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maartenbornauw asked

MPPT 100/20 always in error21, MPPT 75/15 on sime installation all OK

Hello everyone,


I have a friend who has a very simple setup with an MPPT100/20 smart charger.
She has 2 panels in parallel of 130W each (42V panels), and a 100Ah LifePo battery.

On the load only a led strip and USB port to charge her phone. She uses between 20 and 40Wh per day.

Few days after I installed the MPPT 100/20, it gave error21. Checked everything, and could not find a problem in the setup of the wiring. Went to only one panel, no diffrence. Error 21.

Did the reset thing, and when only connecting 1 of the poles of the panel (negative or positive, doesn't matter) the error 21 is already set (without the possibility that the MPPT is measuring something from the panel, hence only one cable is connected). I always used the connecting sequence as per manual.

Supplior took in the MPPT 100/20 (warranty) and says nothing is wrong. Sends it back at our expense (shipping to them also at our expence). While the MPPT 100/20 is away, I used my own (old) MPPT 75/15 with the one panel to full satisfaction. Everything works OK.

Got back the tested and good (according to the vendor) MPPT 100/20 and put it back (with only one panel connected). Again, after 1 day error 21. Now the supplior wants us the remove the load and says that the way the MPPT 100/20 is build, is completely diffrent than the 75/15, therefore it is no reference. It is not designed to handle a load?

I have a long experience in troubleshooting DC systems in cars and motorcycles, but I am baffled here. Espacially by the aftersales of this very known vendor.

What to do here? Can someone explain me (technically) how this is possible? I think the current sensor is measuring the tension drop over a very small calibrated resistance in the ground path (ground of panel and battery are connected, I measured 0.3 Ohms.).

I just want this thing to work without me changing everything every few days because of a basically bad aftersales of the vendor.

Long story, but just tried to be complete.
Thanks


Kind regards,

Maarten

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2 Answers
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Alexandra answered ·

@MaartenBornauw

What voltage battery system, is it 12v? in the manual for the 100/20 with some battery voltages the max it can run is 1A, so it really should be signalling something else.

error 21 is a current sensing issue. removing the load seems the best option right now use a relay that is controlled by the load output to power the load from the battery instead. it might be there is a high current start up on the led strip? just guessing here, some electronics are just strange loads.

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maartenbornauw answered ·

@Alexandra

Thank you for your fast reply.

The system is on a 12v battery.

I’ll try to move the load, but why would the 100/20 give the error on the PV current sensor when the load peaks? It is possible since it is all interconnected, but strange. Or is there just one current sensor?

The 75/15 handles it all perfectly well, that is the strangest thing.



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Alexandra avatar image Alexandra ♦ commented ·

I agree, it does seem strange. Have you tried measuring the inrush of the led strip and other loads at all?

The current sense works for the PV and load/charger side as far as I understand. It is 20A total out put including charging/load.

You are not over panelled. 130W at 42v is like 3A (so the short circuit rating is a bit above that). So 6A input 2 in Parallel is good. So I doubt the error is related to that.


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