Sizing a battery bank. Ah VS wh?
Hi again! So, I'm trying to size out the battery bank I will need for my husband and I to live off grid in a camper. We don't have tons of time or money, so that's a bit of a factor. We plan on usi...
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Low budget and running an entire RV off grid just don't go together. Batteries are quite expensive right now and getting worse. Inverters, generators, and gas are also expensive.
You can figure amp hours or watt hours, which ever is easier. I tend to use watt hours. Either way that's a big heavy expensive battery bank. 2510 WH per day is a lot. You would need at least twice that in battery capacity bare minimum if you want your batteries to survive so that's 5020 AH. With 12 volt batteries that's 418 AH. You could use 4 6v golf cart batteries wired in series/parallel to get that capacity. I would recommend going larger because draining your batteries to 50% every day is still rather hard on them. Further, if you have a couple cloudy days in a row and the solar isn't producing much you either have to run the generator or have a battery bank big enough to last thru the cloudy days. Most people figure on a battery bank big enough for 3 days of no sun. If you do this you will need over 1,200 AH. Now you're getting into a size that really needs to be done with 2v batteries in series. Something like a Rolls battery.
In order to put back roughly 5 kWh a day with solar panels in the winter in VA you will need about 1,500 watts of perfectly oriented panels; that is set to a tilt angle of 45 degrees and pointed due south. Again, this is bare minimum, more solar would be better.
A $275 generator is a piece of junk. It might be fine for someone who only needs it once a year to power their refrigerator during an 8 hour power outage. You'll need to run a generator for at least 4 or 5 hours a day every day to keep up with your demand if it's cloudy or snow is covering your panels. With the price of gas what it is it won't take long for a higher quality more fuel efficient generator to pay for itself.
You can figure amp hours or watt hours, which ever is easier. I tend to use watt hours. Either way that's a big heavy expensive battery bank. 2510 WH per day is a lot. You would need at least twice that in battery capacity bare minimum if you want your batteries to survive so that's 5020 AH. With 12 volt batteries that's 418 AH. You could use 4 6v golf cart batteries wired in series/parallel to get that capacity. I would recommend going larger because draining your batteries to 50% every day is still rather hard on them. Further, if you have a couple cloudy days in a row and the solar isn't producing much you either have to run the generator or have a battery bank big enough to last thru the cloudy days. Most people figure on a battery bank big enough for 3 days of no sun. If you do this you will need over 1,200 AH. Now you're getting into a size that really needs to be done with 2v batteries in series. Something like a Rolls battery.
In order to put back roughly 5 kWh a day with solar panels in the winter in VA you will need about 1,500 watts of perfectly oriented panels; that is set to a tilt angle of 45 degrees and pointed due south. Again, this is bare minimum, more solar would be better.
A $275 generator is a piece of junk. It might be fine for someone who only needs it once a year to power their refrigerator during an 8 hour power outage. You'll need to run a generator for at least 4 or 5 hours a day every day to keep up with your demand if it's cloudy or snow is covering your panels. With the price of gas what it is it won't take long for a higher quality more fuel efficient generator to pay for itself.
