Array / Battery Bank Voltage Question

[openplanet]

I understand that the array VOC should ideally not exceed 2x the battery bank voltage.  My array VOC is 110V, controller is Classic 200, and battery bank is 24V.  My question is: how can I calculate the power currently being wasted due to the large down conversion, and the extra power gained if I up'd my battery bank to 48V?  Also, how significantly does the 110-to-24V down conversion affect the life expectancy of the Classic 200, compared to 110-to-48V?
Thank you.

[Westbranch]

The best you can do is to have the array at the nominal voltage of the battery, any variance from the Nom. voltage should be for a reason, such as the voltage loss due to the array being a long way away from the CC and Battery bank... using the same gauge wire as done on a closer array.

In actuality the powered used to convert is from the Vmp of the array, not the Voc down to the nominal battery voltage,
For my 4s arrays have a VMP of ~ 4 x 17.9V =71.6V
and the wire travels ~ 60 feet from array to battery...

So I chose to lessen the Voltage losses over that distance by starting with a higher V and smaller wire rather than buy larger wire.

Also the Minimum voltage needed for a 24Vbattery is = ~ 34V to power the CC and cover other losses in your system.

[Vic]

Hi o p,

Why not use the Classic String Sizer:
http://midnitesolar.com/sizingTool/displaySizing.php

And look at the projected power produced from your proposed array for a 24 V vs a 48 V system.

Generally,  Voc is only used to calculate the Maximum input voltage to the CC at the coldest temperature of record for the site.

Would always use String Vmp for all other calcs.

Depending on your location,  a string Voc of 110 V at STC might be fine on a Classic 150,  which would be a bit more efficient that would be the Cl 200.

IMO,  Vic

[russ_drinkwater]

I aim for double the bank voltage. And it seems to work well running through 150's with 24 volt banks. The distances are under 15 feet for me so less issues with losses.