new solar setup
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Scottish dan
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How many solar panels would I need and what wattage
svetz
Works in theory! Practice? That's something else
So, the next big question is how many cycles do you expect/need? That is, will you be running them only during a power outage (e.g., a few times a year)?
Battleborn LiFePO4s run about a $/Wh, so 4,600 Wh is ~$5,000 just for the battery but it'll last 5000s cycles at 80% depth of discharge (DoD). DIY LiFePO4 batteries are around $0.40/wh, so ~$2300. AGM lead acid is about $0.32/watt-hour with a 50% DoD so about $3000 for 1000 cycles. If you think you'll only need ~30 cycles per year, you could probably run the AGMs for a decade at 90% DoD for ~$1700.
See AGM Question: DOD% vs Life Expectancy and the Battery FAQ for more.
Battleborn LiFePO4s run about a $/Wh, so 4,600 Wh is ~$5,000 just for the battery but it'll last 5000s cycles at 80% depth of discharge (DoD). DIY LiFePO4 batteries are around $0.40/wh, so ~$2300. AGM lead acid is about $0.32/watt-hour with a 50% DoD so about $3000 for 1000 cycles. If you think you'll only need ~30 cycles per year, you could probably run the AGMs for a decade at 90% DoD for ~$1700.
See AGM Question: DOD% vs Life Expectancy and the Battery FAQ for more.
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svetz
Works in theory! Practice? That's something else
True, but planning for a contingency of two days with no sun means you need the 4,600 Wh. Although you might use that to decide on a DoD. That is, you use a 90% DoD for two days with no sun knowing that most of the time you'll get some sun so have a lower DoD. So, it's a trade off of costs versus cycle life.
Scottish dan
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Scottish dan
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Or would 24 volt be better
svetz
Works in theory! Practice? That's something else
Wow! Nice price for a drop in!
A 24V system might have a slightly higher inverter efficiency. Mainly it's choice of $. For example 2400W at 12 volts is 200 amps, at 24V it's only 100 amps... so you might be able to use a less expensive wire gauge at 24V. But you might find a better price on a 12V inverter. So, for me it's the kind of thing I have to run the cost numbers both ways to make the decision.
A 24V system might have a slightly higher inverter efficiency. Mainly it's choice of $. For example 2400W at 12 volts is 200 amps, at 24V it's only 100 amps... so you might be able to use a less expensive wire gauge at 24V. But you might find a better price on a 12V inverter. So, for me it's the kind of thing I have to run the cost numbers both ways to make the decision.
Scottish dan
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Wires not an issue as I work in construction and can get it for free. I am thinking of the mppt epever charge controller
Scottish dan
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So would I need a 3000 watt inverter
mandrews44
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You only need 500wh overnight? (Not including backup?)
mandrews44
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Without considering the 2 days without sun which should be load*3 in real-life, I'm showing a 400ah battery before calculating the night vs day usage.
mandrews44
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I finally had time to run the calculations.
Minimal load per day: 2,443 watts
Minimal solar panels necessary: 600 watts
Average Load: 206 watts
Inverter needed: 500 watt (to save power), 1,000w depending on fridge surge.
Backup time for 2 realized days on backup: 64 run hours or 6,515 watts. (650ah)
Backup time for 1 realized day on backup: 40 run hours or 4,072 watts. (400ah)
Battery 2 day backup: 650ah.
Battery 1 day backup: 400ah.
Battery 0 day backup: 150ah.
I used LiFePo4 as the battery beause it does not require full charges, offers the longest life and is the least damanged for going below 30%. These calcuations are with the battery going down to 20% for each cycle.
In this configuration, the sun goes down today (Tuesday) and you will have remaining backup power until Friday Morning. (2 full days without Solar Energy). I am assuming you are getting a yearly average of 5.5 hours of sun per day. You can search on google for your location and get your average sun hours. I suggested a 500w inverter because your max load is just over 200 watts and a 2000w inverter, even with low power mode will draw 1 to 2 amps under no load so that also has to be added in. (24 - 48 amp hours if not used and has to be added to the total load). I included 156 watt hours for the inverter.
assuming 5.5 hours, using a MPPT charge controller, you should yield 3.3 kw hours with just under that daily load. I would also consider the minimal or average days of sunlight. I get anywhere beween 4 and 10 charge hours and to cut it this close, you will need to know your average and how many days in a stretch you get much less than normal. For those days, a backup to the backup might be necessary.
There are still too many unknowns for a definate answer but this is a good start.
Questions?
Minimal load per day: 2,443 watts
Minimal solar panels necessary: 600 watts
Average Load: 206 watts
Inverter needed: 500 watt (to save power), 1,000w depending on fridge surge.
Backup time for 2 realized days on backup: 64 run hours or 6,515 watts. (650ah)
Backup time for 1 realized day on backup: 40 run hours or 4,072 watts. (400ah)
Battery 2 day backup: 650ah.
Battery 1 day backup: 400ah.
Battery 0 day backup: 150ah.
I used LiFePo4 as the battery beause it does not require full charges, offers the longest life and is the least damanged for going below 30%. These calcuations are with the battery going down to 20% for each cycle.
In this configuration, the sun goes down today (Tuesday) and you will have remaining backup power until Friday Morning. (2 full days without Solar Energy). I am assuming you are getting a yearly average of 5.5 hours of sun per day. You can search on google for your location and get your average sun hours. I suggested a 500w inverter because your max load is just over 200 watts and a 2000w inverter, even with low power mode will draw 1 to 2 amps under no load so that also has to be added in. (24 - 48 amp hours if not used and has to be added to the total load). I included 156 watt hours for the inverter.
assuming 5.5 hours, using a MPPT charge controller, you should yield 3.3 kw hours with just under that daily load. I would also consider the minimal or average days of sunlight. I get anywhere beween 4 and 10 charge hours and to cut it this close, you will need to know your average and how many days in a stretch you get much less than normal. For those days, a backup to the backup might be necessary.
There are still too many unknowns for a definate answer but this is a good start.
Questions?
