I'm looking at a kit like this for emergency backup power. Basicly, I want to run a few LED lights, charge a cell phone and power a small fridge. I know I would need a bank of batteries and I wanted some help in calculating how many to buy. Is there a formula to use that would tell me what I need? I don't know if this makes sense, but I'm thinking that I want 3 days of storage when the batteries are maxed out and don't want my load to exceed one day's storage. Thanks for your thoughts!
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Grape Solar 400-Watt Off-Grid Solar Panel Kit
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Everything you ask for is easy, until you ask for refrigeration. that changes everything, and 400 watts of solar will unlikely cover a refrigeration load. Especially if you plan to use a small dorm refrigerator with an inverter. If you chose chest style unit that runs on native DC power you will save hundreds on batteries and your 400 watts of panels may be enough. Note: Some small convenience refrigerator units can consume as much if not more than a quality full size unit. This kit is not a bargain and with a PWM charge controller, you will get up to 300 watts under ideal conditions. save your money and get a kill a watt AC monitor and figure how much power your refer actually uses first. -
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Logan5, thanks so much for responding. This is my first post here and I know almost nothing about solar. We have a generator now, but that will keep me up for about three days with the propane I have and I would expect that the utilities could be down for a month or two if we have a bad disaster. So you mean something like this for a fridge?:
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That is not a refrigerator and will not be cold but cool. Under extreme conditions that unit may not work at all, and will consume a lot of power @ 12 volts. You should be looking at 24 volt chest style refrigerators, in one of your links there are several good ones, they start around 600 bucks and that is a bargain compared to running an inverter 24X7 to maintain a refrigeration load.
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Logan5, thanks so much for responding. This is my first post here and I know almost nothing about solar. We have a generator now, but that will keep me up for about three days with the propane I have and I would expect that the utilities could be down for a month or two if we have a bad disaster. So you mean something like this for a fridge?:
Knox 48 Quart Electric Cooler/Warmer with Built in Car and Home Plug- on Amazon
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So I have not bought the fridge yet as I know our full size Samsung won't work (lower freezer). So you are saying to go with a small DC unit and don't just buy a smaller AC fridge. We don't want to spend a lot on a solar system as this will be for backup only as we live in the NW and have cheap power. My thought was to spend $1000 on a solar system and $500 on batteries and maybe call that good. I really don't want to go for a $15,000 system and be off the grid or at least I don't think I do.Comment
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So I have not bought the fridge yet as I know our full size Samsung won't work (lower freezer). So you are saying to go with a small DC unit and don't just buy a smaller AC fridge. We don't want to spend a lot on a solar system as this will be for backup only as we live in the NW and have cheap power. My thought was to spend $1000 on a solar system and $500 on batteries and maybe call that good. I really don't want to go for a $15,000 system and be off the grid or at least I don't think I do.Comment
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Thermoelectric is not refrigeration, it will consume a lot of power and seldom cools under 50deg F. in extreme heat this may not work at all and still kill your batteries. Search E-bay for DC refrigeration, 24 volt refrigeration, look for products like Engle, Dometic, Norcold. Everything else is junk.
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Ok, I do have some electrical skill (basic). I understand that I need to go to a 24V DC system. So what is the best brand of panels and inverter? Also what is a MPPT CC? Thank you for the recommendation on 24V fridge brands. So I will be setting up an isolated system in my home and running 24V to lights and the fridge. I was originally planning on having an inverter convert back to 120V AC and then using my same GenTran circuits to power up selected devices. I will switch gears now.Comment
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Ok, I do have some electrical skill (basic). I understand that I need to go to a 24V DC system. So what is the best brand of panels and inverter? Also what is a MPPT CC? Thank you for the recommendation on 24V fridge brands. So I will be setting up an isolated system in my home and running 24V to lights and the fridge. I was originally planning on having an inverter convert back to 120V AC and then using my same GenTran circuits to power up selected devices. I will switch gears now.
The inverter needs to be a Pure Sine Wave type which works better with electronics and AC motors. If you use a DC fridge you do not need a large inverter to handle that as an AC load.Comment
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Logan5, I'm still working on my project. You mentioned "24 volt refrigeration, look for products like Engle, Dometic, Norcold. Everything else is junk.". I'm having a hard time figuring out how many watts these fridges draw. Here is where I am...I have a 400 Watt system and have not set it up yet and have not bought the batteries. It would be easier for me if I kept it a 12V system and not 24v as I'm running a 12v alarm system and a 12v USB charger. So I'm not exactly sure how to ask this but here it goes: How many watts would these fridges draw on 12v and how many on 24v? I assume the two answers are different. I can't find any published material on the details of the low voltage draw.Comment
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I'm new to the forum and want to start a new thread buy only see the "post reply" button. Here is my question: Why would I want to switch a small system to 24v over 12v. I get that you can use smaller wire, but most of my stuff is 12v and then I need to find a way to convert it back to 12 for use if I switch to 24v. I have a 400 watt system and need to buy batteries so I need to know if I'm doing 12v in series or parallel? Also, how large of deep cycle batteries should I be buying for 12v or 24v if I can produce up to 400 watt? The way I'm looking at this is I will not get 400 watts on average and will need to plan on maybe 300 watts for 8 hours. Is my logic right?Comment
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