Aucune tension PV sur MPPT 250/100-MC4

[Camomille]

salut à vous,

je reste à 0 V (dans Victron Connect) lorsque je connecte un string sur une entrée de mon MPPT 250/100-MC4.

J’emploie une boite de connexion ( https://nl.aliexpress.com/item/1005006441008694.html?spm=a2g0o.order_list.order_list_main.17.2e675e5baggNBC&gatewayAdapt=glo2nld ) entre les panneaux et le MPPT.

La tension de sortie de cette boite est correcte (+/- 210V) mais devient nulle lorsqu’elle est connectée au MPPT !??!

Pour être certain de la polarité je suis parti du principe que le négatif est commun aux entrées Batterie et PV, ’ai testé au multimètre.

Entre les entées PV - et le + de la batterie, j’ai bien une tension correcte (53V). Bizarrement, j’ai la même tension en faisant la mesure

entre les entrés PV + et le + de la batterie.

J’en conclue qu’il y a un problème avec le MPPT. Une installation identique (avec un MPPT 250/100-TR cette fois) fonctionne parfaitement!

J’aimerais connaitre votre avis avant de demander un remplacement de mon appareil. peut-être ai-je oublié un détail? Je suis certain d’avoir

respecté les polarités des branchements PV !

je vous remercie d’avance.

Bien amicalement.

Camomille

[MikeD (Mike)]

@Camomille

The output voltage of this box is correct (+/- 210V) but becomes zero when connected to the MPPT??!

To be sure of the polarity I assumed that the negative is common to the Battery and PV inputs, I tested it with a multimeter.

Between the PV inputs - and the + of the battery, I have a correct voltage (53V). Strangely, I have the same blood pressure when doing the measurement

between the PV+ and + inputs of the battery.

There are two reasons that the PV input drops to zero when connected to the MPPT unit:

1. Polarity reversal: If the PV+ from the modules is incorrectly wired to the PV- of the MPPT, then there is an input protection diode that will clamp the voltage to between -0.5 and -1V

2. The input is over voltage. This will trigger the input voltage protection of the MPPT, which will clamp the voltage to <1V.

If there is high input current in either condition, then it may destroy the input protection device.

This can be tested by removing all connections to the MPPT, and testing with an ohm meter from PV+ to PV- . If your multimeter has a diode test function, that can be used too. It should be open circuit with + to PV+ in, and 0.4V with - to PV+ in.

Also carefully check the voltage on the MC4 connections/cables from your connection box to the MPPT.

when working correctly, the voltage from PV+in to battery +ve should be ~ 150V. (Vsolar - Vbatt)

[Camomille]

Thank you for this complete guide.
Here are the values found using diode test function:
PV+ in to PV- in : open
And here is what I found using DC Voltmeter:
BAT + to PV+ in : 0.08 V
BAT - to PV+ in : 0.03 V
I’m 100% I did not invert polarity. I have made and onnected only one (double) cable with MC4 connectors at one end. Male connector bringing positive current from PV into female connector on the MPPT.
There’s no doubt I have received a faulty MPPT. I’ll check this with the seller!

Great thanks for your help.
Best regards from Belgium.
Camomille