Power Systems

[SpirckleM]

Ok, being a complete newby at this I just have to know, is there any reason why you would not want to have a 120 volt system instead of a 12 volt or 24?  Yes I realize that the additional batteries would cost more money but wouldn't you also have the advantage of not having to choose between hard to get appliances and transforming voltages from 12v or 24v up to 120?

The way I see it (forgetting about the money for a bit), if I had 20 12 volt batteries and split them into two banks and charged one up while using the other. I wouldn't have to transform at all, just convert from DC to AC.  To charge them I admit I would also have to have more solar and/or generate more voltage from a wind generator, but then by designing my own wouldn't I have some control over that?

Are there very good reasons other than the money for not using such a system?

[drdongle]

While your headed in the right direction you would actually need about 180 VDC as a 120 VAC is the RMS voltage ( nominal or average) and in reality peaks at about 170 volts. Such systems are available and in use and yes they are simpler in that you can do away with the conversion from 12/24/ or 48 volts to 120 VAC ( RMS). All you need is the H bridge and driver circuits.

[SpirckleM]

Is having two banks completely overkill, or is it perhaps insufficient?  Insufficient, that is, for having always on power system without having to worry about shutting it down at night or having too limited current output.

A 180 volt system would require 15 12volt batteries per bank for a total of 30 batteries, wow.  Ok now I'm starting to think about cost again, might run me close to $4000?

[drdongle]

Don't forget watts is watts, so you could use smaller amp hour batteries for a high voltage system. 1KW at 12 VDC is 82 Amps, 1KW at 180 volts is 5.4 amps.

So you could reduce the battery capacity and still have a healthy reserve.  

[wooferhound]

You don't need to alternate between 2 battery banks. You can charge the same battery bank that you are pulling your electricity from. Plus you still need an inverter to convert from DC to AC even if you are not changing the voltage. and again, what kinda AC do you want to get from your DC Battery Bank: sine wave, square wave ?

Square is easy

Sine is hard