Array / Controller Voltage question

openplanet said:

I understand that ideally the array VOC should not be more than twice the battery bank voltage, so that the MPPT controller doesn't waste power down converting.  My array VOC is about 110V, controller is a Classic 200, and the battery bank is 24v.  How would I calculate the power lost in the current configuration, and the power gained if I moved to a 48v battery bank?
Thank you.

Calculate Power lost: Measure the Volts and Amps going into the Classic 200, while measuring the Volts and Amps coming out of the Classic 200. 

48 Volt Battery: Yes, a 48 Volt Battery configuration will be more efficient. You may need to go directly to the source ... email Midnite and ask them if they have any Graphs showing "Efficiency vs Input Volts (for 24 Volt Bank)" and "Efficiency vs Input Volts (for 48 Volt Bank)" for Classic 200. If they do not have a graph then maybe ask for a couple of data points.

a) Efficiency at 90 Vmp Input using 24 Volt bank
b) Efficiency at 90 Vmp Input using 48 Volt bank 

The Minimum Input Voltage should be about 130% of maximum Battery Voltage (ie during equalization).

They claim, the Midnite Classic 200-SL is "up to" 98% efficient.
It will be very interesting to see what efficiency you actually measure.