The panel voltages you're seeing are meaningless with an MPPT controller. Only when compared to the amperage does the voltage become relevant. (multiplying the two values to ascertain wattage)

When discussing electricity, I like to compare it to water, as most people will understand the function more clearly. So, an MPPT controller is just an amperage gate. Think of it like a dam for a small pond. Water level is you voltage, how much water flows out the dam is your amperage. If the dam gates are fully closed, the water (voltage) fills up behind the dam. If the dam gates are fully open, the water drains all out leaving none to flow. If we set the gate just right, we find a perfect balance between maintaining a water level, while getting the most flow down the stream. And this is what the controller is doing. Finding that balance to achieve maximum wattage. Voltages are going to dance around while conditions change. And those conditions aren't just the environmental ones. State of charge of the batteries also affects this balance.

Back to the water analogy. Let's say the battery is a small town down stream, that has a water tower. As that water tower approaches full, and depending on how much water the townspeople are using from the water tower, the flow into the water tower needs to be modulated by the dam gates. And this too is what the controller is doing.

So fear not. Your system is functioning properly. Also, the reason you are going into float so quickly, is that your battery bank is simply not large enough to accept four hours of bulk charging. Setting it to two hours will not alter results. There's nothing wrong with the system going to float early. I think setting a cap on bulk time, is more a protection measure to reduce internal overheating of the batteries under heavy charge loading. Seems none of us ever have the problem of too many batteries, for this to ever be a factor.

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