Typical set-up for a 48V cabin

Re: Typical set-up for a 48V cabin

Well you'll save a bundle avoiding DC appliances and lights. The off-the-shelf AC stuff is pretty efficient these days and makes the wiring much simpler. You can run 120 VAC further on smaller wire with less loss than any lower Voltage for the same amount of power. The conversion efficiency and tare loss of the inverter is negligible.

I run the whole cabin off a 24 Volt system with 700 Watts of panel, 232 Amp hours of battery, and a Honda EU2000i for when the sun doesn't co-operate. This includes a standard 16 cu. ft. refrigerator, the computer/internet/phone set-up (via satellite), any lights needed at night, water and septic pump, and occasional microwave zap. Load management goes a long ways towards making things efficient.

For example if you use the 'standard' end-to-end formula on my system you get:
700 Watts * 5 hours equivalent good sun * 0.52 over-all efficiency = 1820 Watt hours AC.
But in reality I use around 2400 Watt hours AC. One advantage comes from the 3200' elevation which allows my array & controller to operate at 82% instead of the typical 77%. The rest comes from timing loads to make best use of power the panels are capable of but will otherwise not produce once the batteries are full.

In your case get out the Kill-A-Watt meter and measure your TV viewing and refrigerator consumption. It doesn't matter if these aren't what you'll use at the cabin; you just need an approximation.

When you go up to 48 Volts there are extra costs involved: more batteries to get a 48 Volt system (eight 6 Volt units instead of four) which is necessary whether or not you need the stored power (10.5 kW hours vs. 5.2 kW hours using GC2's). More expensive circuit breakers to interrupt the Voltage (all over-current protection and disconnects have to be able to handle >60 Volts). Inverters for 48 Volt systems tend to start out at large and expensive: Magnum 4.4 kW @ $2,200, Outback 3.0 kW @ $2,000, Conext 4.5 kW @ $2,400. You don't need that big of an inverter to run what amounts to a single outlet (1800 Watts).

So the only caution is: what about expansion? Is there the possibility you may want more power in the future?

And then look at the 'single charge controller' limit based on 80 Amps output @ system Voltage:
800 Amp hours @ 24 Volts is 9.6 kW hours. Although this is quite a large battery bank, it is possible. That's the same as 400 Amp hours on 48 Volts (about two parallel strings of GC2's). Quite a bit of power either way.

Re: Typical set-up for a 48V cabin

Texas Wellman wrote: »

I wonder if something like this http://kingtecsolar.com/products/solarpoweredairconditioner-k25cj-4/ wouldn't work well with that 3.3 KWH system? I'm surprised that we haven't seen any posts or other info about it since it came out about two years ago.

There's a whole thread on that here: http://forum.solar-electric.com/showthread.php?17347-The-Kingtec-K25Z-4-Solar-Air-Conditioner

BTW, you're guessing 3.3 kW hour will do. If you guess wrong, it won't. You really need firmer basis for system sizing then Bill's estimates and your estimations. Try to approximate the conditions at home and measure the power usage. Then try to keep the Mrs. from adding more and more electric gadgets to overtax the system.