Newbi off grid

[Nimrod5]

The long term goal is to have an off grid homestead. I have made the following progress so far; I paid cash for an off grid 40 in north central MN, I hammered in a sandpoint and power it with a genny, I put in a propane fired hot water heater so I have hot showers, I built a barn, and I have a camper. I spend a lot of time there in the summer. I would spend more time there if I had an air conditioned room in the barn to get out of those 100 degree 70 dew point days and nights. I am still paying off part of the barn so money is very tight.

I was recently gifted six 265 watt solar panels and a Midnight Solar Kid charge controller. It's brand new equipment that's been stored for the last 8 years. I know that 1590 watts of solar is a small system by today's standards but I would like to see if it can run a 5000 BTU window AC. I plan to follow the system in the Kid's instructions, 2 strings of 3 panels wired in series and the strings wired in parallel. I need to buy a 48 volt battery bank, some wire, breakers, and an inverter. The batteries will be lead acid because I'm broke and because they will get to -40 during the winter while I'm not there.

Are the inverters from companies with names composed of random letters (are they government alphabet agencies?) any good? Will a 4000 watt cheap pure sine wave inverter handle the start up surge from the AC? It normally uses 450 watts.

Does the following sound right to you? The battery bank will be 48 volts and 100 amp hours of lead acid. It only gets really hot on sunny days so The AC will be on when the panels are putting out the max wattage until dusk when the batteries have to take over. If the batteries get fully charged during the morning then they will have 2400 watt hours for after dark so the batteries only drain 50%. This is enough to run the AC for 5 hours and by that time the evening will have cooled down. It looks like this will work.

 

[sunshine_eggo]

You're getting a little ahead of yourself. You have a goal. Design for it. Don't guess. You're not horribly far off, but planning right helps you get it right without investing too much $$ or falling short.

Link #1 in my signature - determine your available solar and energy needs; PVWatts site and the energy audit.

You would probably do well to invest in a Midea high efficiency window unit or small mini-split with an inverter compressor to avoid the surge and get the most out of what you have. They operate MUCH more efficienciently, and they modulate their output, i.e., they maintain a temperature by running at lower power rather than cycling between 100% and 0% periodically.

 

[Nimrod5]

Thank you for replying. As stated money is very tight. I already have the panels, charge controller, and AC unit. No money to buy others. The question remains, are the cheap pure sine wave inverters any good and will they provide enough surge to start the compressor in the AC? Will the system, as stated, provide enough to run the AC till about midnight?

 

[sunshine_eggo]

Thank you for replying. As stated money is very tight. I already have the panels, charge controller, and AC unit. No money to buy others. The question remains, are the cheap pure sine wave inverters any good and will they provide enough surge to start the compressor in the AC? Will the system, as stated, provide enough to run the AC till about midnight?

Surge of the cheap units is a joke. You'll need at least a 4000W continuous rated one for certain. WZRELB is also known as "Reliable," and they're generally pretty decent. Giandel is a popular brand with Will.

As proposed, you will likely be able to count on 8-10 total run hours per day assuming unshaded panels from sunrise to sunset. Depending on ambient and your insulation, you might get as much as 14 hours.

 

[Nimrod5]

Thanks for the info.