Hi acei,
There are solar insolation maps available for the whole world--just google for a link.
24 or even 36 volts has many advantages over 12 volt. Here are some:
Wire size is rated in amps--so a #10 wire @ 12 volts can only do about 30 amps = 360 watts. Where as #10 wire @ 36 volts can do 1080 watts.
six six volts in series removes the issue of parallel balanced wiring.
The components in an inverter don't have to work as hard and are therefore likely more efficient when going from 36 volts DC to 120 volts AC.
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The parallel issue can be mitigated somewhat by using balanced wiring (see the smartgauge site if you wish to understand that better).
Statistically speaking the greater the number of cells the more likelihood there is of a failure. The other side of the coin is that when in series each cell must provide the full number of amps demanded. In parallel each cell only caries part of the load. For example:
6 series 6 = 12 volts; put a 100 amp load on and each cell must produce 100 amps. The weakest cell will limit the flow of current--so if one cell is "weak" and can only do 95 amps the bank will have that as an upper limit.
12 parallel 12 = 12 volts: put a 100 amp load on and each cell needs to produce only 50 amps. The weakest cell will NOT limit the flow of current so if one cell could do only 40 amps the other paralleled battery would do 60 amps to make up the difference (hopefully that never happens).
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The other problem with a 12 volt bank is that one weak cell may cause that battery in the parallel array to act as a parasite on the others, fairly quickly drawing the capacity of the other batteries down to the weakest cell.
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Right now on another thread someone is having issues trying to run a microwave on twin six volt jars. It runs for about four seconds and then the microwave shuts down. The inverter doesn't appear to be going to fail over condition. His problem is simple. Six volt batteries, with their thicker plates, are not intended for high amperage loads. Twin 12 volt batteries would easily be able to do what he wishes, if they are wired like this:
As it often doesn't cost a dime more to do this, I think it is worth the trouble.
