diy solar

diy solar

Votronic MPP 350 - Please help

Gbl

New Member
Joined
Feb 1, 2021
Messages
7
Hi,

I have a Votronic MPP 350 duo connected to a ECO Delta 330W solar panel

In sunshine the MPP light is flashing every 2 seconds, which the manual describes as “Display of readiness for service in case of missing solar power (at night)”.

Attaching a voltmeter to the solar connections while connected to the MPP shows 14.5v, but when I remove the solar positive from the MPP, the reading is 37.5v (please see attached pics).

Any help or explanation regarding the MPP light flashing would be greatly appreciated.

TIA
 

Attachments

  • D43233FC-B788-484C-BF63-FD36E48109C7.jpeg
    D43233FC-B788-484C-BF63-FD36E48109C7.jpeg
    135.6 KB · Views: 8
  • 98B7411D-74A8-4705-8340-BB9E86291BE6.jpeg
    98B7411D-74A8-4705-8340-BB9E86291BE6.jpeg
    144.9 KB · Views: 9
  • D1A65E11-2C5C-4F8B-A137-96C1B17BFBAD.jpeg
    D1A65E11-2C5C-4F8B-A137-96C1B17BFBAD.jpeg
    168.7 KB · Views: 9
What is the battery voltage? If the batt is charged (or nearly so) the controller could be intentionally running the panels at 14.5v to extract the required amount of power.

Typically MPPT will move Vpanel toward Voc instead of toward Vbatt, but in this case {assuming 72-cell variant} the 45.8Voc of the panel is butt-puckeringly close to the controller's 50v input max. Maybe the controller is smart enough to see that and look for lesser power points on the other/lower slope of the power curve.

{edited to add caveat}
 
Last edited:
What is the battery voltage? If the batt is charged (or nearly so) the controller could be intentionally running the panels at 14.5v to extract the required amount of power.

Typically MPPT will move Vpanel toward Voc instead of toward Vbatt, but in this case the 45.8Voc of the panel is butt-puckeringly close to the controller's 50v input max. Maybe the controller is smart enough to see that and look for lesser power points on the other/lower slope of the power curve.
Thanks for the reply.

Yes the battery is almost fully charged, in which case I would expect the “Batt Full” or “>80%” lights to be lit, rather than the MPP light.
 
I would expect the “Batt Full” or “>80%” lights to be lit
Good point.

Bad connection on the solar POS wire to charger POS terminal? It would explain the measurements, though I'm not sure what would cause it.

You've already done the disconnect panels, disconnect batt, reconnect batt, reconnect panels dance?

{or maybe the panel voltage it had to select is below the tip-in voltage for the MPPT function. Maybe add a load and see if it springs to life?}
 
Good point.

Bad connection on the solar POS wire to charger POS terminal? It would explain the measurements, though I'm not sure what would cause it.

You've already done the disconnect panels, disconnect batt, reconnect batt, reconnect panels dance?

{or maybe the panel voltage it had to select is below the tip-in voltage for the MPPT function. Maybe add a load and see if it springs to life?}
The connection seems fine as far as I can tell and I’ve tried the disconnect and reconnect sequence a couple of times, but no luck unfortunately.

Will try adding a load in case that helps...
 
The panel OC voltage is 38 volts so you are well within the operational range of the solar controller and i would expect to see 30v or higher when the controller is charging. Most MPPT controllers need to see a voltage higher than V batt plus 4 to 5 volts to start up. For the low reading consider, a faulty panel, not enough solar energy, serious shading on the panel, a high resistance connection in the panel connections to the controller, a faulty controller.
If you have a suitable meter to measure current, a DC clamp meter is ideal, you could measure the SC current of the panel. This is a maximum of 9 amps so within the capacity of most multimeters set to the 10A range. Set up the meter to measure current and connect to the solar panel cables. Ensure you revert the meter probes the voltage setting immediately after the test, (if you forget you will blow the internal fuse).

Its also possible to verify the panel is operational by connecting direct to the battery whilst monitoring voltage and/or current. Its useful to have a load of some sort on the battery whilst this test is carried out.

If you are able to verify the panel is supplying current then there may be a fault in the controller.

A final point are you sure the battery collected to the high power terminals of the 350 duo is the service, house, battery and not the starter battery.

The most likely issue is a poor connection in the positive or negative cables from the panel to the controller, perhaps at the MC4 connectors.

Mike
 
Last edited:
Thanks for the reply.

I’ll try to follow your suggestions to perform further checks.

Does the 37.5v reading at the end of the solar panel wires in the vehicle not rule out issues with the MC4 connectors and the panel?
 
Last edited:
Does the 37.5v reading at the end of the solar panel wires in the vehicle not rule out issues with the MC4 connectors and the panel?
The meter is a high resistance load and tales a very small current compared to that needed by the solar controller so any volt drop due to a poor connection would not be shown. To prove the panel and its connections to the input of the controller are OK, you need to disconnect from the controller and measure the short citcuit current. Its safe to have the meter set to 10A range and take a current measurement.

As I suggested another method to establish that the panel and its wiring is generating current is to connect direct to the 12v battery as a temporary test. Monitor the current and voltage and ideally load the battery with a suitable load taking several amps.

Mike
 
Thanks for the help.

All seemed fine with the solar, so bought a new MPP to try (with the intention of returning if it didn’t resolve the issue).

The new MPP is working, so must have been an issue with the old one.

Thanks
 
Back
Top