12v or 24v in this situation

Re: 12v or 24v in this situation

BigBrosMo wrote: »

Hi there, I think this is a simple question but I am really having a hard time finding a simple answer! I am currently using a 12v system, 3 x 24v panels @ 280w and a 30A MPPT controller to fill 4 x 160Ah batteries at 12v. I then use a 1000w, 12v to 220 Inverter.

Simply put, is there any advantage of changing it up to a 24v system? ie. Recable the batteries so there are 2 banks of 24v, then use a 24v to 220v AC inverter? My MPPT controller accepts either 12v or 24v batteries. Will it charge the batteries "faster" or more efficiently if they are in 24v strings rather than 12v? Or am I already getting the same charging efficiency from 12v that I would from 24v by already having the MPPT?

Welcome to the forum,

One of the main advantages of going 24 volts for you is that your batteries will be in two parallel strings, rather than four strings. That will be a huge advantage for your batteries because parallel battery banks are unstable. short discussion here:
http://forum.solar-electric.com/showthread.php?14674

How are your panels configured (three in series or in parallel?) What is the Vmp and Voc of the panels? What is the Vmax of your controller? The reason I ask is that depending on the Vmp of your panels, they may have to be in series to charge a 24 volt battery. If they are in series, the Voc of the string may exceed the Vmax of the controller.

As far as charging efficiency is concerned, your MPPT controller will be most efficient when down converting from a string Vmp that is 15 - 20 volts above your nominal battery voltage.

You asked about whether a 24 volt system would be better for your batteries. The answer is yes, but I wouldn't necessarily change your system just for the sake of your batteries... your batteries are ephemeral. (how old are they now?) More importantly, does a 12 volt system meet your needs? If so, save some money by not upgrading and put the money into your "next battery fund".

--vtMaps