question

As you guessed it is quite likely it switched itself to 24V mode. It has happened to me in much the same situation and a few others if you search the forum.

How to change back without BT or USB dongle I don't know. Find someone near you that has the necessary equipment perhaps?

To reset the usual thing to do is disconnect all and reconnect in order. a) battery, b) PV c) load

Disconnect in reverse order of above.

If that doesn't work at least reconnect with only one PV or connect in parrallel to reduce the MPPT input voltage - you don't say what the output voltage of the panels are.

Thank you for your replies!

1. Don’t have papers anymore but i assume panels are 12v.

2. I tried disconnecting the battery and solar panels, but i didnt disconnect the actual wires from controller. I just made sure that no voltage goes in (from panels) or out (to battery) of it and that nothing blinks on it. Do you think pulling out the cables would make any difference? My controller is just hidden and very hard to reach, possible but troublesome.

3. I cant do the re-wiring of panels because shops are closed and i dont have stuff, but i could connect my second battery (back up one which i dont normally use) to the main battery. My main battery is 130ah and the backup one is 170ah. Different brands but both deep cycle. Is charging 2 batteries too much for 2 panels?

Thanks for your help, really appreciate it!

If you disconnect all power the MPPT and leave it for few days it will return auto detect mode and set the voltage you connect to 12 or 24. Thats an option if you dont have the kit to connect.

Hi andzei, I can also confirm your overcharging behavior.

My Blue Solar MPPT7515 has switched itself from 12V to 24V charging setup after 20month faultless operation on a 12V 80Ah Gel Battery. PV Module has 200Wpeak and 34V open circuit voltage.

The battery voltage charging range has been from 11.8V to 14.5V when the Blue Solar MPPT 75/15 was in operation for over 1.5 years.

The Jumper was between Pin2 and Pin3.

Since commissioning, there has been no modification to the system.

Without intervention the MPPT 75/15 suddenly charges the 12V battery to >17V when PV Power is available.

It seems that the unit loses its initial configuration and switches to dangerous 24V Setup although using still a 12V battery.

The analysis with the dongle showed that the unit has set itself to 24V.

Without the dongle, it is not possible to check the correct voltage setting.

The status LEDs cannot indicate whether the MPPT7515 is in 12V charging mode or 24V charging mode.

The overcharging due to the MPPT 7515 has heated the battery up. It has lost capacity due to constant overcharging and has now a high internal resistance.

Victron could not confirm if it is even allowed to operate the Blue Solar without supervision.

It would be beneficial to contact the insurance company to see if any damage triggered by blue solar MPPT7515 would be covered.

This dangerous condition for battery and surrounding can only be interrupted by manually disconnecting the battery or PV system.

The blue solar MPPT7515 unit shows no error and charges at full power, as the 12V battery for the solar controller appears as an empty 24V battery.

It´s interesting that Victron got the CERTIFIED ELECTRICAL SAFETY Standard from UL and CSA with the behavior, that the MPPT 75/15 switches itself to a higher battery voltage without any reason.

Without the dongle it is not possible to determine, whether the blue solar is in 12V or 24V mode.

A disconnection of PV Module and Battery and a restart after 48h did not lead to any improvement.

It is already a matter of several concerned systems, as various forums are pointing out the overcharging topic with statements like “MPPT7515 stuck in Bulk Charge Mode”.

To reset the unit to 12V operation, a chargeable 60Dollar Dongle and an update to V1.56 is necessary.

Device safety in the delivery condition is apparently not guaranteed.

@Dave van Dongen

@Steve

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