with two Classics connected to the same PV array?  simpoly by using a decent size diode to isolate the +ve input to each Classic?

dgd

I think that the difference here is that in wind mode the Classic is working with values programmed into the wind curve for that wind generator, it knows the rpm,s from the pulsing on the generator signal ans sets up the correct MPPT from that data where in solar mode the controller sweeps the voltage from Vmax to some value maybe 50 % of Vmax to find the Maximum power point. The Classic logic would need to be linked somehow to cause the sweeps to be in tandem or better yet only 1 Classic does a sweep then tells the other what set points to use. In any case it is not trivial. A huge amount of programming will be needed to accomplish this.

td

[dgd]

I think that the difference here is that in wind mode the Classic is working with values programmed into the wind curve for that wind generator, it knows the rpm,s from the pulsing on the generator signal ans sets up the correct MPPT from that data where in solar mode the controller sweeps the voltage from Vmax to some value maybe 50 % of Vmax to find the Maximum power point. The Classic logic would need to be linked somehow to cause the sweeps to be in tandem or better yet only 1 Classic does a sweep then tells the other what set points to use. In any case it is not trivial. A huge amount of programming will be needed to accomplish this.

I am not actually sure this would be case or a requirement to have the MPPT scanning somehow synchronised.
If, for example, a 6Kw PV array was connected to two Classics via protection/isolation diodes then ideally you would want 3Kw power through each as a maximum. It would not really matter if below a full power input the division of power between the Classics was different. You just do not want all 6Kw trying to squeeze through one Classic.

There is already a Classic setup parameter that specifies the maximum input and output currents that the Classic can process. So just specify 3kw worth of amps in each Classic and let them sort out individually what they want to do.
I can't see any reason this would not work. The Classics cannot 'see' each other so should just see a varying PV input as if just connected to its own array.

dgd

[tecnodave]

I am not actually sure this would be case or a requirement to have the MPPT scanning somehow

I can't see any reason this would not work. The Classics cannot 'see' each other so should just see a varying PV input as if just connected to its own array.

dgd

I think that you are not looking at the issue, When one Classic does an MPPT sweep it will pull down the PV input voltage at least to some degree , at that point it will cause the other one to sweep and I would think that you would have an unstable loop in which the classics would fight for control and result in an unstable oscillation.  In any case there are only two companies who are doing true paralleling of inputs and outputs. It is difficult to achieve.

[dgd]

I think that you are not looking at the issue, When one Classic does an MPPT sweep it will pull down the PV input voltage at least to some degree , at that point it will cause the other one to sweep and I would think that you would have an unstable loop in which the classics would fight for control and result in an unstable oscillation.  In any case there are only two companies who are doing true paralleling of inputs and outputs. It is difficult to achieve.

Ok,maybe you are correct.  We don't really know what would happen until it's tried and with configurable current limits, mppt sweep depths and intervals there may be possibility they could work together..

Dgd