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Off Grid Power Supply and Demand
Are you trying to move Off Grid and you seem to have run into a wall when it comes to accurately calculating how many Watts your Battery Bank is able to produce VS how many you are going to use. Well, it’s a pretty simple equation: Amperes x Volts = Watts. You multiply your AMP output by your Voltage output and that gives you the Watts that your power source is able to produce for you to use.
For example, if you have a row of batteries running to an inverter for 120VAC from 12VDC, and it pulls 100 amps of power, you would have something that looks like this:
So, you would have 100x12=1200 watts of power. Depending on what you are running, and how many AH you have, you could make an accurate assumption on how long you can draw 1200 Watts of power.
Now that you can accurately find how many watts you are able to produce you might want to look at charging options. You can look at SOLAR Panels\ Wind Power. If you want to charge during the day with little or no draw, and are located in a decently sunny area, then you could go for SOLAR Panels. If you’re in a valley with a moderately windy area, you should look into Wind power.
When charging with Solar panels it is best to take into consideration how many AH you have? If you have 300 and want to charge your batteries fairly quickly using solar panels, they must have a rating of at least 30% to quick charge your power bank. That would be overly expensive and not very cost effective. So, we’ll look at Wind power. You have plenty of wind and the know how to make a simple wind generator. These are more than capable of producing and OVER charging your battery bank, so, when used to ‘Quick charge’ your power supply, keep in mind the power output produced by your wind generator. Let’s face it, you don’t want to blow up your batteries and waste all that money and time. You need to look into a Charge Converter to sense when your batteries are fully charged and switch the power being produced by your charging system to a dead end or an appliance that you will use later on, such as a water heater.
To find out how many watts you’ll need during the evening and night hours, to calculate how big of a Battery Bank you need, make a note of all things you might or will use during the evening such as: reading lights, water pumps, radios, DC TV, 12Volt Heaters, and microwave ovens. All of these you might use during the evening hours so you will want to have an excess of power. After all, when you have more than you can use you are safe; when you need it and don’t have it, that’s when you run into problems. So, now that you have made a list of things you will be using, or might use, during the evening, you can find out how many Amp Hours of power you will be using, and how many you MUST have to make it through an average night.
To find out how many AH you will be using, follow this formula: AMPS being used (the constant AMP draw over a period of time) multiplied by your duration of use. So, for this we’ll use 10Amps or 10A. Now, you multiply by your duration of use, for instance 8 hours. So, now your equation should look like this: 10A x 8Hrs = 80AH. If you have a 120VAC converter you would do this for a 12Volt battery bank: 120 ÷12 = 10 x your AH usage for that 8 hrs. Now, lets clean this up a bit: (10A x 8Hrs = 80AH) x (120V** ÷12v***= 10). So you have 80 x 10 = 800AH of power actually being used. With this many AHs being drained you need at least a 1000 AH rating. That’s a lot but it is just an example.
120V** is the voltage your inverter turns 12v*** into.
Now, lets have an overview. You take your Amp draw times the duration of the draw gives you the AMP hours used. To find total power consumed you divide the Voltage made by the Inverter by the Voltage the Battery Bank is wired for. Now after dividing those two you multiply your AMP hours used and you have the total power consumed.
It’s a little confusing if you think about it, however it is very simple and I hope that I have explained it straight forwardly enough.