Yet Another Strange Electrical Glitch!

[Rick D]

So, my solar regulator would not produce significant wattage. (Victron 100/200 MPPT). I did a firmware upgrade and thought that might be the problem. FYI, 500 (ha!) watts of solar. The battery display on the app showed 13.8 volts and float while Link 2000 house display showed 50% on new batteries (450 amp hour AGM). I assumed a reboot of the unit was needed so I disconnected the hot leads from the solar and batteries. After five minutes, I reconnected them with no change. Then I checked the battery in voltage on the regulator with a multimeter. It was indeed 13.8 volts when the battery was in fact 12.3. The battery leads in from the battery switch. So, I bypassed the leads from the battery switch and went directly from the house batteries to the solar regulator. Eureka, it worked and the solar was now putting out full amps.
So, the weird part is why now? This has worked fine for five plus years. Another oddity is that the battery selector switch did not turn off in the OFF position when I tried it. There was still current flowing to the switch panel. So, clearly, I have a problem with the selector switch and I will replace it. But how the heck did I get 13.8 volts feeding from it to the solar regulator??? My first thought was a failure in the battery isolator and feedback from the start battery, but it would have had a resting voltage of 12.6-ish and certainly not 13.8. Fun and games when away from the dock for a couple of weeks...

 

[dlochner]

It would be helpful to see a schematic of the electrical system, because I have no idea how your system is wired.

Second, the sequence of powering up a Victron controller is important. The connection from the battery to the controller must be made first and then the connection from the panels to the controller can be made. If the sequence is reversed, the controller will look like it is operating, i.e., it will show panel voltage but will not supply current to the battery.

 

[Davidasailor26]

My guess is the switch is going bad and adds high resistance between the batteries and solar charger. Then the charger puts out enough current to “float” the batteries at 13.8, but the voltage drop across the switch means the batteries themselves are still sitting close to their resting voltage.