I have a 100/30 that stopped working yesterday. I show 5 volts with the panels connected the controller, but if I remove the PV connections and measure the voltage while disconnected I get 30+ volts. I disconnected the 100/30 for several minutes. After reconnecting I get the same result. Has the unit failed. It is less than 2 years old. I have a 75/15. I connected it, and it shows more than 24 volts. Fuses are good.
You didn’t say where the 30V is coming from? From the batteries? Where are you taking the measurements from? Are your fuses working? Since you have another MPPT, why don’t you put that in the apparently broken MPPT’s place and observe what happens?
Thirty volts coming from the solar panels measured at the leads disconnected from the regulator. Batteries are showing around 26.The 75/15 showing around 27 volts at the moment. That’s a big cry from the 5 volts that the 100/30 was showing.
30V open circuit PV voltage to charge a 24V battery system is a bit low in general. PV needs to be 5V above battery voltage in order to start charging.
When the 75/15 was connected was it actually charging, was a current flowing, or was it sitting there with roughly the same voltage on both battery and PV side?
Roughly the same but batteries are full. When I got 30, volts will sun was going down. The 100 /30 had been charging well.
The problem is the very low voltage, 5, with the 100 /30 connected and the leads from the panels when disconnected from the regulator showing 30+ volts.
So its working? Then i dont see where the issue is. If theres no sun anymore, then the panels cant keep the output voltage up, that they fall down to a few volts with the MPPT as a load is normal.
But again, only 30V PV in full sun is just barely enough for a 24V system, if you have two panels in parallel for example, it would be better to connect them in series, to get a higher PV voltage