Solar off-grid Calculator using batteries

Simulador fotovoltaico isolado off-grid com baterias

Att. : existe conversor AC para DC na última parte desta página

AC = Alternating Current (ex. 230V) ; DC = Direct Current (ex. 12V)

  Calculation Type Description Units  
Estimated Watt demand
3 Total Watts Per Hour (DC) DC Amps x System Voltage Watts
Hours per day
6 Hours Equip is expected to run (24hr) as per application Hrs d-1
Watt-Hours per day
9 Total daily usage Watts x Hours Watt-Hrs d-1  
Amp-hour calculation
10 Total watts Daily requirements Watt-Hrs d-1  
11 Corrected for battery losses Assumes static average loss Watt-Hrs d-1  
12 System voltage DC voltage only Volts
13 Amp-hours per day Watts divided by Volts Amp-Hrs d-1  
Battery bank calculation
14 # of days backup power required Average 24 hour periods days
15 Amp-hour storage Raw capacity you need Amp-Hrs  
16 Depth of discharge Assumes 50% fraction (enter decimal) 0.5
17 Required amp backup Prevents excessive discharge Amp-Hrs  
18 Battery Amp Rating (20 hr) Battery Capacity in Amps fraction
19 Actual # batteries wired in parallel Raw number number  
20 Batteries wired in series Relates to system voltage number  
21 Rounded number of Batteries Always rounded up number  
Solar Panel Array calculation
22 Sun hours per day (Direct only) Be realistic! Hrs
23 Worst-weather multiplier* 1.55 default fraction
24 Total sun hours per day Assumes average sun Amp-Hrs  
25 Select panel size (Watt rating) Watt hour rating Watts
26 Nominal Panel Voltage Approximate Solar output Volts 16
27 Amps required from solar panels Total daily consumption Amps 15
28 Peak amperage of solar panel Watts divided by Volts Amps  
29 Number of solar panels in parallel Raw Number number  
30 Number of panels in series (12 V) it is 1 for 12v, 2 for 24v, etc number  
31 Rounded number of solar panels Always rounded up number  

Solar Calculator Notes and Instructions and Disclaimer.

First, the notes: We hope this solar calculator will make sizing your panels and batteries a little less painful. Keep in mind that this is only a calculator, and it will directly reflect whatever you, the user, inputs into the fields.

If your base calculations are off by even a little bit, the results reflected can be skewed by quite a bit, so view this as a guide, not an absolute.

With that said, here comes the disclaimer :
This calculator is for educational purposes only. is in no way responsible for the results of your calculations, and if you purchase a system based on the results of the Solar Calculator, will not and cannot be held responsible for returns or exchanges for improperly sized systems.
Normal guarantees and exchange rules will apply to all solar panel purchases.

Now the instructions:

Field #3: This field needs to be DC watt draw only. If you are using an inverter, meaning your device is rated in AC amps and 110 V, you will need to convert that number into DC watts before entering it in the field. Then you will need to add about 10% due to the inefficiency of the inverter. To get there, use the following formulas;

1 Amp AC = 10 Amps DC. (example, 2AC amps = 20DC amp)

Add 10% (22 amps)

DC amps x 12v = DC watts. (22 x12 =264 watts)

264 would be entered in field # 3

Fields #6 and #12 are for how many hours you expect your equipment to run in a 24 hour period, and your input voltage (12, 24, 36?).

Fields #14 and #18 will determine what size and how many batteries you need. In #14, insert days of backup you would like your battery pack to be good for. This is minus any solar panels, which we will figure in a minute. Field #18 is based on what battery you choose. Say you want to use a 55 AH battery because you like the dimensions, or maybe you like the 21 AH battery due to its terminal configuration. Enter your chosen battery amps there. We don’t like to see any battery discharged more than about 50%, so we will automatically adjust for that.

Still with me? Good, we are almost done. The last two fields, #22 and #25 are easy. How many hours of direct sunlight do you estimate your panel will get. Be realistic. We will then automatically guesstimate for clouds, bad weather etc. Field #25 is just like field #18 in the battery section. Look at our solar page, pick a panel you like and then enter the watts here.

Calculator | DC to AC
amperage conversion run through an Inverter

So, you’ve got an electrical appliance to run, but no place to plug it in. When you need to run a regular household electrical type device in an area where no regular grid power is available, this calculator will help you figure out what size batteries and inverter you need!

Welcome to our DC/AC conversion tool (with inverter). This calculator is designed to assist you with power usage amounts, when converting from one power form to another using a DC to AC inverter. Just enter power numbers in the fields below, and we will do the calculations for you, including typical inefficiencies and all that other techie type stuff you may not care to calculate. If you are not sure of your numbers, have a look at the walkthrough illustrations below when entering numbers.

Enter AC Device Ratings
AC Voltage VAC
AC Amperage Amps AC (enter mAh as .xyz)
Wattage 0 Watts
DC Voltage   12 V     24 V     36 V     48 V
DC Amperage 0 Amps DC



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AC Voltage - Many applications will have a range of Input AC voltage. In the US, it can be anywhere from 100-125 VAC. In Europe, it's usually 200-240. For this example, we'll use the US standard of 120 Volts AC.

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AC Amperage - Input Amperage is how much current the application draws from the AC power. This number is usually rated in Amps. If the current is rated in milliamps (mAh) you can convert it to Amps by diving the number by 1000. For instance, our example application draws 300 milliamps, which is the same as 0.3 Amps.

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Wattage - Wattage is the total amount of power the application uses. It's calculated by multiplying voltage by amperage. Therefore the 120 VAC x 0.3 Amps equals 36 Watts.

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DC Voltage - Output Voltage is rating of your battery system, usually a single 12 volt battery. We use 12.5 volts for 12 volt battery systems.

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DC Amperage - Now we know that our application uses 36 watts of total power. If you take this power from a 12.5 VDC source, then the total amperage required increases to 3.31 Amps, or 3,310 milliamps. Since batteries have a limited capacity, or amp hours, it's important to size a battery large enough to handle the amperage demand for your application.

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