PWM input voltage, Xantrex C40 test video

Looking at the schematic and believing MrWizard's reading this is what must be happening. Even when the controller should be on all the time, max charging, it is not. There must be a small time that the controller is off and the panel voltage is at V open circuit, the volt meter is averaging the voltage to get what MrWizard is seeing. This is not an uncommon situation with PWM. There really is no way to know really what the voltages are without using a scope and each brand controller could be quite different and still be called PWM.

Here is another question that I don't think has been asked. If the controller is pulse width modulating the panel voltage it also must be pulse width modulating the current to the battery. So the current that is being read as charge current is an average current, not a constant DC current.


MrWizard wrote:

"if you have a DC power supply with a voltage at a set voltage powering equipment that voltage will not change unless the load exceeds the ability of the power supply" TRUE

"the panels are a pure DC power supply the controller is the voltage regulator" FALSE -- the panels are current sources.

Thanks for doing the fuse.

If your Bulk setting is 14.5 and the controller output is at 14.6, doesn't that mean it is finished Bulk and is now controlling with a PWM duty cycle??

It would be good to get the input voltage when the output voltage is still around 13v in the morning on a sunny day before the controller starts controlling.

I suppose with the higher than battery voltage at output, you need to allow something when setting Bulk and Float. Do you add a bit more for Bulk (high amps) and not much for Float (low amps)? I don't know what would work best, something to learn! I know you discussed before about the controller location and your choice about that, so what is the work-around for voltage settings?

1:57 PM PDT 91*F
parked in the shade, 3100w inverter generator running, for A/C
wfco output is reading 10amps
inverter use is reading 9.8 amps
solar reading
above fuse 16.55v
below fuse 16.52v
controller output 14.60v 8.59amps
voltage at batteries 14.22v

IIRC my bulk setting is at 14.5v
i know i changed it a while back because it was too low
my batteries almost never get there,
only IF i'm in the sun and the Generator is running
even then they rarely read 14.2 at the batteries
this time of the year there is almost always something running
like multiple fans, the TV or the PC
so yes i would say i'm still was in bulk
i would say they might spend a couple hours per day where they are intermittently at 14.1

Sundays when i usually do my top charging, they get to hold a steady voltage for a few hours

The video shows as load increases the fluke reading decreases, it also shows as sun increases, the fluke reading increases.

As load increases the duty cycle increases (less time at Voc, more time at Vbatt+), there is available panel power not being used

As sun increases, the panel has even more available power not needed so the duty cycle decreases (more time at Voc, less time a Vbatt+)

Fluke Voc only when NO load.

Well you can't answer whether it is in Bulk unless you can tell when it is.

You do know the battery voltage you set for "Bulk" and you know if the battery voltage is below that and climbing with good amps, so that would be "Bulk" when the array side should be battery voltage plus line loss. (with most PWMs anyway)

Once the battery gets to that Bulk setting, the controller starts controlling and now I am unclear what that array side voltage would be, with all that duty cycle business.

The C40 is supposed to hold the voltage at the Bulk setting (often called Vabs)for a timed one hour and then go to the Float setting.

Some controllers say on their displays whether they are in Bulk or Float but that is with MPPT where I suppose the MPPT being "on" can trigger the Bulk notice on the display.

i have had 17v at 23amps charge . 14.xx volts
to me that is still bulk, or what ever you want to call it
i do not consider that float, maybe others would

i think i have a video showing 16.xx and 20+ amps, just under 17v

MrWizard wrote:
i think, the only time my array is at VOC is IF I disconnect it from the controller, VOC is 22+ volts, i have never read that with the panels connected

Correct. The mystery here is if you get higher than battery voltage plus line loss at the array side of the controller when the controller is in Bulk. So to be clear, do you get that 17v in Bulk?

If you only get that 17 or 18v in Float or perhaps in the timed one hour at Vabs before it goes to Float, then it could be that meter averaging thing for the duty cycle.

i think, the only time my array is at VOC is IF I disconnect it from the controller, VOC is 22+ volts, i have never read that with the panels connected

Now I have some internet time, I will continue to solve this ! :)
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EDIT--see crewzer in this link below--re "duty cycle" etc--some here mentioned that earlier too, but he does a calculation

http://forum.solar-electric.com/forum/solar-electric-power-wind-power-balance-of-system/advanced-solar-electric-technical-forum/1164-c40-or-ts45-max-voltage-question

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Saw the video in the OP--Mr Wiz has an accent! :) My question, not answered yet, was if the panel voltage was taken on the other side of that disconnect fuse and so might the that fuse have a high R creating that 17v? So that is why I asked it the voltage could be taken right at the controller terminals to see if there it is at battery voltage.

So far I found this answer in a forum where somebody asked about his C40 by someone who has one (no link, sorry)

"If the battery is full, the C40 stops charging and the PV array drifts to it's Voc point. When the battery is low, it connects to the PV, and pulls the PV voltage down to the battery voltage."

It was also mentioned that it is PWM and not MPPT by somebody who wished it were MPPT.

I also found a schematic but it is hard to read (the layout one has a zoom though)

http://www.waghornswood.net.nz/Manuals/Solar_power/Controllers/Trace_engineering_Xantrex/index.html

In this strange conversation, it opne where the guy says the CC drops it to 14, but not clear. The staff answer next is clear enough.

http://www.solarpaneltalk.com/showthread.php?12899-Xantrex-C60-PWM-CC-input-voltage-up-to-55V