TalkBaja.com » Baja Mexico Forums » Off-Grid / Solar, Wind or Generator?

For those of you with off-grid systems, I am just curious which system DC voltage(s) you run and why???

48V
Really, the bottom line? Because I was convinced to by Tom at TheSolarBiz.
Smaller wiring runs, more efficiency (theoretically) in the inversion process and also supposedly less wasted energy at the inverter and charge controller.

Have you checked out the Outback forums? MOUNTAINS of information.

I have and part of the reason why I am strongly considering upgrading to 48 volts. I guess I can wire my 24 volt panels in series pairs to get the needed input voltage. Which 48 volt inverter are you using?

Go for the highest voltage available. Inverters are more efficient (less voltage change); higher volts mean lower amps=less line loss, less heat; smaller wire size. Also another thing not previously mentioned is that you can use fewer parallel battery strings which allows fuller charging and better battery life. Hate to tell you to throw away a good inverter just to change voltage, but if you're having trouble with the inverter, I would recomend the higher voltage. I am using Outback products and they seem to be a qauality product with good customer support, however they'er still too new for me to really tell.

We have 24 volt panels and 12 volt batteries. I originally went this way because, at the time, there weren't many options for low watt 110 volt lighting. We planned to use a combination of 12v and 110v lighting. I thought we would be using a lot of 12 volt lights to save on power and I didn't want to deal with running a DC down converter to change 24 or 48 volts to 12 volts for the lighting.

Now there are so many new options for low watt 110 lighting, there's no need to spend the bucks on larger gauge wire to accommodate a 12 volt system, just to run 12 volt lights.

As far as efficiency, I don't think there is a difference if the proper gauge wire is used. If for some reason someone wanted to go with 12 volts, and the proper size wire was used, there would be no difference in charging or conversion efficiency...well maybe a bit of loss from 12v to 110 vs. 48v to 110v, but it's most likely negligible. Remember, even with 48 or 72 volts you have to make sure your wire is sized properly for the run or you will have loss.

If I was starting from scratch though, I would go with the higher voltages, it does save a lot of $$ on wiring.

If it wasn't for my 12 volt inverters I could switch pretty easily, but I've already installed the the larger gauge wire, and replacing my inverters would be very expensive, so as I increase the size of my system, I'm just going to leave it at 12v. Fortunately when I bought and pre-installed all the the wiring, the cost wasn't what it is today.

I have the Outback FX3048 and a FlexMax 60 charge controller.
Two/four solar panel strings and 8/6V batteries.

Originally Posted by soulpatch

I have the Outback FX3048 and a FlexMax 60 charge controller.
Two/four solar panel strings and 8/6V batteries.

If I was just starting out (with what I know now) I would probably have gone with that configuration. Since I already have my PSW inverter I will run with the system at 24 volts for now. I can always reconfigure for 48 volts down the road I suppose...

I don't want high current (>100A) going through wires in the house, even beastly 4/0 copper with heavy paralleled crimp connectors. High voltage is no problem, with 600v rated cable available.

48v inverters are a good middling solution. The only drawback is that 48v is able to put enough current across a person to stop their heart. So be careful and don't work on hot systems alone!

96v DC would be more appealing. I don't know if the parts are cheap enough to make profitable inverters for the masses. Eight 12v batteries in series is about the 500 pounds of cells that makes for useful power. 96v increases efficiency by reducing copper losses and copper install costs, or as an upgrade to a 12v wired system, greatly (8x?) increases system power delivery capability.

Cheers.

Originally Posted by rufus13

I don't want high current (>100A) going through wires in the house, even beastly 4/0 copper with heavy paralleled crimp connectors. High voltage is no problem, with 600v rated cable available.

48v inverters are a good middling solution. The only drawback is that 48v is able to put enough current across a person to stop their heart. So be careful and don't work on hot systems alone!

96v DC would be more appealing. I don't know if the parts are cheap enough to make profitable inverters for the masses. Eight 12v batteries in series is about the 500 pounds of cells that makes for useful power. 96v increases efficiency by reducing copper losses and copper install costs, or as an upgrade to a 12v wired system, greatly (8x?) increases system power delivery capability.

Cheers.

Interesting post and welcome to the forum.

I started building this system before I did all my homework and I probably still will upgrade to 48v at some point. Right now the system is working good and with the extra panels I recently added I am now up to 2kW solar output and the second wind turbine is just waiting for Chava to finish with astrobaja's projects so he can help me get that up as well.

I just cannot say enough as to how much the wind turbine helps keep the batteries up. Since I have added the Bogart Pentametric to the system I can closely monitor the system and my batteries have never gone below 80% in the current setup and rarely below 90%.