I have a Bluesolar MPPT 150/60 that was first used in 12 V system. Before starting to use it in another 48 V system I first changed the internal battery voltage setting. Now it goes into float mode before the batteries are fully loaded (according to the BMV they are only 65 % loaded). During daytime the system tension goes up to around 57 V but during nighttime it goes below 51 V. Is there some other setting I need to change to get the batteries fully loaded.