boB ✭✭✭

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boB
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  • Re: MPPT charge controller

    This is pretty low power for a typical MPPT controller system.  About 30 watts maybe ? Hard for me to tell voltages too closely but low PV voltage looks to be around 16.x volts and high current maybe 2 amps or so ?

    What is the current scale reading ? If it's the battery current, then it kinda looks like the maximum power point PV voltage is more like 16 or 16.5 volts, which is corresponding to maximum power into the battery. (If showing Batt current)  That should be OK for a low battery.

    MPPT controllers will normally have some amount of voltage drop between battery voltage and PV voltage at however close to 100% duty cycle it can obtain.  A higher input voltage will help that issue.

    Also, if it's battery voltage being shown, if it is measuring the MPP voltage accurately, looks like the MPP V happens when the controller first drops the PV input voltage down low and would be wasting energy the rest of the time since it is off the max power point. That would
    always be the case too it is always changing.  Again, it's hard to read max power point at low powers, but it would not change in a sawtooth pattern like this.
    Even it it's measuring PV current, they will both be pretty close at this small-ish voltage difference.

    Just 2 cents for today.
    boB







  • Re: Very close to max wattage on my Classic 200

    10,000 feet, eh ?  The modules should put out a bit more up that high.  Less air for cooling too.  I know that Classics have been operating up at that high of altitude but I haven't been to any of those installations so I'm not sure what to expect.

    Maybe just try it and report back ?  The Classic may limit itself, current-wise.  If it does limit the current, it does this by raising the input voltage and so the Classic MAY get a bit hotter.

    boB
  • Re: Batteries not reaching float

    While under charge with a good amount of current into the batteries, check the temperature of the batteries, if even just with your hands to see if one of them is HOT.  A temperature imaging camera is the best but we don't always have one of those laying around.

    Temperature seems a good way to find where all the extra wattage is going.
  • Re: amp discrepancy ?

    When you see this happen at low amps like this, try turning the Classic off and back on again or better, go into the MODE menu and turn the mode off and back on.  See if that makes it come back in line with the Trimetric and/or WB Jr. in case drift was a problem

    The current sense in the Classic is very good but it's not perfect and has to be adjusted carefully at the factory...  Also, battery current should be a wee more accurate than input PV current.

    The  internal shunts look at the positive lines where the Trimetric and WB Jr. measures at the negative line into the battery - terminal.

    FYI, the common negative line from the Classic terminal, if only one single wire is used to tie to battery negative/common, will show difference between input and output current of the Classic, so just be aware of that.  That isn't a problem with the common shunt to battery minus though because the everything else is tied at the battery minus bus.

    There IS an adjustment pot accessible but I wouldn't touch that one just yet.

    boB